HomeMy WebLinkAbout2017-08-07; Traffic Safety Commission; ; Poinsettia Lane Speed LimitPage 1
CITY OF CARLSBAD TRAFFIC SAFETY COMMISSION STAFF REPORT COMMITTEE MEETING OF: August 7, 2017 ITEM NO. 5-A LOCATION: Poinsettia Lane – Paseo del Norte to Aviara Parkway INITIATED BY: Traffic Safety Commissioners REQUESTED ACTION: Information only BACKGROUND: At their June meeting, Traffic Safety Commission requested staff prepare a presentation on the posted speed limit on Poinsettia Lane between Paseo del Norte and Aviara Parkway. This request was in response to comments made by Vickey Syage during the June Public Comments period of the meeting. SETTING SPEED LIMITS:
A fundamental tenet is that laws are enacted to protect the majority of the public by
regulating the unsafe or unreasonable actions of the few. Establishing defensible speed
limits and installing appropriate signage is critical to successful police enforcement. City
staff follows the California Vehicle Code and Caltrans criteria to propose a legally
defensible speed limit.
In some cases a road meets specific criteria established in the California Vehicle Code
and a default speed limit is established without city council action. For example, a road
that meets the specific criteria to be classified as a resident district can have a posted
speed limit of 25 mph.
In other cases, a “prima facie” speed limit must be established according to the
California Vehicle Code that calls for speed limits to be based on the reasonable speed
for a driver to operate a vehicle under ideal conditions in off-peak free flowing
conditions. City staff use the Caltrans criteria to determine this reasonable speed and
propose a recommended speed limit. Based on staff recommendations, the City Council
adopts an ordinance establishing the speed limit at a public meeting. Appropriate
regulatory speed limit signs are then posted in compliance with the California Manual
on Uniform Traffic Control Devices (CAMUTCD). Police can cite violators that exceed the
posted speed limit with confidence the citation will be upheld in court. When speed
limits have been reasonably set, the enforcement efforts of the Carlsbad Police
Department are more effective.
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Among many factors, the three most persuasive issues considered when setting a
realistic, or rational, speed limit are:
1. 85th percentile speed (critical speed)
2. Collision history
3. Conditions that may not be readily apparent to the driver
The premise implied in speed zoning is that 85% (eighty-five percent) of the drivers
operate their vehicles at a reasonable speed. The 85th percentile speed, often referred
to as the “critical speed”, is the speed which 85% of the drivers are traveling at or
below. Drivers that operate their vehicle at speeds higher than the 85th percentile speed
are considered to be driving at an excessive speed. The speed limit is set at the five mph
increment that is at or just below this critical speed- unless there are conditions not
readily apparent to the driver (e.g., an unusual collision history).
A comprehensive review of the collision history on a roadway is another important
element in the process to establish a speed limit. In the collision analysis, factors such
as collision frequency, type, severity, road conditions, road geometry, lighting
conditions, and spatial distribution of the collisions are all considered. The review of
collisions will also reveal if there is a high incidence of speed-related collisions on the
road at specific locations. However, absent a significant collision history attributed to
speed, it may be concluded that drivers are operating their vehicle in a reasonable and
prudent manner at a speed at or below the critical speed used to establish the speed
limit. If the collision history supports a lower speed limit, or there exist other conditions
not readily apparent to the driver, the speed limit can be established using a speed that
is 5 mph below the critical speed.
Speed limits should not be lowered for conditions that are readily apparent to the
driver, such as driveways with direct access to the road. Conditions not readily apparent
to the driver can be used to lower the speed limit an additional 5 mph, but are
sometimes successfully challenged in court. For unusual conditions or conditions not
readily apparent to motor vehicle operators, appropriate warning devices should be
considered in lieu of lowering the speed limit.
Voluntary public compliance with the posted speed limit is the goal of determining and
posting a realistic prima facie speed limit. A speed limit based on the critical speed
provides for the regulation of unreasonable behavior by a few individuals. A legally
defensible speed limit is based on a factual foundation, fair and reasonable, and related
to roadway risk. Posted speed limits reflect a balance of the various factors specific to
the roadway. As a result, roadway safety can be improved and community concerns
about traffic speed are appropriately and legally addressed.
BASIS OF ACTION:
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The proposed speed limit for the road segment discussed in this report is regulated by
section 22357(a) of the California Vehicle Code: "Whenever a local authority
determines upon the basis of an engineering and traffic survey that a speed greater
than 25 miles per hour would facilitate the orderly movement of vehicular traffic and
would be reasonable and safe upon any street other than a state highway otherwise
subject to a prima facie limit of 25 miles per hour, the local authority may by ordinance
determine and declare a prima facie speed limit of 30, 35, 40, 45, 50, 55, or 60 miles per
hour or a maximum speed limit of 65 miles per hour, whichever is found most
appropriate to facilitate the orderly movement of traffic and is reasonable and safe. The
declared prima facie or maximum speed limit shall be effective when appropriate signs
giving notice thereof are erected upon the street and shall not thereafter be revised
except upon the basis of an engineering and traffic survey. This section does not apply
to any 25 mile per hour prima facie limit which is applicable when passing a school
building or the grounds thereof or when passing a senior center or other facility
primarily used by senior citizens."
