HomeMy WebLinkAboutProposed Roundabout Design Concept - San Pablo Corridor Imprvmnts 619-16 STAFF REPORT
CITY OF PALM DESERT
PUBLIC WORKS DEPARTMENT
MEETING DATE: May 10, 2018
PREPARED BY: Joel Montalvo, P.E., Senior Engineer
REQUEST: Authorize the proposed roundabout design concept for the
intersection of San Pablo and San Gorgonio Way and San Pablo
Avenue and the College of the Desert's east entrance as part of the
San Pablo Corridor improvements. (Project No. 691-16).
Recommendation
By Minute Motion:
1. Authorize staff to proceed with the proposed roundabout design concept
for the intersection of San Pablo and San Gorgonio Way and San Pablo
Avenue and the College of the Desert's east entrance as part of the San
Pablo Corridor improvements. (Project No. 691-16).
Strategic Plan
The improvements to the Corridor fulfill priorities identified in the City's Strategic Plan,
including the following:
• Land Use - Priority 4: "Create a mixed-use city core integrating shopping, dining,
lodging, and housing."
• Tourism and Marketing — Priority 1: "Improve access to Palm Desert and its
attractions to enhance the ease of lifestyle."
• Transportation—Priority 1: "Create walkable neighborhoods and areas within Palm
Desert that would include residential, retail, services and employment centers, and
parks, recreation and open space to reduce the use of low occupancy vehicles."
• Transportation — Priority 3: `De-emphasize single/low-occupancy vehicles and
optimize modes of travel (bus, carpool, golf-cart, bicycle and pedestrian)."
Background Analysis
On July 13, 2017, the City Council approved the preliminary design for the San Pablo
Avenue Corridor improvements project prepared by Sargent Town Planning. The plan
represented the collective efforts of the San Pablo team, and was vetted with the City
Manager, the Director of Public Works, and the Director of Community Development. The
May 10, 2108 - Staff Report
San Pablo Avenue Roundabouts
Page 2 of 3
City Council also directed staff to prepare final construction drawings based on the
Concept.
On March 22, 2018, the City Council awarded the design contract to Dokken Engineering
for the San Pablo Corridor Improvements. At the same Council meeting, Council
members voiced their concerns about the use of roundabouts at two intersections within
the San Pablo Corridor. Specifically, Council members were concerned about the
prioritization of vehicles rather than pedestrians and bicycles at the intersection of San
Pablo Avenue and San Gorgonio Way. Council members were also concerned about the
proposed roundabout at the intersection of the San Pablo Avenue and the east entrance
to the College of the Desert campus. The City Manager asked staff to research the
Council's concerns and present the findings at the next study session.
Discussion
As requested, staff and Dokken Engineering researched the use of roundabouts at
intersections, and the design features that can be added to roundabouts to protect
pedestrians and cyclists. Dokken engineering presented a position paper that was
distributed to the City Council. The position paper highlighted the reduction in
pedestrian, bicycle, and vehicle collisions at appropriately designed roundabouts. The
position paper also presented data from the Federal Highway Administration (FHWA)
demonstrating that roundabouts reduce conflicts and improve the safety for all users.
On April 26, 2018, Dokken engineering presented to the City Council information that
further analyzed and discussed roundabout safety. The Dokken team used many
examples of roundabouts and the potential features that can be incorporated in the
design to produce a safe and usable intersection for all.
Staff has reviewed all of the data presented and believes roundabouts are a safe and
viable alternative for the two intersections, and recommends that they be utilized for the
final design.
May 10, 2108 - Staff Report
San Pablo Avenue Roundabouts
Page 3 of 3
Fiscal Analysis
This action has no immediate fiscal impact. However, the removal of one or two
roundabouts might lower the overall construction cost of the project. Change to the
fundamental design concept after this point will incur additional contract costs.
LEGAL REVIEW DEPT. REVIEW FINANCIAL CITY
REVIEW MANAGER
N/A
Robert W. Hargrea s imothy R Jo son, P.E. ar'et Moore Lauri Aylaian
City Attorney Independent In erim Director Director of Finance City Manager
of Public Works
CONSULTANT: Dokken Engineering, Inc.
