Frequently Asked Questions on Traffic Signals
There is a common belief that traffic signals are the answer to all traffic problems at intersections.
In order to develop a broader understanding about what signals will do and what they won't do, here are the answers to the most frequently asked questions regarding traffic signals.
What is the purpose of a traffic signal?
Traffic signals are electronically operated traffic control devices which alternately direct traffic to stop and to proceed. Traffic signals are designed to ensure an orderly flow of traffic, provide an opportunity for pedestrians or vehicles to cross an intersection and help to reduce the number of conflicts between vehicles entering intersections from different directions.
How do traffic signals work?
Traffic responsive controllers change the lights according to the amount of traffic in each direction. These controllers use sensors (inductive loops in the roadway) to detect the number of vehicles and automatically adjust the length of the green time to allow as many vehicles as possible through the intersection before responding to the presence of vehicles on another approach. Although these types of traffic controllers have been in use for many years, a new generation of microcomputer traffic controllers makes the signalized intersection much more efficient, thereby reducing time-consuming delays.
How does ODOT decide whether a traffic signal should be installed on a State Highway?
The Department follows federal guidelines (Manual on Uniform Traffic Control Devices - MUTCD) that establish minimum conditions under which a signal installation should be considered.
The MUTCD manual provides a process for the traffic engineer to follow while investigating conditions and circumstances regarding the installation of a new traffic signal or improve the operation of an existing traffic signal. It contains criteria (warrants) which are used to define the need for, and appropriateness of a particular traffic control device. These warrants are usually expressed in the form of numerical requirements such as the volume of vehicular or pedestrian traffic.
Warrants should be viewed as guidelines, not as absolute values. However, if no warrants are met, a signal will not be installed. Satisfaction of a warrant is not a guarantee that the signal is needed. The warrant analysis process is just one of the tools to be used in determining if a traffic signal is necessary. Engineering judgment should be exercised in making the final determination.
Why does it take so long to get a traffic signal installed once it is approved?
After a traffic engineering study has indicated the need for a signal and the necessary approvals have been obtained, it must be determined how the signal will be funded and who will do the installation.
If the signal is to be installed by a Contractor as a signal project, then it is added to a list of statewide locations which are competing for funds. These funds must be allocated well in advance which results in projects often "waiting" on the list for several years continually competing for funds against other projects which may have a greater need.
Signals can also be installed by local governments in a joint effort with the Ohio Department of Transportation.
Will traffic signals reduce intersection crashes?
Traffic signals do not prevent crashes. Certain types of crashes can be reduced in number or severity by the installation of a signal, while other types will increase. Where signals are used unnecessarily, the most common results are an increase in total crashes, especially rear-end collisions.
Traffic signals are not an answer for every problem intersection. A signal placed at a wrong location can contribute not only to rear-end collisions, but excessive delays, unnecessary travel on alternate routes and more congested traffic flow.
What are the requirements to get a traffic signal installed?
The first step is to perform a warrant analysis. The warrants for a traffic signal are listed in the Ohio Manual of Uniform Traffic Control Devices, section 6C. If the intersection meets any one of these warrants then the next step is to use sound engineering judgement to determine if the signal should be installed. There are cases that because of poor geometry, proximity to existing signals, etc. a location may meet the warrants but not be signalized. If the signal can be installed without negatively impacting other intersections or the traveling public then the signal should be designed and constructed. Per the Ohio Revised Code, the Ohio Department of Transportation can only install and operate signals at public streets. If a private development warrants a traffic signal then the development must enter into an agreement with the Ohio Department of Transportation, pay for the installation of the signal and pay a yearly maintenance/operating fee to the Ohio Department of Transportation.
It should be noted that signals do not cure all traffic problems. Signals increase delay and normally increase rear end and other type of accidents.
How do I request a traffic signal study on a State Highway?
A request for a traffic signal can be initiated from within ODOT, a local government, public official, or a citizen. The request can be for a new traffic signal or for modifications to an existing signal, such as the addition of left-turn phasing.
In some cases, when the request involves private properties rather than public streets, it may be necessary for either the developer or property owner to hire a consultant to conduct the traffic signal study which must be submitted to the appropriate district for review.
To request a Signal Study or to obtain information concerning signals. Contact Julie Cichello at 1-800-276-4188 ext 207-7168.