DATA:
This portion of Poinsettia Lane is classified as a major arterial and has 2 travel lanes in each direction. The road follows a curvilinear alignment with grades ranging from 1% to 7% and has a curb-to-curb width of 82 feet with landscaped medians. This roadway section does not meet the definition of a resident district according to the California Vehicle Code and a “prima facie” speed limit must be established according to the California Vehicle Code. Signalized intersections exist at Paseo del Norte, Batiquitos Drive, Snapdragon Drive, Crystalline Drive, and Aviara Parkway which are all public streets. Adjacent land uses include single-family & multi-family residential, a fire station and open space. An interchange with Interstate 5 is located on Poinsettia Lane west of Paseo del Norte with nearby land uses including shopping centers and hotels.
As indicated on Table A, staff conducted a speed survey on Poinsettia Lane on January
6, 2010 to obtain data to calculate the critical speed of vehicles. The critical speed, commonly called the 85th percentile speed, is the free flowing speed at which 85 percent of the vehicles are traveling at or below. A sample of 50 vehicles in each
direction of travel was measured to determine the critical speed. The critical speed is an
important factor required to be considered in the evaluation of the appropriate prima
facie speed to post upon a roadway. The pace speed is the 10 mile per hour range of speeds that contain the highest number of observed vehicles. TABLE A SPEED SURVEY DATA FOR POINSETTIA LANE Survey Date
Location
Direction
Critical Speed (MPH)
Pace Speed (MPH)
% in Pace
1/06/10 Poinsettia Lane west of Snapdragon Drive WB/EB 51 41-51 80%
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On January 6, 2010, traffic counts were obtained on Poinsettia Lane to measure the two-way,
24-hour average daily traffic volume. The count data is indicated on Table B.
TABLE B 24-HOUR TRAFFIC VOLUMES
Date Location 24-Hour ADT
1/06/10 West of Aviara Parkway 17,790 Staff reviewed the Police Department traffic collision reports for the two-year period
from January 1, 2008 through December 31, 2009. During that time there were sixteen
(16) reported traffic collision related to speed resulting in a collision rate of 1.16
collisions per million vehicle miles which was significantly lower than the statewide average for roadway sections with similar classification. Based upon the results of the Engineering and Traffic Survey, the Traffic Safety Coordinating Committee recommended establishing a 50 mile per hour prima facie speed limit upon Poinsettia Lane between Paseo del Norte and Aviara Parkway. This speed limit was recommended for approval by the Traffic Safety Commission and approved by the City Council. On January 10, 2017 the Speed and Traffic Survey for this section of roadway was extended for an expiration date of January 6, 2020. (See attached extension letter). Staff reviewed the data used to establish the existing speed limit on Poinsettia Lane between Paseo del Norte and Aviara Parkway at this time and found that it meets the current standards. The current speed limit of 50 mph complies with current vehicle codes and standard Traffic Engineering practices.
Attachments:
1. Engineering and Traffic Survey
2. Extension Letter RECOMMENDATION: None. This item is informational only. NECESSARY CITY COUNCIL ACTION:
None. This item is informational only.
Poinsettia Lane Speed Limit
Paseo del Norte to Aviara Parkway
August 7, 2017
Review of Speed Limit on
Poinsettia Lane
•Public Comment made at June TSC Meeting
•Commissioners requested a review of speed limit
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References
California Vehicle Code
•published by the DMV
•establishes laws governing speed limits
California Manual for Setting Speed Limits
•published by Caltrans
•used to interpret California Vehicle Code
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How Speed Limits are Set in California
•Voluntary compliance is a primary goal
•Drivers determine speed limit, except legally defined
roadways (e.g., residential and business districts)
•Most drivers are rational (85% of drivers)
•Speed limits are established in 5 mph increments
•Speed limit set within 5 mph of 85% speed, except…
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City Traffic Engineer Discretion
5 MPH Reduction
5 mph reduction is allowed if both conditions are met:
1.There is a condition “not readily apparent to driver” (e.g.,
a relatively high collision rate)
2.Must be reduced from the closest 5 mph increment to
85th percentile speed
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Poinsettia Speed Limit
Aviara Parkway to Paseo del Norte
•Not a residential district
•Critical Speed (85th%) used to establish speed limit
•Data Collected January 6, 2010
•Critical speed= 51 mph
•Prima Facie Speed Limit= 50 mph
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Speed Limit Status
•Collision rate below state average
•No issues that are not readily apparent to driver
•Speed & Traffic Survey extended on January 10, 2017
•Expires January 6, 2020
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Staff Recommendation
•Prima facie speed limit on Poinsettia Lane between
Aviara Parkway and I-5 is properly posted at 50 mph
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