City of San Marino Traffic Safety Measures
U: HUTOAD
LCBAMBO
nan
3. Imalra and Dus
Criah Fase
z
City of San Marino
Engineering and Traffic Burvery
Summary
Data Collection and Tasks to Complete Survey
H
Gothel Se
C
D
SHAZHE
1.
Chan
Matast
ad
*
S
Cond
To
T
'
CC::M
·
T
588
P
regi
Singh of
Ser
Dolact
G
5. Condom held by opa
Mature
SUC
admr Lei
Appear tortafor
Cky of San Marino
Public Works Department
CH
Rader Survey Shwet
45
2 Peter Speed
Sant Perers le Speed
10
25
30
я
35
122
Total Semples
Buy LAM
arantira L
LA
Pass Anal 25
1ch Peru
Speed
2
21-23
14
KE
Peer Pac
130%
2.
3.
4.
A field review of each of the survey segments is performed to determine highway, traffic and roadside characteristics
which may not be readily apparent to the motorist, as well as to check the condition of existing speed limit signs and
review speed limits that are posted on streets that continue through City limits to an adjacent city.
Field radar surveys are conducted to obtain representative speeds on each survey segment. Typically 100 samples are
collected for each direction separately on each street segment. The survey period is typically limited to one hour or until
at least 50 samples in each direction are collected. Speed measurements are taken during off-peak hours in an unmarked
vehicle on weekdays to minimize the effects of traffic congestion on vehicular speed. If there is difficulty in obtaining the
minimum sample size, measurements will be taken during any period with free-flowing traffic. The collected data is
summarized for each segment and direction in tabular form.
A statistical analysis of the field speed checks is performed. The field information and radar samples are input into the
Crossroads speed survey program along with the accident data, average daily traffic and street lengths.
Accident rates are determined for each segment based on the segment length, number of accidents, and daily traffic
volumes. These rates are compared with the average rates for roadways with similar characteristics to determine if the
accident incidence is greater than what is typically expected. Accident information was compiled using the latest 3 years
from SWITRS (Statewide Integrated Records System) reports from 2016-2018.
5. Speed limit recommendations are developed utilizing information obtained from the above tasks.
6.
7.
A summary of the field data is then generated for each segment. The summary includes a tally of the radar
measurements and the 15th percentile, 50th percentile and 85th percentile (critical) speeds and 10 mph pace speeds for
each direction on each segment. Recommendations for the posted speed limits are based on the measured speeds,
accident incidence, and review of conditions not readily apparent to the driver. Any reduction or increase in posted
limits are fully justified, explained, and approved by a Registered Civil Engineer or Traffic Engineer.
As part of the speed survey effort 24-hour tube counts (bi-directional) were also collected. 24-hour counts were taken on
a Tuesday, Wednesday or Thursday on a typical weekday.
Citys
SAN MARINO
CALIFORNIA
8
TRANSTECH
Est. 1989View entire presentation