1450 Frazee Road, Suite 100
San Diego, California 92108
ATTACHMENTS: Position Paper
Vicinity Map
X1DGKKEN ENGINEERING
Transportation Solutions from Concept to Construction
POSITION PAPER
For: City of Palm Desert
Attention: Project Manager;Joel Montalvo, PE
From: Project Engineer; Michael Greer, PE,TE
Subject: Safety of Pedestrians and Cyclists at Crosswalks Located at
Roundabouts and Stop-Controlled Intersections
Date: April 17,2018
Mr. Montalvo,
Dokken Engineering has prepared the following position paper to present professional
opinions and facts related to the safety of pedestrians and bicyclists crossing streets with
various intersection controls for the City of Palm Desert's San Pablo Avenue Corridor
Improvements Project (City's Project). Specifically, this position paper will elaborate on the
safety benefits of roundabouts as compared to stop-controlled intersections with standard and
other crosswalk designs, including the "Barnes' Dance" style crosswalk (named after engineer
Henry Barnes) which allows pedestrians and cyclists to cross in all directions simultaneously
while vehicles are stopped by traffic control devices.
For the City's Project, there are two existing stop-controlled intersections that are being
further evaluated in this position paper to illustrate the benefits of moving forward with
roundabout designs. The first location is at the intersection of San Pablo Avenue with San
Gorgonio Way, which will act as a transition between Zone 1 and Zone 2 of the City's
Project. The second location is at the intersection of San Pablo Avenue with City Hall and
College of the Desert driveways, which will provide future connectivity to the Coachella
Valley Link (CV-Link) Hub and the future roundabout at Magnesia Falls Drive to the north.
With the conversion of Zone 1 to a destination where large public events can be held within a
new plaza and the activity surrounding the Civic Center and College of the Desert campus,
both intersection locations can expect to see a high amount of pedestrian activity and
crossings during peak periods. Additionally, cyclist and small electric vehicle (golf cart)
activity is expected to increase at both locations with the addition of the future CV-Link Hub
and the overall conversion of the corridor. The roadway must convey clear messages and
paths of travel for maximum driver-pedestrian-cyclist awareness and communication.
Before highlighting new research related to the safety benefits specific to pedestrians and
cyclists at roundabouts we'd like to provide further background on research done by City staff
to date. In May 2016, the City hosted "Vision San Pablo" an event that demonstrated and
presented the proposed road-diet to the community. More than 2,000 people attended the
event with 130 people providing surveys. Of those surveyed, 83% voiced support for
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Page 2 April 17, 2018
roundabouts and more than 95% voiced support for the envisioned permanent street
improvements. One consistent comment was presented by the community, "slow vehicle
traffic" through this area. Staff has also heard that drivers tend to "run" through the existing
stop signs at San Pablo Avenue and San Gorgonio Way. The community and staff supports
the use of a roundabout at this intersection to slow traffic and to prohibit vehicles from
running through stop signs. Staff would also note that the roundabout was demonstrated
during the "Vision San Pablo" event and that no vehicle collisions or pedestrian safety
conflicts were present.
Research, Figures and Ouotes
The following is a quote from the Federal Highway Administration's (FHWA's) website:
ht tp s://safety.fh w a.dot.go vlintersection/i n novat i velrou ndabou t sl
The FHWA Office of Safety...Roundabouts are designed to improve safety for all users,
including pedestrians and bicycles.
By reducing the number and severity of conflict points, and because of the lower speeds of
vehicles moving through the intersection, roundabouts are a significantly safer type of
intersection. The diagram below excerpted from Roundabouts: An Informational Guide,
Second Edition (published as NCHRP Report 672) illustrates the difference in conflict
points between a conventional, four-legged intersection and an equivalent single lane
roundabout. There are 32 conflict points associated with a conventional intersection — 8
merging (or joining), 8 diverging (or separating) and 16 crossing. In contrast, there are
only 8 total conflict points at an equivalent roundabout—4 merging and 4 diverging. Not
only are conflict points halved with the roundabout, the type of conflicts that remain are
the same-direction variety, which result in substantially less severity, and as a result, less
likelihood of injury. The reduction of both the total number of conflict points and their
severity is also true for pedestrians, also shown below in diagrams excerpted from the
Guide.
■�
Pedestrian-Vehicle Conflict Paint Comparison
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• Right turn on green conflict
• Red light running conflict
• Left turn on green conflict p vehicle/pedestrian Co-rlicts
o Red light running or right turn on red conflict Source NCHRP Report 672 Exhibits 5-7 and 5 8
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Page 3 April 17, 2018
The FHWA has also produced a ten-minute video titled Modern Roundabouts:A Safer Choice
(https://youtu.beluhHzly 61WM) which gives an overview of some of the benefits of modern
roundabouts. Beginning at minute seven of the video, there is an explanation of the benefits
specific to pedestrians and bicyclists. This is a quote from the video:
In general, pedestrians face far less risk at roundabouts than traditional intersections,
primarily because of the slower speeds and the elimination of turns across the pedestrian
crosswalks. Splitter islands both shorten the crossing distance for pedestrians and allow
them to cross one direction of traffic at a time. All of this adds up to increased safety.
