HomeMy WebLinkAbout2005-12-05; Traffic Safety Commission; ; Establish a prima facie speed limit upon Alicante Road from Alga Road to Poinsettia Lane( (
CITY OF CARLSBAD
TRAFFIC SAFETY COMMISSION
STAFF REPORT
COMMISSION MEETING OF: December 5, 2005
LOCATION:
INITIATED BY:
Alicante Road, Alga Road to Poinsettia Lane
Deputy City Engineer, Transportation
ITEMNO.6B
REQUESTED ACTION: Establish a prima facie speed limit upon Alicante Road from
Alga Road to Poinsettia Lane
BACKGROUND:
Alicante Road is a two-lane local road traversing a curvilinear alignment between
Alga Road and Poinsettia Lane (see Exhibit 1). Currently, Alicante Road terminates at
Poinsettia Lane for public traffic use. In the future, Alicante Road will be extended
northerly to provide access to the Bressi Ranch development and to serve the Alga Norte
Community Park. South of Alga Road, Alicante Road has a posted speed limit of
40 miles per hour.
SETTING SPEED LIMITS:
Mobility is enhanced and overall traffic flow improved when drivers are operating their
vehicles at a speed that is reasonable and safe. In fact, the premise of CVC section 22350,
Basic Speed Law, is that no person shall drive upon a road at a speed greater than is
reasonable and prudent taking into account weather, visibility, and traffic on the road and
in no event at a speed that endangers the safety of others.
Carlsbad roads are designed using engineering standards to promote the goals of safety
on the roadway and efficient traffic flow. One way to achieve the goals is to establish
reasonable speed limits that can be enforced. Speed limits that are reasonable help
achieve voluntary compliance by the majority of drivers without need for the presence of
a police officer.
In Carlsbad, the most predominant practice of managing speed is by legally establishing a
speed limit and posting the speed limit upon the road with signs. Police enforcement is
used to target the most egregious violators of the speed limit.
The most common method of establishing speed limits incorporates traffic engineering
principles and other factors, such as using the results of a speed survey, into the Traffic
and Engineering Survey. The three most persuasive arguments for setting a realistic, or
rational, speed limit are:
1. Critical speed (85th percentile speed)
2. Collision history
3. Conditions that may not be readily apparent to the driver
CITY OF CARLSBAD
TRAFFIC SAFETY COMMISSION
STAFF REPORT
COMMISSION MEETING OF: December 5, 2005
(continued)
ITEMNO. 6B
The premise in speed zoning is that the majority of drivers are traveling at or near
the 85 th percentile speed. Drivers that operate their vehicle at speeds higher than the
85th percentile speed would be the focus of the police. The disparity in speed of vehicles
on the road is reduced when speed limits are established at or near the 85th percentile
speed and this results in enhanced safety. Also, a speed limit that is established based
upon the 85th percentile speed will increase respect for the speed limit sign. Only those
signs that have the respect of the roadway user will have an effect in controlling traffic.
A review of the collision history on a roadway is an important element in the process to
establish a speed limit. The review will reveal if speed-related collisions occur in a high
incidence on the road at certain locations. Consequently, factors such as the geometric
elements of the road, sight distance, or other factors may have a significant impact on the
speed chosen by drivers. Absent a significant collision history as a result of speed, it can
be concluded that drivers are operating their vehicle in a reasonable and prudent manner
at the speed they chose to drive. This driver chosen speed, in tum, is used in establishing
a speed limit.
A number of factors may be considered when establishing a speed limit. The 2003
MUTCD lists such factors as:
A. Road characteristics, shoulder condition, grade, alignment, and sight distance;
B. The pace speed;
C. Roadside development and activity; and
D. Reported crash experience for at least a 12-month period.
As stated, basic speed law requires drivers to operate their vehicle at a speed that takes
into account all roadway factors, environmental elements, adjacent land uses, and other
traffic on the road. These are, in general, all readily apparent factors. Warning signs
placed on the roadway can alert drivers to the presence of an unseen or unanticipated
condition. As a result, drivers can operate their vehicle in a reasonable and prudent
manner by adjusting speed for the condition that may be encountered.
In summary, through the use of engineering, educational, and enforcement techniques,
the management of vehicle speed is conducted. Voluntary public compliance with the
posted speed limit is the goal when setting a realistic speed limit. The realistic speed limit
takes into consideration the normally competent and careful actions of a reasonable driver
and provides for the regulation of unreasonable behavior by a few individuals.
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CITY OF CARLSBAD
TRAFFIC SAFETY COMMISSION
STAFF REPORT
COMMISSION MEETING OF: December 5, 2005
(continued)
DATA:
ITEMNO. 6B
Alicante Road is a residential serving road located in the Villages of La Costa
development. It opened in April 2005 and is 1.13 miles in length. There is a 750-foot
segment of Alicante Road north of Alga Road that has a landscaped median dividing both
directions of travel. The remaining portion of roadway has a double-yellow centerline
stripe with one travel lane in each direction.
