HomeMy WebLinkAbout2006-11-06; Traffic Safety Commission; ; Establish a prima facie speed limit upon Tamarack Avenue easterly of College Boulevard(
CITY OF CARLSBAD
TRAFFIC SAFETY COMMISSION
STAFF REPORT
COMMISSION MEETING OF: November 6, 2006 ITEMNO.6A
LOCATION: Tamarack Avenue from College Boulevard (South) to College Boulevard (North)
INITIATED BY: Matt Law, 3750 Caldera Place, Carlsbad, CA 92010
REQUESTED ACTION: Establish a prima facie speed limit upon Tamarack Avenue easterly
of College Boulevard
BACKGROUND:
Tamarack A venue, easterly of College Boulevard, is a two-lane roadway that serves
single-family residences and the Calavera Hills Elementary School and Calavera Hills
Middle School located in the northeast portion of Carlsbad. The road was opened to
traffic in 2000.
SETTING SPEED LIMITS:
Optimal 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. Most drivers
operate vehicles in a reasonable manner. Traffic laws established on the basis of the
behavior of the reasonable and prudent motorist are found to be the most successful.
Roads in Carlsbad are designed in accordance with engineering standards to satisfy the
goals of a safe roadway and to enhance efficient traffic flow. One way to achieve the
goals is to establish proper and reasonable speed limits that can be enforced. Speed limits
that are reasonable can help to achieve voluntary compliance by the majority of drivers
without need for the presence of a police officer. Laws and/or the establishment of speed
zones that arbitrarily restrict travel by the majority of motorists can lead to wholesale
violations of the posted speed limit.
In the City of Carlsbad, the predominant practice for managing speed is by legally
establishing a prima facie speed limit and then posting the speed limit upon the road with
regulatory signs. A prima facie speed limit recognizes that conditions change throughout
the day and there is no one safe speed for all the conditions that may be present upon the
roadway. Police enforcement is used to target the most egregious violators of the speed
limit. 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.
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CITY OF CARLSBAD
TRAFFIC SAFETY COMMISSION
STAFF REPORT
COMMISSION MEETING OF: November 6, 2006
( continued)
ITEMNO. 6A
Nationally recognized vetted practices and guidance per standards and procedures in the
California Manual on Uniform Traffic Control Devices (FHW A's MUTCD Revision 1,
as amended for use in California) are considered when setting speed limits. 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. Prima facie speed limits are established by law when the City
Council adopts an ordinance and the speed limit is posted on the roadway to indicate the
maximum reasonable speed for a driver to operate a vehicle under ideal conditions in
off-peak free flowing conditions. Among many factors, the three most persuasive
arguments to consider when 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
The premise implied in sgeed zoning is that the majority of drivers are operating their
vehicles at or near the 851 percentile speed. Drivers that operate their vehicle at speeds
higher than the 85th percentile speed should be the focus of the police. An important speed
zoning concept is that the disparity in speed between vehicles on the road is reduced
when prima facie speed limits are established at or near the 85th percentile speed and,
as a result, safety is enhanced. Also, a speed limit that is established based upon the
85th percentile speed will increase driver respect for the speed limit sign. Only those signs
that have the respect of the roadway user will have a positive effect to control 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 there is a high incidence of speed-related
collisions on the road at specific locations. Absent a significant collision history
attributed to speed, it can be concluded that drivers are operating their vehicle in a
reasonable and prudent manner at the speed they chose to drive.
The installation of a speed limit sign does not automatically decrease accident rates nor
increase roadway safety. Speed limits should not be lowered for conditions that are
readily apparent and the speed limit signs are not used as intersection, curve or hazard
warning devices. For the unusual conditions or conditions not readily apparent to drivers,
appropriate warning signs are installed.
Design factors such as the geometric elements of the road, sight distance, or other factors
may have a significant impact on the free flowing speed chosen by drivers. This driver
chosen speed, in tum, is considered when establishing a prima facie speed limit.
(
CITY OF CARLSBAD
TRAFFIC SAFETY COMMISSION
STAFF REPORT
COMMISSION MEETING OF: November 6, 2006
( continued)
ITEMNO. 6A
A number of factors may be considered when establishing a prima facie speed limit.
