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New traffic signals must meet warrants

July 30, 2011
By DAVE WERNER , Adirondack Daily Enterprise

With three new traffic signals being installed this summer in the immediate Malone area, we will explain in this article what goes into the determination on whether or not an intersection should be controlled by stop signs or a full traffic signal.

In all cases, an engineering study is required and is normally conducted by the state Department of Transportation. This study considers traffic conditions, pedestrian characteristics, and physical characteristics of the intersection in question.

Some of the data obtained from the study includes the number of vehicles entering the intersection from each approach, vehicular volumes for each traffic movement from each approach, traffic classification by vehicle type, pedestrian volume counts and whether they are young or elderly.

Other considerations include the physical characteristics of the intersection, vehicle hours of stopped time (vehicles waiting to enter intersection), gaps in traffic on the main street, and crash data.

Federal guidance says a traffic control signal should not be installed unless an engineering study indicates at least one of nine criteria, also known as traffic signal warrants, is met and engineering judgment indicates that a signal would improve the overall safety and operation of the intersection and not seriously disrupt the progressive flow of traffic.

Satisfaction of one or more warrants shall not in itself require the installation of a traffic signal at a given location. Before a final determination is made that a signal should be installed, other remedies, such as turning lanes, should be considered.

The nine warrants considered are:

-Eight-hour vehicular volume - intended for intersections where there is a large volume of intersecting traffic and considers the vehicles per hour on the major street and the minor street over an 8-hour period.

-Four hour vehicular volume - similar to eight-hour warrant but considers four-hour volumes.

-Peak hour - intended for use at a location where traffic conditions are such that for a minimum of one hour the minor street suffers undue delay.

-Pedestrian volume - considered where the traffic volume on the major street is so heavy that pedestrians experience excessive delay in crossing.

-School crossing - intended where the fact that school children crossing the main street is the principal reason to consider a traffic control signal.

-Coordinated signal system - considered where progressive movement in a coordinated signal system necessitates a signal to maintain proper platooning of vehicles. This is not applied where another signal is within 1,000 feet.

-Crash experience - used where the frequency and severity of crashes is the principal reason to consider a signal.

-Roadway network - used to encourage organization of traffic flow on a roadway network (nothing locally).

-Intersection near a railroad crossing - not normally used.

To satisfy the above warrants, tables of vehicle volumes on both the major and minor streets as well as pedestrians are utilized. If the numbers equal or exceed the value in the tables, it may be justification for a signal. It is not a case of just saying "this would be a good place for a signal". As drivers, we all like to think we are also traffic engineers, but we aren't. Let's leave that to those who are.

For more articles on vehicle and traffic law and traffic safety, go to the Traffic Safety Board website at and under departments, click on "Traffic Safety Board."


Dave Werner can be reached at



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