CC SR 20220517 02 - Traffic Calming on Hawthorne Blvd Near Vallon DrCITY COUNCIL MEETING DATE: 05/17/2022
AGENDA REPORT AGENDA HEADING: Regular Business
AGENDA TITLE:
Consideration and possible action to implement traffic calming strategies for Hawthorne
Blvd. between Crest Rd. and Via Rivera.
RECOMMENDED COUNCIL ACTION:
(1)Review the Traffic Safety Committee’s recommended traffic calming measures
described in the KOA Traffic Study for Hawthorne Blvd. between Crest Rd. and
Via Rivera; and,
(2)If deemed acceptable, direct Staff to implement the short-term traffic calming
measures on Hawthorne Blvd. between Crest Rd. and Via Rivera , monitor their
effectiveness for a period of one year after implementation, and return to the City
Council with a status update and, if necessary, a recommendation to consider
implementing the medium-term and/or long-term traffic calming measures
FISCAL IMPACT: The Fiscal Year 2021-22 CIP includes an appropriation of up to
$695,000 for City-wide traffic calming measures which would be
used to fund this project. Cost estimates for implementation are in
the process of being developed, and in the interest of immediate
implementation as recommended by the Traffic Safety Commission,
the proposed traffic calming measures are being presented for
consideration while cost estimates are being finalized.
Amount Budgeted: $695,000
Additional Appropriation: $0
Account Number(s): 220-400-8846-XXXX ($615,000)
(Measure R Fund – various accounts)
330-400-8846-XXXX ($80,000)
(CIP Fund – various accounts)
ORIGINATED BY: Ramzi Awwad, Public Works Director
REVIEWED BY: Same as above
APPROVED BY: Ara Mihranian, AICP, City Manager
ATTACHED SUPPORTING DOCUMENTS:
a.KOA Traffic Study for Hawthorne Blvd. from Crest Rd. to Via Rivera (page
A-1)
b.Link to April 25, 2022 Traffic Safety Committee Meeting
c.Link to February 7, 2022 Traffic Safety Committee Meeting
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BACKGROUND:
Public Works received requests from the La Cresta Homeowners Association (HOA) to
investigate the traffic and roadway conditions on southbound Hawthorne Blvd. in the
vicinity of Vallon Dr. The HOA expressed numerous concerns regarding speeding and
crashes that occurred in the vicinity of the intersection of Hawthorne Blvd. and Vallon Dr.
Public Works scoped a traffic study to address these concerns and the Traffic Safety
Committee (TSC) recommended that the traffic study be expanded to include the
segment of Hawthorne Blvd. between Crest Rd and Via Rivera.
As a result, Staff hired a traffic engineering consultant, KOA, to prepare a traffic study
evaluating existing traffic conditions and recommending traffic calming measures for the
City’s consideration (Attachment A).
Staff presented the analysis of the subject area and resultant short-term, medium-term,
and long-term traffic calming measures to the TSC on February 7, 2022 (Attachment C).
The TSC and community members provided feedback on the proposed traffic calming
measures. The HOA also identified inconsistencies in the crash data, particularly with
some crashes that the community had known to have occurred that were not included in
the report. Staff reconciled the Public Works Department crash records with the LACSD
crash records and returned to TSC on April 25, 2022 with a corrected report.
The TSC again reviewed the matter at its April 25, 2022 meeting (Attachment B). The
TSC heard public speakers and discussed the recommended measures. As a result, the
TSC passed a motion to recommend to the City Council the approval and immediate
implementation of short-term measures followed by monitoring and the future
consideration of implementing medium- and long-term measures as deemed necessary.
DISCUSSION:
The HOA’s traffic and roadway concerns were primarily for the southbound direction of
Hawthorne Blvd. approaching Vallon Dr., and are summarized below:
•Crashes at the intersection;
•Speeding;
•Red light running;
•Limited visibility at the curb;
•Distracted driving;
•Rapid brake maneuvering during the onset of the yellow/red interval; and
•High-speed southbound right-turn movements from Hawthorne Blvd. onto Vallon
Dr.
To understand the existing conditions and traffic characteristics of the area in question,
KOA was hired to prepare a Traffic Study (Attachment A). As part of the preparation of
the Traffic Study, and to collect feedback and better understand the reported concerns,
representatives from the City and KOA conducted an in-person site visit at the intersection
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of Hawthorne Blvd. and Vallon Dr. with residents and members of the HOA. Additionally,
the president of the HOA provided several video recordings of various traffic crashes that
occurred near the intersection of Hawthorne Blvd. at Vallon Dr., which were carefully
reviewed by City Staff and KOA.
The City Council is being asked to consider the TSC’s recommendations supporting the
proposed short-term traffic calming measures identified in the KOA Traffic Study, as
discussed below.
1.KOA Traffic Study
The Traffic Study prepared by KOA analyzes various information including traffic volume
and speed, crash history, available sight distance, and roadway curvature, and provides
recommended mitigation measures, as discussed below.
Traffic Volume and Speed:
Traffic volume and speed count data was collected over a 48-hour mid-week period on
Hawthorne Blvd. between Crest Rd. and Via Rivera from June 22, 2021 to June 23, 2021.
Table 1 shows the traffic volume and speed data by roadway segments along Hawthorne
Blvd. between Crest Road and Via Rivera.
Table 1 – Traffic Volume and Speed Data on Hawthorne Blvd Between Crest Rd and Via Rivera
Hawthorne Blvd Segment 24-Hour Average
Traffic Volume
Speed
Limit
Southbound
85th Percentile
Speed
Northbound
85th Percentile
Speed
Crest Road to Dupre Drive 14,625 45 mph 45 mph 52 mph
Dupre Drive to Vallon Drive 13,072 45 mph 47 mph 49 mph
Vallon Drive to Via Rivera 13,942 45 mph 48 mph 54 mph
The 85th percentile speed for the northbound direction exceeds the speed limit for all
segments of Hawthorne Blvd. within the study area. The 85th percentile speed for the
southbound direction exceeds the speed limit between Dupre Dr. and Via Rivera.
Crash History:
The crash history for the roadway segment from Ryan Park to north of the intersection
with Vallon Dr., and for the intersection of Hawthorne Blvd. and Vallon Dr. was evaluated
as this location was the primary concern for the HOA.
a.Hawthorne Blvd. from Ryan Park driveway to north of Vallon Dr.:
The crash rate for the roadway segment from the Ryan Park driveway to north of the
intersection with Vallon Dr. was analyzed. The analysis was based on data directly from
the Los Angeles County Sheriff’s Department Lomita Station (LACSD) to assure that the
Public Works Department’s records were complete. This crash rate is separate from the
crash rate at the intersection of Hawthorne Blvd. and Vallon Dr., which will be discussed
later in this report.
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The historical crash rate for this segment, encompassing the total time period for which
data is available (January 2012 to September 2021) was calculated. There was a total of
11 crashes, which equates to 1.18 crashes per million vehicle miles traveled.
A recent pattern crash rate, encompassing the most recent three-year period for which
data is available (October 2018 to September 2021) was also calculated. A three-year
period was used because it is the industry standard time interval for recent pattern crash
rates. The recent pattern crash rate is 1.75 crashes per million vehicle miles traveled.
The average statewide crash rate for four-lane, divided highways of similar characteristics
is 2.04 crashes per million vehicle miles traveled, per Caltrans’ Collision Data on
California State Highways last published in 2018.
Both the historic and the recent pattern crash rates are below the statewide average crash
rate.
Figure 1 on the following page is the crash diagram for all crashes between January 2012
to September 2021 on Hawthorne Blvd. approaching Vallon Dr.
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Figure 1 – Crash Diagram for Hawthorne Blvd. approaching Vallon Dr. from January 2012 to September
2021
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b.Intersection of Hawthorne Blvd. at Vallon Dr.:
The crash rate for the intersection of Hawthorne Blvd. at Vallon Dr. was analyzed. The
analysis was based on data directly from the LACSD to assure that the Public Works
Department’s records were complete.
The historical crash rate for this intersection, encompassing the total time period for which
data is available (January 2012 through September 2021) was calculated. There was a
total of 23 crashes, which equates to 0.417 crashes per million vehicles entering the
intersection.
A recent pattern crash rate, encompassing the most recent three-year period for which
data is available (October 2018 to September 2021) was calculated. A three-year period
was used because it is the industry standard time interval for recent pattern crash rates.
The recent pattern crash rate is 0.824 crashes per million vehicles entering the
intersection.
In addition to the crash data from the LACSD, the HOA provided video evidence of more
recent crashes. There were three crashes that occurred between October 2021 and
March 2022. Staff and KOA carefully analyzed videos of these crashes (along with the
videos of all the other crashes provided by the HOA) for any information about apparent
driver behavior and contributing factors to the crashes. If the recent pattern crash rate is
expanded to March 2022 and the three crashes evidenced by the HOA are included, the
recent crash rate becomes 1.00 crashes per million vehicles entering the intersection.
The average statewide crash rate for four-legged, signalized intersections in suburban
areas is 0.420 crashes per million vehicles entering an intersection, per the Caltrans’
Collision Data on California State Highways last published in 2018.