The California Manual on Uniform Traffic Control Devices lists such factors as:
A. Road characteristics, shoulder condition, grade, alignment, and sight distance;
B. The pace speed;
C. Roadside development and pedestrian 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 determining a realistic prima facie speed limit to
establish. 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. A posted speed limit should be readily accepted by drivers,
be fair and reasonable, be related to risk on the roadway, be determined by the majority of
drivers, and one that has a factual foundation.
DATA:
Tamarack A venue is unclassified on the Circulation Element of the General Plan.
It functions as a collector street and is 0.91 miles in length. Traffic lanes are separated by
a double-yellow striped centerline, and the road has a curb-to-curb width of 40 feet.
Tamarack A venue has been constructed to City standards with curb and gutter,
contiguous sidewalks, bicycle lanes, and street lights.
Six driveways and a total of eight streets intersect this portion of Tamarack A venue.
Of the eight intersections, an all-way stop has been established at three intersections:
Levee Drive, Knollwood Drive, and Strata Drive (N). Traffic signals have been installed
at both locations where Tamarack A venue intersects College Boulevard.
Tamarack A venue follows a curvilinear alignment and has centerline grades that vary
from 0.50% to 9.39%. The minimum roadway centerline radius that was constructed on
Tamarack A venue was 300 feet. This exceeds the minimum 200-foot centerline radius
required by Carlsbad Engineering Standards for a local road and meets the minimum
300-foot radius required for a collector road.
( (
CITY OF CARLSBAD
TRAFFIC SAFETY COMMISSION
STAFF REPORT
COMMISSION MEETING OF: November 6, 2006 ITEMNO. 6A
( continued)
Traffic volumes on Tamarack Avenue vary from 818 vehicles per day near Knollwood
Drive to 2,764 vehicles east of College Boulevard (S). Both counts were obtained in
May 2006.
Staff conducted two speed surveys on Tamarack Avenue on June 6 and 7, 2006
to determine the critical speed of vehicles. The critical 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 California Manual on Uniform Traffic
Control Devices (FHWA's MUTCD 2003 Revision 1, as amended for use in California)
provides guidance when a speed limit is to be posted. It states that " .. .it should be
established at the nearest 10 km/h or 5 mph increment of the 85th percentile speed of
free-flowing traffic". As an option, the California MUTCD states that "The posted speed
limit may be reduced by 10 km/h (5 mph) from the nearest 10 km/h or 5 mph increment
of the 85th percentile speed, where engineering study indicates the need for a reduction in
speed to match existing conditions with the traffic safety needs of the community".
California Vehicle Code section 627 defines the term "Engineering and Traffic Survey"
and lists its requirements, as follows:
627. (a) "Engineering and traffic survey," as used in this code, means a survey of highway
and traffic conditions in accordance with methods determined by the Department of
Transportation for use by state and local authorities.
(b) An engineering and traffic survey shall include, among other requirements
deemed necessary by the department, consideration of all of the following:
(1) Prevailing speeds as determined by traffic engineering measurements.
(2) Accident reports.
(3) Highway, traffic, and roadside conditions not readily apparent to the driver.
(c) When conducting an engineering and traffic survey, local authorities, in
addition to the factors set forth in paragraphs (1) to (3), inclusive, of subdivision (b) may
consider all of the following:
(1) Residential density, if any of the following conditions exist on the particular
portion of highway and the property contiguous thereto, other than a business district;
(A) Upon one side of the highway, within a distance of a quarter of a mile, the
contiguous property fronting thereon is occupied by 13 or more separate dwelling houses
or business structures.
(B) Upon both sides of the highway, collectively, within a distance of a quarter of a
mile, the contiguous property fronting thereon is occupied by 16 or more separate
dwelling houses or business structures.
(C) The portion of highway is longer than one-quarter of a mile but has the ratio of
separate dwelling houses or business structures to the length of the highway described in
either subparagraph (A) or (B).
(2) Pedestrian and bicyclist safety.