Although it is unclassified on the Circulation Element of the General Plan north of
Alga Road, Alicante Road functions as a local collector road. A collector road has a daily
traffic volume capacity range of between 2,000 and 10,000 vehicles. The road follows a
curvilinear alignment with centerline horizontal geometrics as indicated on Exhibit 2.
In accordance with Engineering Department design criteria, the minimum centerline
radius for a collector road is 300 feet. Centerline vertical grades on Alicante Road range
from 1 % to 11.6%.
A traffic count was obtained at two locations on Alicante Road on November 9, 2005 to
determine the two-way, 24-hour average daily traffic volume. The recent count data is
indicated on Table A.
. Date .
11/09/05
11/09/05
TABLE A
24-HOUR TRAFFIC VOLUMES
ALICANTE ROAD
': 24lHour JU)T: : ; ' ..
NB·, '"'SB ·
Poinsettia Lane to La is Road 721 708
Galena A venue to Al a Road 935 914
. . ~'-. _, ;, ~-:-,... "" ,. .. _...,. :"· . .-.,,
1,429
1,849
Staff conducted a speed survey on Alicante Road on November 8, 2005 to determine the
critical speed of vehicles. The c1itical speed, commonly called the 85th percentile, is the
speed at which 85 percent of the vehicles are traveling at or below. A sample of 100
vehicles was measured to determine the critical speed. The critical speed is used to help
determine the appropriate prima facie speed to post upon a roadway.
The 85th percentile speed has been determined throughout the United States to generally
conform to a safe and reasonable speed limit. The 2003 Manual on Uniform Traffic
Control Devices (MUTCD) California Supplement provides guidance when a speed limit
is to be posted. It states that "the speed limit should be established at the nearest 10 km/h
(5 mph) increment to the 85th percentile speed. However, in matching existing conditions
with the traffic safety needs of the community, engineering judgment may indicate the
need for a further reduction of 10 km/h (5 mph)."
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CITY OF CARLSBAD
TRAFFIC SAFETY COMMISSION
STAFF REPORT
COMMISSION MEETING OF: December 5, 2005
(continued)
ITEMNO. 6B
California Vehicle Code section 627 defines the term "Enginee1ing and Traffic Survey"
and lists its requirements. Staff completed an Engineering and Traffic Survey (attached)
for Alicante Road from Alga Road to Poinsettia Lane. Results from the speed survey,
included as part of the Engineering and Traffic Survey that was conducted on
Alicante Road, are summarized in Table B.
Surv:ey ••
Date •
11/08/05
TABLEB
SPEED SURVEY DATA FOR ALICANTE ROAD
Location:/·
100' n/o Citrine Drive 41 32-42
-~--~!\ Pacer,
80
The pace speed is the 10 mile per hour range of speeds that contain the highest number of
observed vehicles. Generally, the critical speed is in the upper range of the pace speed.
Sections 22357 and 22358 of the California Vehicle Code authorize local authmities to
establish a prima facie speed limit on the basis of the results of an Engineering and
Traffic Survey. The Engineering and Traffic Survey considers such factors as the number
of collisions that have occuned on the road segment, roadway features, adjacent land
uses, driveway locations, traffic volumes, pedestrian volumes, critical speed, horizontal
and vertical alignment, stopping sight distance, and conditions that may not be readily
apparent to the driver.
Staff has reviewed the Police Department collision reports for the time period from the
date that the road opened in early April. One collision has been reported on this new
roadway segment. It was a hit and run collision that resulted when the vehicle ran off the
road and knocked over a street light pole. The driver abandoned the vehicle. The short
duration for the reporting period, combined with low traffic volumes, results in a high
collision rate at this time that is not expected to be the collision rate for Alicante Road in
the future.
Alicante Road intersects Alga Road as a four-leg intersection controlled with a traffic
signal. At the intersection of Alicante Road with Poinsettia Lane, right-of-way
assignment also is controlled with a traffic signal. This intersection essentially functions
as a T-intersection for the public with Alicante Road north of Poinsettia Lane being
authorized for construction vehicles only.
RECOMMENDATION:
Based upon the results of the Engineering and Traffic Survey, the Traffic Safety
Coordinating Committee recommends establishing a 40 mile per hour prima facie speed
limit upon Alicante Road from Alga Road to Poinsettia Lane.
NECESSARY CITY COUNCIL ACTION:
An ordinance will be required to be adopted by the City Council to establish the 40 mile
per hour prima facie speed limit, as recommended.