The historic crash rate is below the statewide average crash rate; however, the recent
pattern crash rate is above the statewide average crash rate and even more so when
extending the time period to March 2022.
Figure 2 on the next page is the crash diagram for all crashes between January 2012 to
September 2021 at the intersection of Hawthorne Blvd. and Vallon Dr. Figure 3 on the
following page is the crash diagram for confirmed crashes between September 2021 and
March 2022 at the intersection of Hawthorne Blvd. and Vallon Dr.
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Figure 2 – Crash Diagram for Hawthorne Blvd. at Vallon Dr. from January 2012 to September 2021
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Figure 3 – Crash Diagram for Hawthorne Blvd. at Vallon Dr. from October 2021 to March 2022
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Sight Distance:
a. Intersection Sight Distance
Intersection Sight Distance (ISD) represents the sight line distance needed for a driver
leaving the intersection to have enough time to see that the road is clear , then leave the
intersection while allowing an oncoming vehicle sufficient time to prevent a crash.
The ISD at the intersection of Hawthorne Blvd. and Vallon Dr. was analyzed only for right-
turning vehicles on Vallon Dr., which can proceed after coming to a full stop under a red
signal phase. Left-turn movements from Vallon Dr. were not analyzed because such turns
can only occur when a green light is given. The recommended engineering standard ISD
for right-turning vehicles on Vallon Dr. is 430 feet.
The left-hand sight distance for motorists on Vallon Dr. stopped behind the existing limit
line does not meet the recommended minimum sight distance for right-turn on red
movements with the potential to conflict with oncoming southbound traffic on Hawthorne
Blvd. However, motorists wishing to turn right on the red indication typically proceed
slowly and cautiously into the intersection in order to increase their sight lines. Under this
typical scenario, the recommended minimum sight distance is met. California case law
has ruled that the practice of stopping at the limit line and then “creeping” forward to a
point of visibility has long been recognized as “practical”.
Exhibit 1 on the following page shows the ISD diagram.
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Exhibit 1 – Intersection Sight Distance for Hawthorne Blvd. at Vallon Dr.
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d. Stopping Sight Distance:
Stopping Sight Distance (SSD) represents the sight line distance needed for a driver to
view a potential conflict in the road ahead of them and have enough time to prevent a
crash.
The recommended engineering standard SSD to see the signal at Vallon Dr. from the
center of the inside southbound lane of Hawthorne Blvd. is 427 feet and the available
SSD is 530 feet.
Adequate SSD is available for southbound traffic on Hawthorne Blvd. to see the traffic
signal. Exhibit 2 shows the SSD for southbound Hawthorne Blvd. approaching the signal
at Vallon Dr.
Exhibit 2 – Stopping Sight Distance for Hawthorne Blvd. approaching the signal with Vallon Dr.
SSD was also calculated on Hawthorne Blvd. along the inside of the curve between the
driveway at Ryan Park and the Vallon Dr. intersection. The recommended SSD to see an
obstruction in the roadway on Hawthorne Blvd. while driving along this curve is 325 feet;
however, only 270 feet of sight distance is available. The constraining factor for the SSD
along the inside of the curve is a boundary wall and the geometric conditions of the road,
both of which would be impractical to change. In such cases, traffic engineering practice
is to reduce the travel speed.
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In order to satisfy the minimum SSD along the curve, the KOA Traffic Study recommends
changing the curve advisory speed from 35 mph to 30 mph.
Roadway Curvature:
A curve advisory speed analysis was conducted to determine if the existing roadwa y
curve and speed warning signs are appropriate for the prevailing speeds and geometric
conditions. Based on engineering guidance manuals, the analysis concluded that it would
be appropriate to replace the existing 35 mph curve speed advisory postings with 30 mph
curve speed advisory postings to notify southbound motorists of the speed at which to
traverse the curve approaching the Vallon Dr. intersection. This recommendation
coincides with the recommendation to satisfy the minimum SSD along the curve as
described previously.
Recommended Traffic Calming Measures:
Based on the Traffic Study (Attachment A), KOA proposes, the TSC and Staff
recommend, that the City Council consider implementing a series of short-term traffic
calming measures, followed by a monitoring and assessment period and subsequent
consideration of medium-term and long-term traffic calming measures in an incremental
fashion, should they be needed. The recommended measures are listed and discussed
below.
Short-Term Traffic Calming Countermeasures (See Exhibit 3)
1. Install 3-inch wide yellow reflective border strips on all southbound signal heads
at the Hawthorne/Vallon signal to enhance the long-distance visibility and overall
conspicuity of the traffic signal.
2. Install yellow reflective barrier-mountable delineators along the inside/left-hand
side of the concrete median barrier in the southbound direction on Hawthorne
Blvd., along the curve approaching Vallon Dr., to improve the nighttime visibility
and delineation of the median barrier
3. Revise the existing curve advisory speed signs and pavement markings on
southbound Hawthorne Blvd. to reflect a lower speed advisory along the curve
as follows:
a. Replace existing 35 MPH signs and markings with 30 MPH signs and
markings.
b. Replace the existing post-mounted chevron/right-arrow placards (5 signs
spaced at ±150’ intervals in the median) with nine chevron placards spaced
closer at 80’ intervals.
4. Supplement the existing marked crosswalks at the Hawthorne/Vallon intersection
with high-visibility white thermoplastic “ladder” type crosswalk pavement
markings to improve pedestrian visibility.
5. Install “Right Turning Vehicles Yield to Peds” signage on the southbound near-
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and far-side signal poles at the Hawthorne/Vallon intersection to enhance driver
awareness of pedestrians potentially crossing the path of right -turning traffic.
6. Relocate the existing “Right Lane Must Turn Right” sign to the actual beginning
of the right-turn pocket in order to better convey the message to drivers regarding
the “Right Lane Must Turn Right” condition.
7. Install dashed yellow centerline extension line across the median break in front
of the southerly driveway at Ryan Park to draw attention to the curved horizontal
alignment and presence of raised median islands.
8. Refresh the existing “SIGNAL AHEAD” pavement markings with retroreflective
thermoplastic.
9. Maintain the ongoing placement of the City’s radar speed feedback trailer in the
southbound direction on the raised median south of th e Ryan Park driveway.
Coordinate with the Los Angeles County Sheriff’s Department to determine
enforcement schedules. Coordinate with Public Works and law enforcement to
install a permanent pole-mounted/solar-powered speed feedback sign at this
location in the existing landscaped parkway on the west side of Hawthorne Blvd.
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Exhibit 3 – Short-term Traffic Calming Measures for Hawthorne Blvd. approaching Vallon Dr. 14
Medium-Term Traffic Calming Measures (See Exhibit 4)
10. Narrow the southbound #2 travel lane along the horizontal curve to 11 feet wide
to reduce errant maneuvers in the curb lane.
11. Relocate the existing advance detection loops approaching Vallon Dr . to further
upstream to better accommodate a 45 mph approach speed. This measure will
improve the ability for the traffic signal controller at Hawthorne Blvd. and Vallon
Dr. to appropriately allocate green time extensions and yellow/red change
intervals to southbound traffic based on the existing posted sp eed limit.
12. Increase the existing through yellow time from 4.5 to 4.8 seconds to provide
additional time to clear the intersection based on the 45 mph posted speed.
13. Add a pedestrian signal with pushbuttons for the east leg /ocean side of the
intersection to provide proper signal indication for pedestrians crossing Vallon
Dr. at the existing marked crosswalk (whereas the other legs of the intersection
currently have pedestrian signals and push-buttons).
14. Increase driver attention to the changing roadway conditions along the curve by
installing transverse rumble strips:
a. Option A – install rumble strips across the travel lanes on a temporary “pilot”
basis (using a modular system) and gauge effectiveness and overall
community acceptance.
b. Option B – installing a rumble strip along the edge of the roadside (by milling
the pavement) to brings attention to drivers veering out of their lane.
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Exhibit 4 – Medium-term Traffic Calming Measures for Hawthorne Blvd. approaching Vallon Dr. 16
Long-Term Traffic Calming Measures (See Exhibit 5)
15. Increase driver awareness of the approaching Hawthorne/Vallon traffic signal at
by installing additional signal and lighting equipment.
a. Install a new signal indication on the southbound nearside direction at
Vallon Dr. and add overhead safety lighting to improve intersection/corner
visibility at night.
b. Replace the existing large traffic signal pole and mast arm at the southwest
corner (facing southbound traffic) with a new pole to accommodate an
additional traffic signal head (for a total of 2 overhead signals for the through
lanes), and re-position the left-turn signal indication more directly in-line with
the existing southbound left-turn lane for improved visibility.
16. Install an overhead flashing warning beacon system, including “SIGNAL AHEAD”
signage and two, 12-inch overhead flashing yellow signal faces. To improve
driver awareness of the upcoming traffic signal.
17. Install street lights along the roadside in the northbound direction to improve
visibility of the outer edge of the horizontal curve and help with minimizing run -
off-road collisions. Glare shields could be included to minimize the impact of
street lighting on adjacent residents.