( (
CITY OF CARLSBAD
TRAFFIC SAFETY COMMISSION
STAFF REPORT
COMMISSION MEETING OF: November 6, 2006
( continued)
ITEMNO. 6A
Staff completed the Engineering and Traffic Survey (attached) for Tamarack Avenue
from Tamarack A venue (south) to Tamarack A venue (north). Results of the speed survey,
contained within the Engineering and Traffic Survey that was conducted on Tamarack
A venue, are summarized in Table A.
TABLE A
SPEED SURVEY DATA FOR TAMARACK A VENUE
250' e/o Hummock Drive
125' w/o Caldera Place
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 authorities 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 occurred 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.
For the two year period from September 1, 2004 through August 31, 2006, there was one
collision reported on the portion of Tamarack A venue east of College Boulevard.
Tamarack A venue (S) intersects College Boulevard in a four-leg, signalized intersection.
The portion of Tamarack A venue westerly of College Boulevard has a posted prima facie
speed limit of 35 miles per hour.
RECOMMENDATION:
Based upon the results of the Engineering and Traffic Survey, the Traffic Safety
Coordinating Committee recommends establishing a 30 mile per hour prima facie speed
limit upon the loop portion of Tamarack A venue located easterly of College Boulevard.
NECESSARY CITY COUNCIL ACTION:
An ordinance will be required to be adopted by the City Council to establish the 30 mile
per hour prima facie speed limit, as recommended.
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LOCATION MAP
CITY OF OCEANSIDE
CITY OF CARLSBAD
----
PROPOSED
SPEED
ZONE
LEGEND:
@ TRAFFIC SIGNAL
[II ALL-WAY STOP
PROJECT NAME
PROPOSED SPEED ZONE
DRA't'rN BY: SCOTT EVANS, CARLSBAD ENGINEERING DEPT. 1 18 05 C: TRAFFIC SPEED ZONES SPEED ZONE-TAMARACK A\IE2.DWG
NOT TO SCALE
EXHIBIT
1
( CITY OF CARLSBAD
ENGINEERING AND TRAFFIC SURVEY
STREET: Tamarack Avenue
LIMITS: College Boulevard (N) to College Boulevard (S)
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:
{9/01/04 through 8/31/06)
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
Direction: Eastbound/Westbound
6/06/06
250' e/o Hummock Drive
31 MPH
23 to 33 MPH
91%
No Posted S eed Limit
0
1
0.84
1.89 (2004 Rate for 2-Lane Roadway)
Direction: Eastbound/Westbound
6/07/06
125' w/o Caldera Place
33 MPH
26 to 36 MPH
89%
No Posted S eed Limit
2,764 -East of College Blvd. (S) (5/17/06); 818 -North of Knollwood Or. (5/16/06)
Traffic Signals at College Boulevard (N&S); Stop Sign Control at Levee Drive,
Knollwood Drive, and Strata Drive (N)
Light
Bicycle Lane on Each Side
Parking Prohibited on Each Side
Unclassified
0.91 Mi.
40 Feet (Curb-to-Curb)
One Lane Each Direction
Roadway Centerline Grades Vary from 0.50% to 9.39%
Curvilinear
Sidewalk on Each Side
Six Driveways
Street Lights on Each Side
E. Special Conditions: This portion of Tamarack Avenue traverses a residential area and connects to College Boulevard at each
end. Travel lanes are separated by a double-yellow centerline. Traffic enters the street from the elementary/middle school exit
driveway and nine public streets. Warning signs stating SCHOOL -SPEED LIMIT 25 -WHEN CHILDREN ARE PRESENT
are posted approaching the elementary/middle school entrance and approaching the elementary/middle school exit. Yellow school
crosswalks are stri ed at Colle e Boulevard both intersections , Levee Drive, Knollwood Drive, and Strata Drive N .
F. Adjacent Land Uses: Single-Family Residential, Elementary School, Middle School, Open Space, Two Tot Lots, Picnic Area,
Corner Park with Basketball Court.
G. Remarks/Conditions Not Readily Apparent: The adjacent picnic areas, tot lots, basketball court, and open space attract
edestrians that cross the roadwa at various locations.