By reducing vehicle speeds on the approach to a roundabout the safety of pedestrians is
increased as drivers have a greater chance of stopping while in the process of slowing.
Statistics show that a pedestrian involved in a collision with a vehicle going 20mph has an
85% chance of survival, while that chance of survival is reduced to just 15% when that same
vehicle is traveling 40mph. On the approach to an intersection a driver is faced with multiple
decision points and roundabouts separate the point where a pedestrian might cross the road
from the point where the vehicle will enter the roundabout, thereby allowing the driver to
make one decision at a time. Reduction in collisions
This is accomplished by placing
crosswalks far enough in front of ""'
yield line to ensure the driver's
attention is solely focused on the go%1111
pedestrian crossing. Once the K.l reciuclion
driver decides it is safe to
proceed based on lack of reduc on
pedestrian activity, they continue
toward the entry of the
roundabout. The next decision a
, 111 driver faces is when to enter the
roundabout based only on the ao%
conflicting vehicles. This figure rcduCtiOn
to the right from the FHWA and
Insurance Institute for Highway p'
Safety (IIHS) illustrates the
percent reduction in collisions
that roundabouts are typically
141117 able to achieve. The reduction I Fifthly Pedestrian
ns
of speeds on the approach to the Sc"= Fyd°','"91°"Y4-1r4r.ralcr and oGurancA . 'Ott..Fig uy, ,;cy-,.wa, ors,
intersection is done across a greater distance with roundabouts as opposed to stop-controlled
intersections due to proper design of splitter islands and the ever-present center island of the
roundabout which signifies to drivers from a much greater distance that they are approaching
an intersection with potential turn movements and crossing activity.
The following is a quote that describes a few reasons "why roundabouts help reduce the
likelihood and severity of collisions" from the Washington Department of Transportation
(WSDOT)website: https://www.wsdot.wa.govlSafety/roundaboutsfbenefits.htm
"There are several reasons why roundabouts help reduce the likelihood and severity of
collisions:
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Page 4 April 17, 2018
• Low travel speeds— Drivers must slow down and yield to traffic before entering a
roundabout. Speeds in the roundabout are typically between 15 and 20 miles per hour.
The few collisions that occur in roundabouts are typically minor and cause few
injuries since they occur at such low speeds.
• No light to beat—Roundabouts are designed to promote a continuous, circular flow of
traffic. Drivers need only yield to traffic before entering a roundabout; if there is no
traffic in the roundabout, drivers are not required to stop. Because traffic is
constantly flowing through the intersection, drivers don't have the incentive to speed
up to try and "beat the light,"like they might at a traditional intersection.
• One-way travel—Roads entering a roundabout are gently curved to direct drivers into
the intersection and help them travel counterclockwise around the roundabout. The
curved roads and one-way travel around the roundabout eliminate the possibility for
T-bone and head-on collisions."
The following is a quote that describes another reason for increased pedestrian safety at
roundabouts related to the crossing distances and patterns from the IIHS and Highway Loss
Data Institute (HLDI) website: http://www.iihs.org/iihs/topics/t/roundabouts/qanda
"8. Are roundabouts safe for pedestrians?
Roundabouts generally are safer for pedestrians than traditional intersections. In a
roundabout, pedestrians walk on sidewalks around the perimeter of the circular roadway.
If they need to cross the roadway, they cross only one direction of traffic at a time. In
addition, crossing distances are relatively short, and traffic speeds are lower than at
traditional intersections.
Studies in Europe indicate that, on average, converting conventional intersections to
roundabouts can reduce pedestrian crashes by about 75 percent."
Crossing distances across crosswalks at roundabouts are typically about half the length of
those at typical stop-controlled intersections due to the pedestrian refuge area provided within
splitter islands. This is also the feature that allows pedestrians to focus on vehicles coming
from one direction at a time as opposed to needing to keep their head on a swivel as they walk
across longer crosswalks without refuge areas. As an example, the existing crossing distance
for the crosswalk across the northerly leg of the stop-controlled intersection at San Gorgonio
Way and San Pablo Avenue is ninety feet (90') which would be reduced to two twenty-foot
(2-20ft) crossings with a roundabout and splitter island design as identified in the picture
below.