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Exhibit 5 – Long-term Traffic Calming Measures for Hawthorne Blvd. approaching Vallon Dr. 18
ADDITIONAL INFORMATION:
HOA’s Suggested Traffic Calming Measure
The HOA suggests considering adjusting the timing of the signal at the intersection of
Hawthorne Blvd. and Vallon Dr. with the signal at Hawthorne Blvd. and Dupre Dr./Ryan
Park so that a red signal would appear for southbound vehicles on Hawthorne Blvd. at
the Dupre Dr./Ryan Park signal when a vehicle on Vallon Dr. arrives at the intersection
with Hawthorne Blvd. Subsequently, a green signal would be given to vehicles on Vallon
Dr. once southbound traffic on Hawthorne Blvd. has cleared. After traffic on Vallon Dr.
has cleared the intersection, southbound traffic on Hawthorne Blvd. at Dupre Dr./Ryan
Park would then receive a green signal again.
KOA and Staff do not recommend moving forward with this suggestion because of
potential unintended consequences. Drivers at Dupre Dr./Ryan Park would be stopped
on red with no apparent conflicting traffic, which may lead them to increasing their speed
once they receive a green light in order to make up for perceived lost time. There may
also be an increase in red light violations as drivers attempt to clear the Dupre D r./Ryan
Park signal so they do not have to wait for what they may perceive to be an unnecessary
reason.
Increased Sheriff Enforcement
LACSD has been providing increased enforcement on Hawthorne Blvd. in the vicinity of
Vallon Dr. via overtime patrols. Between April 2021 and April 2022, those overtime patrols
resulted in 92 speeding citations and 5 red light citations. More recently, in A pril 2022, a
total of 22 speeding citations were issued.
CONCLUSION:
KOA determined that the neighborhood concerns about speeding were reasonable in
justifying the consideration of traffic calming measures. Thus, based on the TSC’s
recommendation, Staff recommends implementing the short-term measures identified in
the KOA report and monitoring traffic conditions and driving patterns to determine if
implementation of the medium- and long-term measures are needed.
ALTERNATIVES:
In addition to Staff recommendation, the following alternative actions are available for the
City Council’s consideration:
1. Direct Staff not to implement any measures at this time and to continue studying
the intersection and roadway segment.
2. Direct Staff to implement both the short- and medium-term measures included in
the KOA Traffic Study.
3. Direct Staff to implement the short-, medium- and long-term measures included in
the KOA Traffic Study.
4. Direct Staff to implement certain traffic calming measures.
5. Take other action, as deemed appropriate.
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PLAN FOR HAWTHORNE BOULEVARD FROM
CREST ROAD TO VIA RIVERA
RANCHO PALOS VERDES, CALIFORNIA
MAY 2022
Prepared for:
City of Rancho Palos Verdes
Public Works Department
Prepared by:
2141 W. Orangewood Avenue, Suite A
Orange, CA 92868
T: 714.573.0317 | F: 714.573.9584
www.koacorp.com
JC13039
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CITY OF RANCHO PALOS VERDES | PLAN FOR HAWTHORNE BLVD. FROM CREST RD. TO VIA RIVERA PAGE I
TABLE OF CONTENTS
1.0 EXECUTIVE SUMMARY ............................................................................................................... 1
1.1 Summary of Findings ......................................................................................................................................................... 1
1.2 Hawthorne Boulevard from Crest Road to Via Rivera – Traffic Calming Needs and Goals ................... 2
2.0 EXISTING CONDITIONS AND DATA COLLECTION ............................................................ 4
2.1 Speed Count Data ............................................................................................................................................................... 4
2.2 Traffic Volumes .................................................................................................................................................................... 4
2.3 Field Visit ................................................................................................................................................................................ 5
3.0 ANALYSIS ......................................................................................................................................9
3.1 Traffic Volumes .................................................................................................................................................................... 9
3.2 Speed Surveys ...................................................................................................................................................................... 9
3.3 Collision Analysis .............................................................................................................................................................. 14
3.4 Sight Distance Analysis .................................................................................................................................................. 18
4.0 RECOMMENDATIONS ............................................................................................................ 28
4.1 Recommended Traffic Calming Measures ............................................................................................................. 28
4.2 Implementation ................................................................................................................................................................ 32
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CITY OF RANCHO PALOS VERDES | PLAN FOR HAWTHORNE BLVD. FROM CREST RD. TO VIA RIVERA PAGE II
LIST OF FIGURES
Figure 1.1 – Study Area ...................................................................................................................................................................... 3
Figure 2.1 – ADT Count and Speed Survey Locations............................................................................................................ 6
Figure 2.2 – Existing Conditions and Traffic Controls ............................................................................................................ 7
Figure 2.3 – Existing Vertical Street Profiles ............................................................................................................................... 8
Figure 3.1 – 24-Hour Average Daily Traffic (ADT) Volumes ............................................................................................. 10
Figure 3.2 – AM Only Traffic Volumes (Midnight-Noon) ................................................................................................... 11
Figure 3.3 – PM Only Traffic Volumes (Noon-Midnight) ................................................................................................... 12
Figure 3.4a – Collision Diagram: Hawthorne Boulevard between Dupre and Vallon ............................................. 16
Figure 3.4b – Collision Diagram: Hawthorne Boulevard at Vallon Drive 18
Figure 3.4c – Collision Diagram: Hawthorne Boulevard at Vallon Drive (not on record) 21
Figure 3.5 – Sight Distance Analysis for Vallon Drive and Hawthorne Boulevard ................................................... 25
Figure 3.6 – Existing Available Stopping Sight Distance for Southbound Hawthorne along the Curve 26
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CITY OF RANCHO PALOS VERDES | PLAN FOR HAWTHORNE BLVD. FROM CREST RD. TO VIA RIVERA PAGE III
LIST OF TABLES
Table 2.1- Speed Survey Locations................................................................................................................................................ 4
Table 2.2- Traffic volume Count Locations ................................................................................................................................. 5
Table 3.1 - Speed Survey Summary - ........................................................................................................................................ 13
Hawthorne Boulevard between Dupre Drive & Crest Road ............................................................................................. 13
Table 3.2 - Speed Survey Summary – ........................................................................................................................................ 13
Hawthorne Boulevard between Dupre Drive & Vallon Drive .......................................................................................... 13
Table 3.3 - Speed Survey Summary – ........................................................................................................................................ 14
Hawthorne Boulevard between Crestmont Lane & Via Rivera ....................................................................................... 14
Table 3.4 – Minimum Recommended Sight Distance Based On Vehicle Maneuver .............................................. 23
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Executive Summary
CITY OF RANCHO PALOS VERDES | PLAN FOR HAWTHORNE BLVD. FROM CREST RD. TO VIA RIVERA PAGE 1
1.0 EXECUTIVE SUMMARY
1.1 SUMMARY OF FINDINGS
In response to concerns raised by residents of the La Cresta neighborhood in the City of Rancho Palos
Verdes, KOA Corporation (KOA) was retained by the City (RPV) to perform an analysis of the existing traffic
conditions, and to determine whether the concerns support further consideration to implement traffic
calming and measures. The sections below describe the various data collection, engineering analyses, local
community outreach, and subsequent technical recommendations resulting from the traffic calming study
effort.
Representatives of the City of RPV and KOA organized an in-person site walk at the intersection of
Hawthorne Boulevard and Vallon Drive to meet with residents and members of the La Cresta Homeowners
Association (HOA) to collect feedback and confirm the perceived concerns. KOA organized the field
observations and input provided by the HOA and incorporated it into the development of the traffic calming
plan for Hawthorne Boulevard from Crest Road to Via Rivera.
Relevant traffic data collected by KOA and its sub-consultant were also organized and analyzed to establish
a baseline understanding of residents’ concerns, and to identify existing traffic and roadway characteristics,
such as: average daily traffic (ADT) volume levels, vehicle speeds and documented traffic collision history.
Through the extensive study, it was determined that the neighborhood concerns about speeding were
reasonable in justifying the consideration of traffic calming measures aimed at reducing vehicle speeds and
traffic collisions on Hawthorne Boulevard in the vicinity of Vallon Road at the entrance to the La Cresta
neighborhood.
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Executive Summary
CITY OF RANCHO PALOS VERDES | PLAN FOR HAWTHORNE BLVD. FROM CREST RD. TO VIA RIVERA PAGE 2
1.2 HAWTHORNE BOULEVARD FROM CREST ROAD TO VIA RIVERA
The La Cresta Community consists of a developed residential neighborhood serving 114 single-family
households located between Hawthorne Boulevard to the south, and Robert E. Ryan Community Park to
the north. Access to the community is provided at Vallon Drive, which intersects with Hawthorne Boulevard
at a signalized intersection. See Figure 1.1 for a map of the study area.
The goals of this study are as follows:
· Identify and analyze ongoing traffic concerns affecting the neighborhood, based on an assessment
of measured vehicle volumes, speeds, field observations, and resident input and feedback;
· Recommend traffic calming measures to mitigate the traffic concerns to appropriate levels that are
consistent with the City’s goals, policies, and standards; and
· Prepare a Traffic Calming Plan for Hawthorne Boulevard from Crest Road to Via Rivera documenting
the existing conditions, data collection, engineering analysis, community outreach, and conceptual
plans and cost estimates to implement the recommended traffic calming countermeasures.
