1996 Engineering & Traffic SurveyATTACHMENT #1
ENGINEERING AND TRAFFIC SURVEY
Westward Ho Drive (Adams Street to Roadrunner Lane)
Staff recommends this segment of roadway be posted with a prima facie speed limit of thirty five
(35 MPH) miles -per -hour. The existing school zone speed limit will remain at twenty five miles -per
hour (25 MPH) When Children are Present. The recommendation is based on speed survey results
indicating the critical speed is 38 MPH in either direction. Critical speed is defined as the eighty-
fifth percentile speed, which is the speed at or below which 85% of the traffic is moving. The
posted speed limit is normally established by rounding down, (or up), to the first five -mile -per -hour
increment below, (or above), the critical speed, which in this case could be 35 MPH (or 40 MPH).
Rounding down to 35 MPH is justified and recommended based on an evaluation of the existing
street improvements, and overlaid school zone, as addressed in the Speed Analysis below.
Speed data was collected by city engineering staff utilizing the City's S.M.A.R.T. (Speed
Monitoring Awareness Radar Trailer), with the display board unplugged, and speed limit sign folded
down, at the following times and locations:
1) on Tuesday, December 3, 1996, between 10:45 am and 1:45 pm, the SMART was
set up on the south side of Westward Ho Drive, on the sidewalk adjacent to the
football scoreboard, approximately 1000 feet east of Adams Street, picking up
eastbound traffic, recording an 85th percentile speed of 38 MPH, and
2) on Wednesday, December 4, 1996, between 11:15 am and 2:15 pm, the SMART
was set up on the north side of Westward Ho Drive, on the soft sand shoulder,
behind the asphalt berm, across from the High School, adjacent to the Golf Ranch,
approximately 1000 feet west of Dune Palms Road, picking up Westbound traffic,
recording an 85th percentile speed of 38 MPH.
Vehicle speeds on Westward Ho Drive were recorded as they approached the SMART. See
attached speed survey data graphs.
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G:1P W D EPTI C O U N C I U 199 81981217 D. W PD
Engineering and Traffic Survey
Westward Ho Drive (Adams Street to Roadrunner Lane)
Page 2
A review of accident reports indicates four traffic accidents occurred on Westward Ho Drive since
1991, all in 1994. One occurred at the intersection of Dune Palms Road prior to the installation
of the 4 -way stop control. Two of the accidents happened when drivers attempted to swerve to
avoid hitting objects, possibly speed related. The last accident was caused by two vehicles
attempting to enter the left turn lane at the same time, possibly speed related.
♦ POSTED SPEED LIMIT:
♦ DESIGN SPEED:
♦ STREET WIDTH:
♦ LANE CONFIGURATION:
♦ PARKING STATUS:
♦ ACCESS:
♦ SIGHT DISTANCE:
25 MPH "When Children are Present" between Adams Street and
Dune Palms Road; and 25 MPH between Dune Palms Road and
Roadrunner Lane
55 MPH
Varies, 28' to 40'
One lane in each direction, with 1500 ft of left turn lane.
Posted for no on -street parking
Direct access from La Quinta High School driveways, residential
driveways and vacant lot access.
No sight obstructions caused by fixed objects
The study segment is a straight section of roadway, approximately 3800 feet long, intersected by
Adams Street, Dune Palms Road, and Roadrunner Lane. All three intersections are signed with
existing all -way stop configurations.
The portion from Adams Street to Dune Palms Road is the frontage of the La Quinta High School.
The school zone on Westward Ho Drive extends from Adams Street to 500' East of Dune Palms
Road. By State Law, the speed limit through school zones when children are present is 25 MPH.
The portion of Westward Ho Drive to the east from Roadrunner Lane to Jefferson Street meets the
California Vehicle Code definition of a residential street, and is posted as 25 MPH in both
directions.
Due to the neighboring 25 MPH residential zone, and 25 MPH when children are present school
zone, the speed limit should be reduced to a prima facie speed limit of 35 MPH.
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GAPWD EMCOUNCI01 OW961217D.WPD
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SMART SURVEY SUMMARY
<Westward Ho Dr., Eastbound Traffic, l000 ft e/o Adams>
<cl6a'r'-dry>�-"ft
POSTED SPEED LIMIT: <25 MPH (When Children are Present)>
SURVEY STARTED: <96/12/03 10:56>
MIN SPEED ALLOWED <10> MAX SPEED ALLOWED <70>
TIME 10:45 11:00 11:15 11:30 11:45 12:00 12:15 12:30 12;45 13:00 13:15 13:30 13:45
VEH. 3 7 14
12 13 25
18 30 12 14 22
31 3
AVG. 30.0 31.1 33.1
28.8 31.9 34.4
30.9 31.0 28.8 32.0 32.7
33.0 15.0
TOTAL VEHICLES
= 204
MINIMUM SPEED = 15
MAXIMUM SPEED = 52
AVERAGE SPEED
= 31.66
50th PERCENTILE =
31 85th PERCENTILE = 38
TEN MILE PACE
= 27 to 36
END OF
REPORT
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