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Page 5 April 17, 2018
Examples of roundabouts with high pedestrian volumes that have been implemented
successfully include two recently constructed roundabouts along Route 28 at Bear Street and
Coon Street in Kings Beach, North Lake Tahoe in Placer County, CA and five roundabouts
constructed along La Jolla Boulevard in the Bird Rock Beach Community, San Diego County,
CA.
Lastly, we'll elaborate on the "Barnes' Dance" crosswalk treatment, also known as the
pedestrian scramble, which is an intersection where vehicle traffic stops while pedestrians
cross in all directions — including diagonally. While he didn't invent the concept, Henry
Barnes popularized the use of this type of crosswalk treatment while serving as the
transportation commissioner of Denver in the 1950's and later New York City in the 1960's.
Typically, this type of crosswalk treatment has been installed at signalized intersections and
the all-pedestrian phase is given a block of time within the overall signal cycle, thus reducing
potential conflicts between vehicles and pedestrians. This type of crosswalk treatment can be
implemented at existing signalized intersections, such as San Pablo Avenue with Highway
111. However, this also results in either longer wait times for both drivers and pedestrians, or
shorter traffic-signal phases where less traffic could flow through an intersection in a single
cycle. Use of this type of crosswalk at an existing stop-controlled intersection is rare and
should be carefully considered for the impacts to vehicle driver delay as pedestrians will be
allowed to cross always. To move forward with Vision Zero, the City of Los Angeles
implemented their first four-way-stop scramble crossing at the intersection of Sylvan Street
and Sylmar Avenue in the community of Van Nuys in August 2017, adjacent to the Van Nuys
Civic Child Development Center.
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Page 6 April 17, 2018
References
Brilon,W.; Stuwe, B.; and Drews, O. 1993. Sicherheit and Leistungsfahigkeit von
Kreisverkehrsplatzen (Safety and capacity of roundabouts). FE Nr 77359/91. Bochum,
Germany: Lehrstuhl fur Verkehrswesen, Ruhr-Universitat Bochum. Cited by: Elvik R.
Effects on road safety of converting intersections to roundabouts: a review of evidence
from non-US studies. Transportation Research Record 1847:1-10.
Brude, U. and Larsson, J. 2000. What roundabout design provides the highest possible
safety?Nordic Road&Transport Research 2000(2):17-21.
Hourdos, J.; Richfield, V.; and Shauer, M. 2012. Investigation of pedestrian/bicyclist risk in
Minnesota roundabout crossings. Report no. MN/RC 2012-28. St. Paul,MN:
Minnesota Department of Transportation.
Insurance Institute for Highway Safety Highway Loss Data Institute. (2017, July).
Roundabouts. Retrieved from https://www.iihs.org/iihs/topics/t/roundabouts/ganda
Rodegerdts, L.; Blogg, M.; Wemple,E.; Myers, E.; Kyte, M.; Dixon, M.; List, G.; Flannery,
A.; Troutbeck, R.; Brilon,W.; Wu, N.; Persaud, B.; Lyon, C.; Harkey, D.; and Carter,
D. 2007. Roundabouts in the United States. National Cooperative Highway Research
Program Report no. 572. Washington, DC: Transportation Research Board.
U.S. Department of Transportation Federal Highway Administration. [USDOTFHWA] (2011,
May 17). Modern Roundabouts:A Safer Choice [Video File]. Retrieved from
https:Ilwwwyoutube.com/watch?v=uhHzly 61WM&feature=youtu.be
U.S. Department of Transportation Federal Highway Administration. (2018, February 6).
Roundabouts and Mini Roundabouts. Retrieved from
https:llsafety.fhwa.dot.gov/intersection/innovative/roundabouts/
Washington State Department of Transportation. (2018). Roundabout benefits. Retrieved
from https://www.wsdot.wa.gov/Safety/roundabouts/benefits.htm
Raised Crosswalks on Entrance to the Roundabout—A Case Study on Effectiveness of
Treatment on Pedestrian Safety and Convenience. Retrieved from
https:llwww.tandfonline.com/doi/abs110.10801153895 88.2013.854885
Separated Bike Lane Planning & Design Guide Documents. Retrieved from
https://www.mass.gov/listslseparated-bike-lane-plan ning-design-guide
Roundabouts, Pedestrian Safety Guide and Countermeasure Selection System. Retrieved from
http:llwww.pedbikesafe.org/PEDSAFEIcountermeasures detail.cfm?CM NUM=25
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Notes