Through community engagement efforts, residents in La Cresta Neighborhood voiced their concerns to the
City about perceived traffic and safety issues in the area, notably at Vallon Drive, which serves as the only
access point into and out of the neighborhood from Hawthorne Boulevard. After a detailed analysis and a
series of discussions with the City of Rancho Palos Verdes staff and the affected residents of the La Cresta
neighborhood, a series of short-, medium- and long-term improvements were developed. Refer to Section
4 for the recommended traffic calming measures.
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Executive Summary
CITY OF RANCHO PALOS VERDES | PLAN FOR HAWTHORNE BLVD. FROM CREST RD. TO VIA RIVERA PAGE 3
FIGURE 1.1 – STUDY AREA
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Existing Conditions and Data Collection
CITY OF RANCHO PALOS VERDES | PLAN FOR HAWTHORNE BLVD. FROM CREST RD. TO VIA RIVERA PAGE 4
2.0 EXISTING CONDITIONS AND DATA COLLECTION
In the vicinity of the La Cresta neighborhood, Hawthorne Boulevard is an 80-foot wide, four-lane divided
arterial with turn lanes in the median. Vallon Drive is a 40-foot wide, two-lane undivided local street serving
the La Cresta community and providing direct access to Hawthorne Boulevard. The posted speed limit on
Hawthorne Boulevard is 45 miles per hour. On-street parking within the study area on Hawthorne Boulevard
is prohibited, except for a 690’ length of curb on the west side of the street between the north and south
driveways, and a 1,900’ length of curb on the east side between Vallon Drive and Dupre Drive. Full street
improvements, including curb, gutter, and sidewalk are provided on both sides of Hawthorne Boulevard.
Beginning at 250 feet north of Vallon Drive, Hawthorne Boulevard aligns along a 500-foot radius curve,
requiring drivers to change direction by approximately 116 degrees over a linear distance of about 935 feet.
Hawthorne Boulevard also contains a significant vertical grade in the vicinity of La Cresta, both to the north
and south of Vallon Drive. The vertical grade, sloping downhill in the southbound direction, averages about
6 percent between Crest Road and Dupre Drive, 9 percent between Dupre Drive and Vallon Drive, and 5
percent between Crestmont Lane and Via Rivera. Figure 2.3 illustrates the elevation profile on Hawthorne
Boulevard in the vicinity of Vallon Drive and the La Cresta neighborhood.
To understand the existing conditions for various traffic characteristics that comprise this evaluation, KOA
collected various data at select locations based on comments received by Traffic Safety Committee from
the La Cresta community, and other correspondences between the City and the La Cresta HOA. The
following sections summarize the data collected as part of this traffic study.
2.1 SPEED COUNT DATA
In order to evaluate whether potential speeding issues exist on Hawthorne Boulevard which affect the La
Cresta community, 24-hour traffic speed counts were collected concurrently for the locations listed below
in Table 2.1 on Tuesday June 22nd and Wednesday June 23rd.
TABLE 2.1- SPEED SURVEY LOCATIONS
2.2 TRAFFIC VOLUMES
Traffic volume field data was gathered during a consecutive two-day period on a typical Tuesday (June 22nd)
and Wednesday (June 23rd) in 2021. The 24-hour average daily traffic (ADT) data was collected using fixed
roadway machine/tube counters placed in the field. These devices register two-way vehicle traffic driving
over a selected point across the traveled way. Counts were taken currently with the speed data, at the same
three (3) locations on Hawthorne Boulevard, listed below on Table 2.2
24-Hour Speed Bin Count Study Locations
1 Hawthorne Boulevard between Dupre Drive and Crest Road
2 Hawthorne Boulevard between Vallon Drive and Dupre Drive
3 Hawthorne Boulevard between Crestmont Lane and Via Rivera
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Existing Conditions and Data Collection
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TABLE 2.2- TRAFFIC VOLUME COUNT LOCATIONS
Traffic Volume Study Locations
Count Type Count Location
ADT Hawthorne Boulevard between Crest Road and Dupre Drive
ADT Hawthorne Boulevard between Dupre Drive and Vallon Drive
ADT Hawthorne Boulevard between Crestmont Lane and Via Rivera
Figure 2.1 illustrates the study locations of the speed measurements.
2.3 FIELD VISIT
KOA staff conducted a site visit at the La Cresta community entrance at Hawthorne Boulevard and Vallon
Drive on Thursday, August 5, 2021. The purpose of the visit was to meet with residents and obtain direct
input regarding the perceived traffic concerns, and to perform a series of observations and measurements
documenting the existing field conditions. The site visit took place in the afternoon between 2PM and 5PM.
During the field visit, KOA documented existing conditions related to the following observable features:
· Turning movements of vehicles on intersection
· Vehicle maneuvers and speeds approaching the intersection
· Drivers’ reaction times at signal
· Sight distance between vehicles at the limit line Vallon Drive, and vehicles approaching the signal
southbound on Hawthorne Boulevard
· Driver/pedestrian behaviors, conflicts, and interactions
· Direction and impact of sun glare against southbound visibility approaching the signal
· Signage and striping compliance with the appropriate standards and practice
Figure 2.2 depicts the existing conditions and traffic controls documented during the field visit.
During the site visit, KOA field staff observed a few instances of problematic traffic behavior, such as:
· Speeding, identified both by observing speed feedback trailer readings as drivers passed by, and
visually clocking the arrival time of southbound vehicles approaching the signal upstream from the
curve;
· Red light running;
· Rapid brake maneuvering during the onset of the yellow/red interval; and
· High-speed southbound right turn movements from Hawthorne Boulevard onto Vallon Road (in
some instances while pedestrians were present in the crosswalk).
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Existing Condition and Data Collection
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The president of the La Cresta HOA provided KOA with several videos of the various traffic collisions that
occurred near the Hawthorne/Vallon intersection from October, 2020 to March, 2022 and KOA reviewed
videos up to date. La Cresta HOA indicated to KOA staff the following salient concerns:
· Numerous collisions at the intersection, including vehicle running off the road and into the
neighborhood walls at the northerly corners;
· Excessive speed (along the curve);
· Limited visibility at the curve;
· Distracted driving (texting, eating, talking, and the view); and
· Increased potential for loss of control in maneuvering the southbound right-turn
FIGURE 2.1 – ADT COUNT AND SPEED SURVEY LOCATIONS
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FIGURE 2.2 – EXISTING CONDITIONS AND TRAFFIC CONTROLS
`
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Existing Condition and Data Collection
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FIGURE 2.3 – EXISTING VERTICAL STREET PROFILES
Elevation Profile – Hawthorne Boulevard from Crest Road to Dupre Drive
Elevation Profile – Hawthorne Boulevard from Dupre Drive to Vallon Drive
Elevation Profile – Hawthorne Boulevard from Crestmont Lane to Via Rivera
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3.0 ANALYSIS
3.1 TRAFFIC VOLUMES
Average Daily Traffic (ADT) volumes were collected in the field to ascertain a baseline understanding of the
daily traffic volume levels on Hawthorne Boulevard, and at the signalized intersection at Hawthorne and
Vallon Drive. ADT volumes report the number of vehicles traversing a point on a roadway segment over a
24-hour period, and also indicate other information such as hourly traffic fluctuations throughout the day,
and the directional proportion of traffic flow. While ADT does not depict the exact origins and destinations
of those cars which it measures, it does reveal a sense of the daily “busyness” of a street as traveled by cars,
and may help to indicate the overall level of traffic regularly experienced on a given roadway segment.
The ADT counts on Hawthorne Boulevard were collected on two typical, consecutive weekdays in June 2021.
Figure 3.1 illustrates the 24-hour average daily traffic on Hawthorne Boulevard, reported for each direction
and for the two directions combined. Figure 3.2 shows the total roadway volumes during the AM hours
(i.e., midnight to noon), while Figure 3.3 shows the total roadway volumes for only the PM hours (noon to
midnight). The daily average traffic volume on Hawthorne Boulevard was approximately 13,900 vehicles per
day, including 14,625 vehicles per day (vpd) between Crest Road and Dupre Drive, 13,072 vpd between
Dupre Drive and Vallon Drive, and 13,942 vpd between Crestmont Lane and Via Rivera.
3.2 SPEED SURVEYS
Speed tube counters were deployed on Hawthorne Boulevard to measure the daily traffic speeds traveled
on each segment. Each speed survey was used to measure the prevailing 85th percentile speed traveled by
motorists throughout the day. The 85th percentile speed, or critical speed, represents the upper-speed limit
range that the greater majority of prudent motorists will drive. Speed survey locations were chosen based
on a review of the roadway conditions and selecting mid-block locations where the influence of traffic
controls and turning traffic would be minimized, in order to adequately represent free-flow travel speeds.
The regulatory speed limit on Hawthorne Boulevard is currently posted at 45 miles per hour. Existing curve
speed warning signs of 40 mph and 35 mph are also posted in the southbound direction, in advance of the
two horizontal curves between Crest Road and Vallon Drive. The two-way average (50th percentile) speed
recorded on Hawthorne Boulevard between Crest Road and Dupre Drive was within the speed limit, at 39
mph during the AM hours and 38 mph during the PM hours. The segments of Hawthorne Boulevard
between Dupre Drive and Vallon Drive, and between Vallon Drive and Via Rivera, also experienced a 50th
percentile speed within the speed limit, at 39 and 41 miles per hour, respectively, throughout the day.
