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An Overview!
What are
traffic signals?
Traffic signals are the red, yellow and green lights used
at busy intersections to alternately direct approaching traffic
to stop and, then, to proceed. When installed at the proper location
and under the appropriate conditions, a traffic signal can reduce
traffic delays and enhance safety.
Not a universal
solution.
There is a widely-held belief that a traffic signal can
solve all or most intersection traffic problems. But, under the
wrong circumstances, a traffic signal can cause unnecessary delay,
waste taxpayer dollars, and actually increase accidents. Simpler
measures often work better.
Why this
pamphlet?
This pamphlet was prepared to provide you with a
better understanding about what a traffic signal can do, what it
cannot do, what traffic engineers can do to improve safety
and reduce delays at an intersection, and what happens
when it is determined that a traffic signal is the best
solution.
What Can A Traffic Signal Do?
What a signal
does.
A traffic signal sequentially assigns the right-of-way to
vehicles approaching an intersection from various directions, forcing
the streams of traffic to take turns entering the intersection.
A signal stops traffic in one or more directions so that:
- Vehicles
on the side street can cross or enter a heavy flow of traffic
- Vehicles
can turn left from the opposite direction
- Pedestrians
can cross a street with little or no vehicle interference
Most signals
include vehicle detecting devices, usually imbedded in the roadway,
that sense traffic approaching from each direction and adjust signal
timing for maximum efficiency.
How a signal might help.
A signal can reduce the delay to those waiting to
enter or cross a heavy stream of traffic and reduce the potentially
hazardous conflicts between traffic movements, thereby reducing
the likelihood of certain types of collisions. At certain locations
it can help establish a "signal progression," where
traffic can continue along a route at a reasonable, constant speed
and with minimal delay.
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