ENGINEERING & TRAFFIC
SURVEY 2025
JIMMIE ZHOU
ASSOCIATE ENGINEER
Public Safety Standing Committee Review
January 28, 2026
TRUE OR FALSE
Many believe that cities select speed limits
The public determines the speed limit
Posting a lower speed limit sign will make
drivers go slower and increase safety
WHAT IS SPEED LIMIT?
Speed limit determinations rely on the premise that a reasonable speed limit is one that conforms to the behavior of most drivers; one will be able to select a speed limit that is both reasonable and effective by measuring drivers'
speeds.
Speed limits set by an Engineering and Traffic Survey (E&TS) are normally set near the 85th percentile speed. The 85th percentile speed is the speed at or below which 85 percent of the traffic is moving, and statistically represents one standard deviation above the average speed.
ROLES
It is not the role of the E&TS to
Lower or raise speed limits
Identify means to lower speed limits or implement
traffic calming measures
Consider emotion, what-ifs or political pressure
It is the role of the E&TS to
Collect data, review roadway characteristics, and
identify the 85th percentile speed
GOALS AND BASIS
SET SPEED LIMIT BASED ON 85TH PERCENTILE SPEED
METHOD
USE ADOPTED SPEED LIMIT FOR SPEED ENFORCEMENT
CA MANUAL ON UNIFORM TRAFFIC CONTROL DEVICES
CALIFORNIA VEHICLE CODE
CA MANUAL FOR SETTING SPEED LIMIT
2025 E&TS FINAL REPORT
CONDUCTED BY TRAFFIC
ENGINEERING FIRM GHD,
INC
SPEED SURVEY
ANNUAL DAILY TRAFFIC
(ADT)
ROADWAY
CHARACTERISTCS
RECOMMENDED SPEED
LIMITS
SAN PABLO MAJOR ROADWAYS
SPEED LIMIT
TABLE
FOR
SAN PABLO
MAJOR
ROADWAY
STAFF RECOMMENDATION
CITY COUNCIL MEETING ON FEBRUARY 2, 2026
TO ACCEPT THE E&TS FINAL REPORT AND ADOPT
THE RECOMMENDED SPEED LIMITS
Questions?