An 85th percentile speed reported above the posted regulatory or advisory speed could indicate a potential
speeding concern, in which measures may be implemented to help reduce vehicle speeds. The two-day
average 85th percentile speeds recorded on southbound Hawthorne Boulevard in the vicinity of the La
Cresta neighborhood were all greater than the posted 45 mph speed limit. The 85th percentile speed on
southbound Hawthorne approaching Vallon, south of Dupre Drive, was 48 mph (3 mph in excess of the
speed limit). Tables 3.1, 3.2 & 3.3 summarize the two-day traffic speed data for the three study segments
on Hawthorne Boulevard.
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KOA also conducted a curve advisory speed (CAS) analysis based on the prevailing speed data, and the
geometric conditions of the roadway curve immediately north on Hawthorne Boulevard north of Vallon
Drive. Based on this analysis, it was determined that a curve advisory speed of 30 mph would be appropriate
to post to notify southbound motorists of the speed to traverse the curve on approach to the Vallon Drive
intersection, based on engineering guidance manuals.
FIGURE 3.1 – 24-HOUR AVERAGE DAILY TRAFFIC (ADT) VOLUMES
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FIGURE 3.2 – AM ONLY TRAFFIC VOLUMES (MIDNIGHT-NOON)
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FIGURE 3.3 – PM ONLY TRAFFIC VOLUMES (NOON-MIDNIGHT)
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TABLE 3.1 - SPEED SURVEY SUMMARY -
HAWTHORNE BOULEVARD BETWEEN DUPRE DRIVE & CREST ROAD
Segment: Hawthorne Boulevard between Dupre Drive and Crest Road
Survey Period Day 1- Tue (6/22/21) Day 2- Wed (6/23/21) 2-Day Average
Direction NB SB NB+SB NB SB NB+SB NB SB NB+SB
Percentile
Speed
15th 33 26 27 32 26 27 33 26 30
30 24 25 30 21 22 30 23 27
50th 43 35 39 43 35 39 43 35 39
42 35 39 41 33 37 42 34 38
85th
52 44 51 53 43 51 52 44 48
53 45 52 52 45 51 52 45 49
53 45 52 53 44 51 52 45 49
95th 56 48 56 57 47 56 57 48 53
57 48 57 57 48 56 57 48 53
Mean Speed
Average
42 35 39 42 34 39 42 35 39
43 34 38 41 33 37 42 34 38
10- MPH Pace 36-45 32-41 36-45 39-48 34-43 36-45 38-47 33-42 36-45
37-46 31-30 31-40 36-45 31-40 31-40 37-46 31-40 31-40
% in Pace 12% 13% 6% 11% 13% 6% 12% 13% 6%
7% 6% 3% 6% 6% 3% 7% 6% 3%
TABLE 3.2 - SPEED SURVEY SUMMARY –
HAWTHORNE BOULEVARD BETWEEN DUPRE DRIVE & VALLON DRIVE
Segment: Hawthorne Boulevard between Dupre Drive and Vallon Drive
Survey Period Day 1- Tue (6/22/21) Day 2- Wed (6/23/21) 2-Day Average
Direction NB SB NB+SB NB SB NB+SB NB SB NB+SB
Percentile
Speed
15th 32 29 28 30 29 28 31 29 28
32 28 27 31 28 28 32 28 28
50th 40 38 39 39 38 38 40 38 39
40 38 39 40 38 39 40 38 39
85th
48 46 49 48 46 47 48 46 48
49 47 50 49 48 50 49 48 50
49 47 50 49 48 49 49 47 49
95th 53 49 54 52 49 53 53 49 54
53 52 53 53 52 54 53 52 54
Mean Speed
Average
40 37 38 39 38 38 40 38 38
40 37 38 40 38 39 40 38 39
10- MPH Pace 36-45 34-43 36-45 36-45 36-45 36-45 36-45 35-44 36-45
34-43 31-40 36-45 33-42 31-40 34-43 34-43 31-40 35-46
% in Pace 13% 14% 7% 13% 13% 7% 13% 14% 7%
8% 6% 3% 8% 6% 3% 8% 6% 3%
Notes:
NB – Northbound ## AM period speed data (12AM-12PM) ## 24-hour speed
SB – Southbound ## PM period speed data (12PM-12AM) data (Daily)
Notes:
NB – Northbound ## AM period speed data (12AM-12PM) ## 24-hour speed
SB – Southbound ## PM period speed data (12PM-12AM) data (Daily)
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TABLE 3.3 - SPEED SURVEY SUMMARY –
HAWTHORNE BOULEVARD BETWEEN CRESTMONT LANE & VIA RIVERA
Segment: Hawthorne Boulevard between Crestmont Lane & Via Rivera
Survey Period Day 1- Tue (6/22/21) Day 2- Wed (6/23/21) 2-Day Average
Direction NB SB NB+SB NB SB NB+SB NB SB NB+SB
Percentile
Speed
15th 35 30 31 35 30 30 35 30 31
34 29 30 34 29 30 34 29 30
50th 43 39 41 44 39 41 44 39 41
44 39 42 44 39 41 44 39 42
85th
52 47 52 53 47 52 53 47 52
53 49 53 54 48 54 54 49 54
53 49 53 54 48 53 54 48 53
95th 55 51 55 57 50 57 56 51 56
57 53 58 59 53 59 58 53 59
Mean Speed
Average
43 39 41 44 38 41 44 39 41
44 39 42 44 39 42 44 39 42
10- MPH Pace 36-45 31-40 32-41 36-45 36-45 36-45 36-45 34-43 34-43
36-45 32-41 36-45 39-48 36-45 32-41 38-47 34-43 34-43
% in Pace 15% 12% 7% 14% 12% 6% 15% 12% 7%
6% 7% 3% 6% 6% 3% 6% 7% 3%
3.3 COLLISION ANALYSIS
Roadway Segment Collision History – KOA conducted a collision analysis for the subject roadway segment
on Hawthorne Boulevard north of Vallon Drive (to Dupre Drive), by comparing the latest available eight-
year collision history data with expected collision rates for similar roadway types. The analysis was based on
a review of reported mid-block traffic accident records provided by the City of Rancho Palos Verdes for a
9-year, 8-month and 24-day period spanning from January 2012 through September 2021. It should be
noted that only collisions documented and archived by law enforcement are reflected in the data; therefore,
unreported minor incidents and/or those not otherwise involving law enforcement officials were not
included. Figure 3.4a illustrates the collision diagram for subject roadway segment over the study period.
The calculated prevailing collision rate for the segment was computed by first determining the total number
of collisions (11) that occurred on the segment during the selected eight-year period, based on the initial
collision data provided from City records. The number of collisions in the February report was updated from
13 to 11, as the sphere of influence of the segment was re-evaluated and certain collisions were categorized
as occurring at adjacent intersections rather than on the mid-block segment. This value, along with the
measured daily traffic volume of the segment (13,072 vpd – see Figure 3.1) and the known segment length
(0.20 mi., adjusted from 0.38 mi. in the February report), was used in the standard formula below to
determine the calculated collision rate for the segment, expressed in terms of collisions per million vehicle
miles traveled:
Notes:
NB – Northbound ## AM period speed data (12AM-12PM) ## 24-hour speed
SB – Southbound ## PM period speed data (12PM-12AM) data (Daily)
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FIGURE 3.4A – COLLISION DIAGRAM: HAWTHORNE BOULEVARD BETWEEN DUPRE & VALLON
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Collision Rate (Collisions/MVM) = No. of Collisions x 1,000,000
ADT x Distance x No. of Days, where:
No. of Collisions Number of collisions on the segment during the selected analysis period, in both
directions:
· Historical analysis period: 11
· Recent 3-year period: 5
1,000,000 Conversion factor for Million-Vehicle-Miles (MVM)
ADT Average Daily Traffic (13,072 vehicles per day), in both directions
Distance Roadway segment distance traveled by each vehicle (0.20 miles)
No. of Days Number of days during the selected analysis period (days):
· Historical analysis period: 3,555 days
· Recent 3-year period: 1,095 days
It is important to note that due to the potential for regular lag in crash record reporting, the above-specified
analysis time period was adjusted to reflect the exact months of the documented traffic collisions, rather
than to apply a simple whole-year value. Furthermore, collisions located within the proximate influence area
of an adjacent signalized intersection were considered as occurring within those respective intersections,
and not within the mid-block roadway segment area.
Two separate roadway segment crash rates were calculated: (1) for the complete 9.74-year study period
covering the totality of the available data; and (2) for the recent 3-year period. The former crash rate reflects
the historical collision pattern of the segment, whereas the latter crash rate reflects a pattern of collisions
that is more recent. The resulting crash rate for the segment was calculated as 1.18 accidents per million
vehicle miles traveled across the subject segment, over the historical period. Similarly, the representative
crash rate for the segment over the most recent 3-year period for which data is available (i.e., 5 crashes over
1,095 days, from October 2018 through September 2021) is calculated as 1.75 accidents per million vehicle
miles traveled.