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LOCATION MAP
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PROPOSED
SPEED ZONE
NOT TO SCALE
PROJECT NAME
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AL/CANTE ROAD
PROPOSED SPEED ZONE
DRAllrN BY: SCOTT EVANS, CARLSBAD ENGINITRING DEPT. B/18/05 C: \ TRAFF1C\SPEED ZONES\SPEED ZONE~AUCANTE ROAD NOR"1.DWG
EXHIBIT
1
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LOCATION MAP
----328.65'
NOT TO SCALE
113.67'-------------
,---------------' ' ' \ LAPIS RD. (S)
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PROJECT NAM£
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ALICANTE ROAD
HORIZONTAL ALIGNMENT
EXHIBIT
2
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CITY OF CARLSBAD
ENGINEERING AND TRAFFIC SURVEY
STREET: Alicante Road
LIMITS: Poinsettia Lane to Alga Road
A. Prevailing Speed Data:
Date of Speed Survey
Location of Speed Survey
85th Percentile
10 MPH Pace
Percent in Pace
Posted S eed Limit
B. Midblock Accident History:
(4/01/05 through 8/31/05; New Roadway)
Speed-Related Accidents
Total Accidents
Accidents/Million Vehicle Miles (MVM)
California Statewide Accidents/MVM
C. Traffic Factors:
Average Daily Traffic
Traffic Controls
Pedestrian/Bicycle Traffic
Bicycle Lanes
On-Street Parkin
D. Roadway Factors:
Street Classification
Length of Segment
Roadway Width
Number of Lanes
Vertical Alignment
Horizontal Alignment
Sidewalks
Driveways
Street Li htin
0
1
Direction: Northbound/Southbound
11/08/05
100' n/o Citrine Drive
41 MPH
32 to 42 MPH
80%
No Posted S eed Limit
*3.53 (see Section E.)
2.04 2003 Rate for Same T e of Roadwa
1,429 -South of Poinsettia Lane (11/09/05); 1,849 -North of Alga Road (11/09/05)
Traffic Signals at Poinsettia Lane and Alga Road
Light
No Designated Bicycle Lanes Have Been Striped on the Roadway
Parking Allowed on Majority of Each Side
Unclassified
1.13 Mi.
40 to 52 Feet (Curb-to-Curb)
One Lane Each Direction
Roadway Grades Vary from 1 % to 11.6%
Curvilinear
5-Foot Sidewalk on East Side; 10-Foot Sidewalk/Bike Path on Majority of West Side
One Driveway
Street Lights on Each Side
E. Special Conditions: Travel lanes are separated by a double-yellow centerline, except for southerly 750 feet of segment which is
separated by a raised, landscaped median. This portion of Alicante Road serves as a connection between Poinsettia Lane and
Alga Road, both major arterials. *Though only one accident occurred since the roadway opened to the public in early April 2005,
the accident rate of 3.53 is artificial! hi h because it is based on 153 da s, not the customa 730 da s two ears .
G. Remarks/Conditions Not Readll A arent: Construction activit is on oin ad·acent to ma·orit of the roadwa section.
H. Traffic Engineer's Recommendation (Explanation): This speed zone satisfies the conditions of Section 627 of the California
Vehicle Code and has been prepared and evaluated in accordance with the Manual on Uniform Traffic Control Devices (MUTCD)
2003 Edition as amended by the MUTCD 2003 California Supplement with respect to design and prevailing speeds, accident
records, pedestrian and bicyclist safety, intersection and driveway spacing, and roadside and traffic conditions not readily
a arent to the driver. As eed limit ostin of 40 MPH is found to be a ro riate and ·ustified.
DATE: 11/08/05 TIME: 10:20 AM TO
WEATHER: Partly Cloudy
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CITY OF CARLSBAD
SPEED SURVEY
12:10 PM TOTAL VEHICLES:
CRITICAL SPEED:
LOCATION: Alicante Road~100' n/o Citrine Drive VEHICLES IN PACE:
OBSERVER/RECORDER: J. Gale ---------PACE SPEED(S):
NONE
POSTED SPEED LIMIT
SOUTHBOUND
DIRECTION OF TRAVEL
MPH # % l: # % %tile % #
65
64
63
62
61
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
43 X X X
42 X
41 X X
40 X X X X X X
39 X X X X X X X
38 X X X X
37 X X X X
36 X X X X X X
35 X X X X X
34 X X X X X
33 X
32 X X X
31 X X
30 X
29
28
27
26
25
24
23
22
21
2 2 100 4 2
3 6 5 5 98 4 2
1 2 4 4 93 6 3
2 4 7 7 89 10 5
6 12 9 9 82 6 3
7 14 14 14 73 14 7
4 8 6 6 59 4 2
4 8 5 5 53 2 1
6 12 10 10 48 8 4
5 10 10 10 38 10 5
5 10 7 7 28 4 2
1 2 6 6 21 10 5
3 6 6 6 15 6 3
2 4 4 4 9 4 2
1 2 '4 4 5 6 3.
1 1 1 2 1
Engineering Department
Transportation Division
100
41 MPH ----------
80 % ----------
32 TO 42 MPH -----
NORTHBOUND
DIRECTION OF TRAVEL
MPH
65
64
63
62
61
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
X X 44
X X 43
X X X 42
X X X X X 41
X X X 40
X X X X X X X 39
X X 38
X 37
X X X X 36
X X X X X 35
X X 34
X X X X X 33
X X X 32
X X 31
X X X 30
X 29
28
27
26
25
24
23
22
21