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 California Manual on Uniform Traffic Control Devices
for Streets and Highways (FHWA's MUTCD 2003 Edition, as amended for use in California) with respect to design and prevailing
speeds, accident records, pedestrian and bicyclist safety, intersection and driveway spacing, and roadside and traffic conditions
not readil a arent to the driver. A s eed limit ostin of 30 MPH is found to be a ro riate and ·ustified.
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CITY OF CARLSBAD
SPEED SURVEY
(
DATE: 6/06/06 TIME: 9:35 AM TO 3:05 PM TOTAL VEHICLES:
WEATHER: Overcast CRITICAL SPEED:
LOCATION: Tamarack Avenue-250' e/o Hummock Drive VEHICLES IN PACE:
OBSERVER/RECORDER: J. Gale/J. Murray PACE SPEED(S):
·NONE
POSTED SPEED LIMIT
EASTBOUND
DIRECTION OF TRAVEL
MPH # % !: # % %tile % #
65
64
63
62
61
60
59
58
57
56 .'
55
54
53
52
51
50
49
48
47
46
45
44
43
42
41
40
39
38
37
36
35 X X
34 X
33 X
32 X X X X
31 X X X X
30 X X
29 X X X X X X X X X
28 X X X X X X X
27 X X X X X
26 X X
25 X X X X
24 X X
23 X
22 X X
21
2 4 2 2 100
1 2 3 3 98 4 2
1 2 1 1 95
4 8 7 7 94 6 3
4 8 6 6 87 4 2
2 4 7 7 81 10 5
10 20 15 15 74 10 5
8 16 10 10 59 4 2
6 12 15 15 49 18 9
3 6 11 11 34 16 8
4 8 12 12 23 16 8
2 4 4 4 11 4 2
1 2 4 4 7 6 3
2 4 3 3 3 2 1
Engineering Department
Transportation Division
---------------
100
31 MPH _____ ...;c.,,;.. ____ _
91 % _____ .,;;,_;_ ____ _
23 TO 33 MPH ----------
WESTBOUND
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
44
43
42
41
40
39
38
37
36
35
X X 34
33
X X X 32
X X 31
X X X X X 30
X X X X X 29
X X 28
X X X X X X X X X 27
X X X x· X X X X 26
X X X X X X X X 25
X X 24
X X X 23
X 22
21
DATE: 6/07/06 TIME: 1:15 PM TO
CITY OF CARLSBAD
SPEED SURVEY
! .
3:00 PM TOT AL VEHICLES:
WEATHER: Overcast & Cool CRITICAL SPEED:
LOCATION: Tamarack Avenue.~125' w/o Caldera Place VEHICLES IN PACE:
OBSERVER/RECORDER: J. Gale PACE SPEED(S): ---------
-NONE
POSTED SPEED LIMIT
EASTBOUND
DIRECTION OF TRAVEL
MPH # % :E # % %tile % #
65
64
63
62
61
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
43
42
41
40
39
38
37
36 X
35 X
34 X X X
33 X X X X
32 X X X X X X
31 X X X X
30 X X X X X X X X
29 X X X X X X X X
28 X X X X X X X X
27 X X X X X
26 X
25
24 X
23
22
21
1 2 2 2 100 2 1
1 2 3 3 98 4 2
3 6 6 6 95 6 3
4 8 5 5 89 2 1
6 12 11 11 84 10 5
4 8 11 11 73 14 7
8 16 16 16 62 16 8
8 16 16 16 46 16 8
8 16 11 11 30 6 3
5 10 12 12 19 14 7
1 2 4 4 7 6 3
1 1 3 2 1
1 2 2 2 2 2 1
Engineering Department
Transportation Division
100
------'3~3;._ ____ MPH
95 % -----------
26 TO 36 MPH ----------
WESTBOUND
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
44
43
42
41
40
39
38
37
X 36
X X 35
X X X 34
X 33
X X X X X 32
')( X X X X X X 31
X )( X X X X X X 30
X X X X X X X X 29
X X X 28
X X X X X X X 27
X X X 26
X 25
X 24
23
22
21