In order to evaluate the collision frequency of the street segment, the calculated collision rates were
compared to the average statewide collision rates for streets with comparable characteristics. The average
statewide collision rate for four-lane, divided highways of similar characteristics is 2.04 accidents per million
vehicle miles, per Caltrans’ Collision Data on California State Highways. Comparing these values, it was
determined that based on the reported historical accident data that the roadway segment on Hawthorne
Boulevard does not exhibit a higher-than-expected collision rate in comparison to statewide roadway
facilities with similar traffic and geometric characteristics.
Intersection Collisions – In order to identify potential crash patterns and opportunities for improvements,
KOA also examined the recent 9.74-year collision history for crashes occurring within the intersection of
Hawthorne Boulevard at Vallon Drive. Crash patterns were categorized by severity, collision type, Primary
Collision Factor (PCF), involved parties, lighting conditions, and damage involved (e.g., cars, concrete divider
wall, wall, curb, etc.). A total of 71 crashes was recorded within the overall study area between Dupre Drive
and Via Rivera during the historical analysis period, including:
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· 6 crashes within the intersection influence area of Hawthorne Boulevard and Dupre Drive;
· 11 crashes between the intersections of Hawthorne/Dupre and Hawthorne/Vallon (900-ft segment);
· 23 crashes within the intersection influence area of Hawthorne Boulevard and Vallon Drive; and
· 31 crashes between the intersections of Hawthorne/Vallon and Hawthorne/Via Rivera (4,400-ft
segment)
Figure 3.4b provides the collision diagram representing the past 9.74-year historical analysis period.
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FIGURE 3.4B – COLLISION DIAGRAM: HAWTHORNE BOULEVARD AT VALLON DRIVE
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· Most common crashes involved vehicles colliding with fixed roadside objects (11).
· 6 of the 23 collisions occurred on wet pavement conditions;
· 4 collisions involved southbound vehicles colliding with the center concrete divider, including 3 north
of Vallon Drive and 1 south of Vallon Drive;
· 2 collisions involved northbound vehicles colliding with roadside objects along the outside of the curve
· 1 southbound collisions occurred beween one bicycle crossing south on Vallon Drive struck by a right-
turning truck during the day
· 5 collisions involved eastbound vehicles struck broadside by southbound vehicles;
· Unsafe speeding and improper turning movements were cited as the most common primary collision
factors causing the incidents on Hawthorne Boulevard near Vallon Drive.
KOA calculated an estimated crash frequency for the intersection (reported in accidents per million
vehicles entering the intersection, or MVE), based on the ADT volumes recently collected on Hawthorne
Boulevard and an estimation of daily trips generated on Vallon Drive at the intersection with Hawthorne
Boulevard. Based on a single-family detached housing type land use, a daily traffic generation of 9.43 trips
per dwelling unit (per ITE Trip Generation, 11th edition), and approximately 150 single homes served by
the intersection at Vallon Drive and Hawthorne Boulevard, approximately 1,415 trips are estimated to
arrive at the signal from the side street approaches during the average daily period. Combined with the
average mid-segment, uni-directional ADT on Hawthorne Boulevard approaching Vallon Drive (14,105),
the total average daily traffic volume entering the intersection is 15,520 vehicles per day.
The calculated prevailing collision rate for the intersection was computed by first determining the total
number of collisions that occurred at the intersection during the period for which officially documented
crash evidence was available. This value, along with the estimated daily million entering vehicles at the
intersection, was used in the standard formula below to determine the calculated collision rate for the
intersection:
Collision Rate (Collisions/MEV) = No. of Collisions x 1,000,000
V x N x 365, where:
No. of Collisions Number of collisions at the intersection during the selected analysis period
· Historical analysis period: 23
· Recent 3-year period: 14
1,000,000 Conversion factor for Million-Entering-Vehicles (MEV)
V Traffic volumes entering the intersection daily (15,520 vpd)
N Number of years of data
· Historical analysis period: 9.74
· Recent 3-year period: 3
The estimated crash rate for the intersection was calculated as 0.417 accidents per million vehicles entering
the intersection, over the historical analysis period. The representative crash rate for the intersection over
the recent 3-year period was calculated as 0.824 accidents per million vehicles entering. If the most recent
pattern crash rate is expanded to March 2022 and the three crashes evidenced by the HOA are included,
the recent crash rate becomes 1.000 accidents per million vehicles entering the intersection.
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In order to evaluate the collision frequency of the intersection, the calculated collision rates were compared
to the average statewide collision rates for four-legged signalized intersections. The average statewide
collision rate for four-legged, signalized intersections in “suburban” areas is 0.420 accidents per million
entering vehicles, per Caltrans’ Collision Data on California State Highways. Comparing these values, it is
estimated that based on the reported historical accident data (9.74 years), the intersection of Hawthorne
Boulevard and Vallon Drive exhibits a lower-than-expected collision rate in comparison to statewide
signalized intersections. Considering only the recent 3-year period, the intersection experiences a higher-
than-expected collision rate in comparison to statewide signalized intersections.
It is important to note that collision rates for roadway segments are more readily used to identify collision
patterns along a given roadway facility, due to the increased likelihood of consistent, uniform and
comparable evaluation parameters such as number of lanes, roadway division type, terrain, design speed,
and facility type. Conversely, intersection facilities generally yield a more complex set of characteristics,
including variations in turning movement and lane configurations, traffic signal timing/phasing/detection
parameters, and pedestrian/bicyclist conflicts, which must be taken into consideration when comparing
intersection crash rates. Where the data is available, the most appropriate use of the intersection crash
rate is to determine the relative safety of an intersection when compared to similar intersections within
that specific jurisdiction.
Figure 3.4c illustrates the collision diagram for Hawthorne Boulevard and Vallon Drive which captures the
three (3) additional accidents recorded by the HOA and private-party video surveillance, which are not
currently available in the Los Angeles County Sheriff’s Department’s collision records.
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FIGURE 3.4C – COLLISION DIAGRAM: HAWTHORNE BLVD. AT VALLON DR. (ADDITIONAL DATA)
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3.4 SIGHT DISTANCE AND ANALYSIS
All roadway intersections have the potential for several different types of vehicular conflicts. The possibility
of these conflicts occurring can be greatly reduced through the provision of proper sight distances and
appropriate traffic controls. The avoidance of conflicts and the efficiency of traffic operations still depend
on the judgment, capabilities, and response of each driver. Ideally, the driver of a vehicle approaching an
intersection should have an unobstructed view of the entire intersection, including any traffic control
devices, and sufficient lengths along the intersecting street to permit the driver to anticipate and avoid
potential collisions. The sight distance needed under various assumptions of physical conditions and driver
behavior is directly related to vehicle speeds and to the resultant distances traversed during the perception-
reaction time and braking.
Specified areas along intersection approach legs and across their included corners should be clear of
obstructions that might block a drivers’ view of potentially conflicting vehicles. These “corner sight triangle”
areas are determined by calculating triangular geometries that account for observed driver behavior and
documented speed choices of drivers on the intersection approach. By providing unobstructed corner sight
areas, if a vehicle stopped on the minor street sees that the intersecting roadway is clear and leaves its
stopping point to either cross or enter into the major street, oncoming vehicles in either direction will have
sufficient time to negotiate the entering vehicle and prevent a collision.
The recommended geometry of the corner sight triangles, based on the American Association of State
Highway and Transportation Officials (AASHTO) A Policy on Geometric Design of Highways and Streets, 2011,
6th Edition, (Table 3.4) varies with the type of traffic control at the intersection and prevailing vehicle speeds.
It is important to note that these values are not required to be met as a uniform standard, and therefore
non-satisfaction of AASHTO sight distance recommendations does not necessarily indicate improper
roadway design. In reality, drivers will often self-mitigate low sight distance conditions by encroaching
slightly beyond the stop line before entering the intersecting roadway to gain a better view of oncoming
traffic. However, it is strongly recommended that as a conservative measure, intersections account for the
AASHTO minimum sight distance on a case-by-case basis to minimize the potential for adverse vehicle
conflicts.
For left turns from the minor street, the minimum recommended sight distance based on the AASHTO
method is 500 feet, measured along the major street (for a 45 mph facility), between the approaching and
stopped vehicles. For right-turn movements, the minimum recommended sight distance is 430 feet. Since
the intersection of Vallon Drive and Hawthorne Boulevard is presently signalized, a dedicated time interval
to allow right-of-way for vehicles on Vallon Drive to proceed onto Hawthorne Boulevard unimpeded is
already provided. Through- and left-turn movements from Vallon Drive are not allowed to proceed until a
green signal phase is given. This section therefore only focuses on right-turning vehicles, since right turns
may be performed on the red signal phase once a vehicle is already stopped and is prepared to make a
decision to safely turn.
