Traffic Safety
Traffic-Safety Department studies safety; maintains more than
1,200 signals & 120,000 road signs
 If
you've ever noticed the safety problems that occur when a traffic
signal goes "black," you can appreciate the vital 24-hours-a-day,
365-days-a-year mission of the Road Commission for Oakland County's
Traffic-Safety Department.
But that's not all. The department also:
- Conducts traffic studies
- Handles pavement marking
- Installs/maintains guard rails, 120,000 traffic signs, and 1,200
signals on all county roads, most state trunk lines, and many
city streets.
The electricity alone for traffic signals costs about $1 million
a year.
Traffic Studies
Based on traffic information, various standards and regulations,
accident pattern statistics and other data, department personnel
conduct studies to evaluate speed limits and the need for new or
different signs or signals. Before they can be installed, traffic
signals must meet criteria called "warrants." Speed studies analyze
driving patterns to see if speed limits should be adjusted -- either
up or down. Studies are also done after major injury or fatality
accidents. Sight distance -- which might limit visibility for drivers
entering roads or intersections -- is also measured, and changes
are made when necessary.
Emergency Services
During power outages, department workers use portable generators
to provide emergency power for traffic signals. They may also place
temporary stop signs at "black" intersections. Repairs and resetting
signal time clocks are done after power is restored. Traffic volume
and intersection visibility problems dictate which signals are serviced
first.
FAST-TRAC
In response to growing traffic congestion and limited funding
for road widening and construction, a computer-controlled traffic
management system called FAST-TRAC was developed.
This innovative, federally-funded system has helped maximize the
capacity of existing roads, improved traffic flow, and reduced serious
intersection accidents. FAST-TRAC has given the Road Commission
a global reputation in Intelligent Transportation Systems (ITS).
Visit the FAST-TRAC section of this
Web site for more information.
Signal Types
Aside from FAST-TRAC signals, three types of signals are used:
pre-timed, semi-actuated, and fully-actuated.
- Pre-timed signals have 24-hour clocks which change signal timing
for morning and evening rush hours, and again when traffic is
lower.
- Semi-actuated signals, often used where side streets meet busy
roads, maintain "green" on the primary road until sensors detect
side-road vehicles and then turn the light green for the side
road.
- Fully-actuated signals have sensors to adjust traffic flow in
all directions. Some traffic signals detect oncoming police, fire,
and ambulance vehicles and automatically give them a green light.
For more information view our Speed Limits publication:
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