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TABLE 3.4 – MINIMUM RECOMMENDED SIGHT DISTANCE BASED ON VEHICLE MANEUVER
For vehicles stopped at the limit line on Vallon Drive, wishing to turn right onto southbound Hawthorne
Boulevard, the measured sight distance to southbound approaching traffic on Hawthorne Boulevard in the
adjacent Number 2 lane was determined to be approximately 104 feet, which does not satisfy the
recommended minimum intersection sight distance of 430 feet. Alternatively, where stopped vehicles on
Vallon Drive wishing to turn right (southbound) proceed slightly into the intersection in order to increase
their line of sight of oncoming traffic, the sight distance was improved to 441 feet, which does meet the
recommended minimum intersection sight distance of 430 feet.
A variety of conditions can exist on a signalized intersection approach which may warrant the need for a No
Turn on Red sign. This could include, for example:
· Where the sight distance to vehicles approaching from the left is inadequate;
· Where the geometrics or operational characteristics of the intersection result in unexpected conflicts;
During the activation of an exclusive pedestrian phase;
· Where an unacceptable number of pedestrian conflicts with right-turn-on-red maneuvers, especially
involving children, older pedestrians, or persons with disabilities, have occurred; and/or
· Where the skew angle of the intersecting roadways creates difficulty for drivers to see traffic
approaching from their left.
According to the sight distance analysis, the left-hand sight distance for motorists on Vallon Drive stopped
behind the limit line does not meet the recommended minimum for right-turn-on-red movements with the
potential to conflict with oncoming southbound traffic on Hawthorne Boulevard. However, based on the
typical scenario in which vehicles wishing to turn right on the red indication would proceed slowly and
cautiously into the intersection in order to increase their sight lines, adequate sight is provided (see Figure
3.5). California case law has ruled that the practice of stopping at a limit line and then "creeping" forward
to a point of visibility has long been recognized as "practical" under California Law.1
In view of the absence of right-turn-on-red collisions, and the observed available opportunity for drivers to
1 Per California Case Law, "the driver of an approaching car about to enter a through highway [e.g., to proceed through or turn]
must stop in accordance with Section 577, Vehicle Code to observe traffic conditions; but if the point where he stopped is distant
from the actual crossing of the travel lanes he may move up to that point carefully if he can do so without danger and decide there
whether he can enter or cross the through highway without any car then moving on the through highway causing an immediate
danger.” Source(s): Hefner v. County of Sacramento, 1988; Smith v. Pellissier, 1955, 134 Cal. App. 2d 562, 570 [286 P.2d 66]); Elmore v.
County of Lassen, 10 Cal.App.2d 229, 232, 51 P.2d 481
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freely attain for themselves adequate sight distance, it may be presumed that the typical reasonable and
prudent driver would not attempt to turn right on the red signal phase when positioned behind the
crosswalk/limit line where the sight distance is constrained. Therefore, a “No Right Turn On Red” sign is not
recommended at this time, and eastbound motorists turning right from Vallon Drive onto Hawthorne
Boulevard should be afforded the continued opportunity to exercise their good driving judgment in
attempting right turns during the red signal phase, from a position that allows for adequate sight distance.
Figure 3.5 illustrates the available versus recommended minimum sight distance for each of the above
stated scenarios.
Adequate stopping sight distance (SSD) should be provided for motorists approaching southbound along
the curve on Hawthorne Boulevard, both to view potential vehicles stopped in the road and to view the
downstream traffic signal at Vallon Drive. Based on a 45 mph design speed and 9% downgrade, the
recommended stopping sight distance for the inside (#2) southbound travel lane is 427 feet. The existing
available SSD is 530’, measured along the centerline of the inside southbound lane between the driver’s
position and the limit line; therefore, adequate stopping sight distance to view the approaching traffic signal
is provided. A representative visual approximation of the existing available SSD for vehicles in the
southbound #2 lane and the traffic signal is shown below:
Existing Stopping Sight Distance (SSD) for Southbound Inside Travel Lane (45 mph approach speed)
Left – Maximum available SSD (530 ft.); Right – Minimum recommended SSD (427 ft.)
Sufficient SSD across the inside of horizontal curves—i.e., the minimum chord length of the curve where
sight lines between vehicles along the same travel path are not obstructed—should also be provided. In
such cases where there are sight obstructions, such as walls, cut slopes, building structures, and/or
longitudinal barriers, on the inside of the curve and their removal to increase sight distance is impractical,
other roadway design factors may be modified may be made to accommodate the existing available SSD.
Along the existing curve, there is a boundary wall set back approximately 8 feet from the right-hand curb
line, resulting in a horizontal sight-line offset (HSO) of 19 feet. The existing radius of the inside lane travel
path is approximately 493 feet. Considering these two fixed constraints together, the available SSD for the
#2 lane is 270 feet. For a 45 mph travel speed under the existing geometric and physical constraints, the
recommended minimum SSD is 325 feet.
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Analysis
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FIGURE 3.5 – SIGHT DISTANCE ANALYSIS FOR VALLON DRIVE RIGHT TURNS ONTO
SOUTHBOUND HAWTHORNE BOULEVARD
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Analysis
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Since the minimum SSD cannot be provided under the above-stated conditions, one or more of the existing
roadway/traffic design factors should be modified to increase the minimum available sight distance. Due to
the relative infeasibility of relocating the boundary wall back to increase the HSO, increasing the horizontal
radius or reducing the vertical grade, it is recommended that the travel speed along the curve be reduced
in order to reduce the minimum SSD along the curve. A travel speed of 35 mph on a 9% downgrade yields
a recommended stopping sight distance of 287 feet, while a travel speed of 30 mph on a 9% downgrade
yields a recommended stopping sight distance of 227 feet. In order to satisfy the existing minimum SSD
along the curve, it is therefore recommended that the curve advisory speed be reduced from 35 mph to 30
mph. Figure 3.6 illustrates the existing stopping sight distance on the curve/downgrade along the inside
(#2) travel lane.
FIGURE 3.6 – EXISTING AVAILABLE STOPPING SIGHT DISTANCE FOR
SOUTHBOUND HAWTHORNE BOULEVARD ALONG THE CURVE (INSIDE LANE; 45 MPH)
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Analysis
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KOA investigated the HOA’s suggestion of timing the Hawthorne/Vallon traffic signal to coordinate with
the upstream traffic signal at Hawthorne/Dupre (Ryan Park northerly entrance). The suggested action
involved coordinating all southbound phases (i.e., SB Through, WB Left) at the Dupre/Ryan traffic signal to
revert to red phase as vehicles exiting La Cresta arrive at the Hawthorne/Vallon signal and send a call for a
green phase to proceed left or through. This green phase would subsequently be given to Vallon traffic only
after all of the residual traffic that cleared the upstream red signal phase at Dupre/Ryan has also cleared
the Vallon traffic signal on green. Southbound-through and westbound-left vehicles waiting on red at the
Ryan Park traffic signal to proceed southbound onto Hawthorne Boulevard would then be released, in
sequence, only once the Vallon Drive signal phase has been terminated and intersection traffic is completely
clear.
The HOA’s suggested traffic signal coordination and timing measures were considered; however, KOA does
not recommend moving forward with this suggestion. Presumably, the intent of the suggested measure is
to ensure that southbound traffic approaching Vallon Drive not be given the opportunity to decide on to
stop on red. Rather, all southbound traffic approaching Vallon would be assigned a green signal indication,
and revert to red only once (1) the Dupre/Ryan Park signal has stopped southbound traffic upstream, and
(2) residual southbound traffic has completely cleared the Vallon signal.
While the suggestion to modify the signal timing in this manner does attempt serve to address the problem
of red-light running at the Vallon signal by removing the decision to stop at the red light, it would likely
elevate the potential for new and additional traffic safety issues to arise at the Dupre/Ryan Park signal. The
reasons for this concern are as follows:
· A “false call” would need to be programmed at the Dupre/Ryan Park signal, to hold westbound-left
and southbound-through traffic on red for an extended period of time, perhaps an additional minute
or longer, which could increase the likelihood of adverse driver behavior at Dupre/Ryan Park.
· The additional all-red time would need to be programmed to include, for example, an additional 30+
seconds for southbound residual traffic to clear the downstream Vallon signal, +10 seconds for
southbound/northbound lefts, and +10 seconds for Vallon traffic (up to 17 or 27 seconds when
pedestrians are crossing Vallon or Hawthorne, respectively).
· Potential adverse effects of the false call programming include:
o Increased driver frustration due to waiting for no evident conflicting traffic (since the
downstream traffic signal at Vallon is not visible from the park entrance);
o A subsequent increase in unsafe speeding by motorists who were held at the Dupre/Ryan
Park signal, in order to make up for perceived lost time.
o A likely increase in the rate of red-light violations from either or both westbound-
left/southbound-through traffic in order to attempt to clear the Dupre/Ryan Park signal
In conclusion, the two subject signalized intersections are generally considered as spaced too far apart
(approximately 2,000 feet) for the suggested traffic signal operation to be achieved effectively, and may
result in an increased rate of other unsafe driving patterns and traffic violations. While this
timing/coordination measure intends to eliminate the need to counter distracted driving and red light
running occurrences, there are other feasible strategies and traffic calming measures that are available
which may be applied and implemented at a more reasonable cost, with fewer opportunities for new issues
to arise as a result. The following section provides a series of near-, medium- and long-term
recommendations that address the various problematic driver behaviors at the Hawthorne/Vallon signal.
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4.0 RECOMMENDATIONS
4.1 RECOMMENDED TRAFFIC CALMING MEASURES
Field observations, average daily traffic (ADT) volume data, speed surveys and collision data all contribute
towards a need for traffic calming recommendations. In conjunction with the measured traffic data and
input from the La Cresta HOA and its residents, KOA identified and confirmed the need to address traffic
issues on Hawthorne Boulevard in the vicinity of Vallon Drive.
The following traffic calming countermeasures were developed to address the concerns described above,
including: prevailing traffic speeds above the posted speed limit, recent crash activity at the intersection of
Hawthorne Boulevard and Vallon Drive, sight distance issues, and reported distracted driving behaviors.
Discretion should be employed by the City in coordination with the La Cresta community to strategize the
following recommendations on an appropriate timeframe, as some measures can be implemented fairly
quickly and at a low cost, while others would require a larger degree of funding, community support and/or
design effort. Each of the recommended traffic calming improvements described below are depicted on the
attached Conceptual Plan exhibit.
Short-Term Improvements
· Countermeasure #1: Install 3” yellow retroreflective backplate border strips on all signal indications at
Vallon Drive to enhance the long-distance visibility and overall conspicuity of the traffic signal heads.
· Countermeasure #2: Install yellow retroreflective concrete barrier-mounted delineators.
· Countermeasure #3: Update the existing curve advisory speed signage and pavement markings –
Remove the existing signs and markings and replace with the signage/striping configurations shown
on the attached exhibit, including revised chevron/right arrow placard spaced at 80’ intervals along
the center median barrier.
· Countermeasure #4: Install high-visibility white thermoplastic ladder crosswalk pavement markings
within the existing marked crosswalk on the south, west and east legs of the intersection on Vallon to
better draw the attention of turning motorists to pedestrians in the crosswalk and at the intersection
corners.
· Countermeasure #5: Install “Right Turning Vehicles Yield to Peds” signage on the southbound near-
and far-side signal poles at the Hawthorne/Vallon intersection.
o Additional Notes: Based on ITE Trip Generation 11th Edition trip rates for typical
residential/detached dwelling units, approximately 68 vehicle trips during the average
weekday PM peak hour are expected to be generated in the inbound direction, from
Hawthorne Boulevard onto Vallon Drive. Assuming a 70/30 split (based on existing turn
pocket lengths) for the southbound and northbound directions, respectively, it is estimated
that approximately 48 of these vehicles, or 2 vehicles per average two-minute signal cycle,
would access the southbound right-turn pocket to turn into the La Cresta community during
a typical weekday evening peak hour. The existing right-turn pocket capacity can
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accommodate approximately 9 vehicles in simultaneous storage; therefore, during the
average signal cycle the existing right-turn pocket should be sufficient to serve weekday PM
peak hour volumes, and no further extension of the existing right-turn lane would be justified.
· Countermeasure #6: Relocate the existing “Right Lane Must Turn Right” sign to the beginning of the
right-turn pocket per standard practice.
· Countermeasure #7: Install yellow centerline extension line across the median break in front of the
southerly driveway at Ryan Park.
· Countermeasure #8: Refresh the existing “SIGNAL AHEAD” pavement markings with retroreflective
thermoplastic.
· Countermeasure #9: Continue to deploy the existing speed feedback trailer in the southbound
direction on Hawthorne Boulevard in advance of the horizontal curve north of Vallon Drive.
o Coordinate with Public Works and law enforcement to identify an appropriate location for a
permanent, pole-mounted/solar-powered speed feedback signs upstream from the
horizontal curve approaching Vallon Drive.
Medium-Term Improvements
· Countermeasure #10: Narrow the southbound #2 travel lane to 11 feet wide to reduce errant
maneuvers in the curb lane along the horizontal curve
o Install an 8’ wide striped shoulder with a 6” edge line and 8-inch, 45-degree chevron/hatch
markings spaced at 40-foot intervals.
· Countermeasure #11: Traffic Signal Timing Modifications
o Recut the existing advance detection loops (Existing 225’) and place further upstream (300’)
to accommodate a 45mph approach speed. This measure will improve the ability for the traffic
signal controller at Hawthorne Boulevard and Vallon Drive to appropriately allocate green
time extensions and yellow/red change intervals to southbound traffic based on the posted
speed limit.
· Countermeasure #12: Update existing traffic signal timing plans
o The existing yellow interval for through movements on Hawthorne Boulevard is 4.5 seconds.
It is recommended that the yellow time be updated to 4.8 seconds (i.e., Phases 2 and 6), per
Table 4D-102 (CA) of the 2014 CA MUTCD Rev 6 minimum guidelines for a 45 mph posted
speed. This measure will provide a fraction of a second increase to the yellow change interval
for southbound approaching vehicles. Particularly for drivers who traverse this intersection on
a regular basis, the adjustment may help to reduce driver’s indecision on whether to stop or
proceed through the intersection on the yellow light change, which can reduce the potential
for rear-end accidents and/or unsafe speeding.
o Maintain the 1.0 red clearance interval. Based on the gathered traffic data and video
information, it is not readily apparent that the southbound vehicles running the red light
involve those motorists who are “hurrying” to catch the end of the yellow interval. Therefore,
extending the red clearance is not anticipated to yield a desired safety benefit and should be
maintained as-is on the existing signal timing charts.
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· Countermeasure #13: Traffic Signal Hardware Modifications
o Add a pedestrian signal (e.g., countdown heads and ADA-compliant pushbuttons) across the
east leg of the intersection on Vallon Drive. There is an existing marked crosswalk and
connecting curb ramps; however, there are currently no existing pedestrian signals.
· Countermeasure #14: Install transverse rumble strips across the travel lanes on Hawthorne Boulevard
in the southbound direction to increase driver attention to the changing roadway conditions along
the curve.
o Option 1: Procure and install temporary, modular rumble strip systems to gauge their
effectiveness and overall community acceptance of the devices before any permanent
installation is considered. Particularly for high-speed and/or high-volume streets abutting
residential areas, the 24-hour noise generated by vehicles traversing the rumble strips is a
common concern of residents in close proximity to the installations.
Source: 2018 Caltrans Standard Plan
o Option 2: Install “rumble stripes”, i.e., milled rumble strips which run longitudinally (alongside,
and not across the travel lanes – see top left image below) and concurrent with the edge line
striping to provide audible/vibrational indication to motorists who begin to leave the traveled
way. They may also be combined with lane line and edgeline optical speed markings to further
bring awareness to drivers to slow down for an unexpected roadway condition ahead (see
right-hand image on the following page).
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Long-term Improvements
· Countermeasure #15: Traffic Signal Modifications
o Add a nearside 3-section signal indication in the southbound direction on Hawthorne
Boulevard approaching Vallon Drive. The existing 1-A pole at the northwest corner should be
replaced with a new Type 15TS signal to accommodate the additional signal head, as well as
added overhead lighting to improve intersection/corner visibility at night.
o Replace the existing traffic signal standard pole and mast arm at the southwest corner (facing
southbound traffic) with a new pole to accommodate an additional mast arm-mounted traffic
signal head (for a total of 2 overhead signals for the through lanes). Position the left-turn
signal indication more directly in-line with the existing southbound left-turn lane.
· Countermeasure #16: Install a “Signal Ahead” Warning System, to replace the existing advisory
signage.
o Install an overhead flashing warning beacon system, complete with “SIGNAL AHEAD” signage
and two, 12-inch overhead yellow signal faces.
“Signal Ahead” Warning System with pole-mounted and overhead flashing yellow beacons
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· Countermeasure #17: Install Street Lighting
o Install street lights along the roadside in the northbound direction, to improve visibility of the
outer edge of the horizontal curve and help with minimizing run-off-road collisions. As shown
in the Concept Exhibit, at a minimum the street lights should be installed between 400’ and
800’ north of Vallon Drive to address the historical collision patterns, and located outside of
overrun area of northbound motorists. An optional consideration could include glare shields
to minimize the impact of lighting on adjacent residents.
4.2 IMPLEMENTATION
The countermeasures described in the previous section are bundled into three distinct categories: Short-Term,
Medium-Term and Long-Term. Implementation of the recommended traffic calming measures may be rolled
out using an incremental approach, beginning with measures that are implementable on a relatively short time
frame using City forces and traffic control devices and materials currently available. Traffic conditions and
driving patterns should be monitored upon completion of the short-term improvements, including collection
of traffic speed data and visual observations in the field during critical commuter times of the day.
Should the cumulative effect of the short-term measures not sufficiently lower traffic speeds and/or observed
problematic driving behaviors, it is recommended that the City consider pursuing the
construction/implementation of the recommended medium-term improvements. Similarly, upon installation
of the medium-term countermeasures, the resulting impact on traffic patterns should once again be measured
and evaluated to determine the extent to which the reported speeding, sight distance and distracted driving
patterns are alleviated. Finally, the recommended long-term countermeasures may be considered where the
cumulative benefits of the short- and medium-term measures are determined to be ineffective in addressing
the traffic concerns of the community and the City.
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