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Traffic Signals and STOP Signs

Speed Control

Speed TrailerEach year, the City of Norman receives many inquiries about installing STOP signs or traffic signals as a way to reduce speeding.  However, research shows that other measures are often more effective than adding more STOP signs or traffic signals.  The purpose of STOP signs and traffic signals is to assign right-of-way at an intersection, not to control speeding.

Public understanding of the function of STOP signs and traffic signals is one of the most critical elements in reducing speeding and traffic accidents.  The following information explains our policies on intersection traffic controls and the correct use of STOP signs and traffic signals.  In response to these inquiries, the Traffic Division has created an informational brochure related to STOP signs and traffic signals that can be printed and distributed to inquiring citizens.  You can access this informaional brochure by clicking on the following:  STOP Signs and Traffic Signals Brochure.

Installation Policies

MUTCD CoverThe Federal Manual on Uniform Traffic Control Devices (MUTCD) was developed through observation of driver responses to traffic situations.  The MUTCD provides guidelines for installing signs and thus creates uniformity from state to state.  The State of Oklahoma has adopted the MUTCD in Title 47 of the Motor Vehicle and Highway Safety Code.

The MUTCD, which includes policies and guidelines for the installation of STOP signs and traffic signals, has also been adopted by the City of Norman (Section 20-1112 of the City’s Code of Ordinances).  The policies it contains identify specific traffic and pedestrian volumes, accident history, and any unusual conditions which will result in the desired driver response once a traffic control device is installed.  If those conditions are not present, a percentage of the drivers will ignore the traffic control device.

Stop Signs

STOP SignSTOP signs are installed at an intersection only after a careful engineering evaluation of the existing conditions show that the installation of such devices is appropriate.

Our experience has shown that simply improving the intersection visibility by prohibiting parking near the intersection is often more effective in reducing traffic accidents.  This often reduces the need to install more restrictive intersection controls.  Overuse of STOP signs reduces their effectiveness and if installed where not justified, they are largely ignored by drivers who tend to speed up between STOP sign controlled intersections rather than slow down.

Multi-way STOP control can be useful as a safety measure at intersections if certain traffic conditions exist.  Safety concerns associated with mult-way stops include pedestrians, bicyclists, and all road users expecting other road users to stop.  Multi-way STOP control is used where the volume of traffic on all of the intersecting roads is approximately equal.  Request for multi-way STOP control should be forwarded to the City Transportation Engineer or City Traffic Engineer who will authorize a traffic study to determine if the request is warranted.

Traffic Signals

Signal HeadThe City has two types of traffic signals:  fixed time signals and traffic actuated signals. Fixed-time signals are set for average conditions and change at predetermined time intervals.  Traffic actuated signals detect vehicles and adjust the timing to optimize traffic flow at the intersection.

Along some of our major arterials which have several traffic signals spaced at periodic intervals, the traffic signals are usually synchronized to provide coordinated movement along the major street.  Before installing a traffic signal at an intersection, established minimum criteria must be satisfied.

Our review includes an examination of:

  • The amount of vehicular and pedestrian traffic,
  • The need to provide interruption to the major flow for side street vehicles and pedestrians, and 
  • The accident history of the intersection.

Over the past several years, the City of Norman has installed signals at an average of 4-5 per year.  These signals are installed using various funding sources, including your gas tax dollars, state and federal funds, and developer fees.  Costs to install a new traffic signal are approaching $250,000.  Therefore, the installation of new traffic signals must be carefully considered.

Pedestrian Signals

Pedestrian signals have evolved since the 1930s and 1940s.  For years, the version of the pedestrian traffic signals utilizing the "WALK" and "DON'T WALK" messages were in place at various intersections around the City.  Those signals have been replaced wiht the image of the walking man symbolizes the "WALK" interval, and the image of the upraised hand symbolizes the "DON'T WALK" interval.  Now, the "WALK" and "DON'T WALK" messages have been replaced with solid walking man and solid upraised hand images.  In addition, Norman has transitioned to the point that all of our pedestrian signal heads feature the countdown indication.   Below are images of all the aforementioned signal types.

Don't WalkSolid ManCountdown Pedestrian Head

The countdown feature will begin with a large number that is equal to the length of the clearance interval that will count down toward zero.  When zero is reached, the clearance interval has ended and the steady upraised hand is displayed to suggest that pedestrians should no longer enter the intersection.  Research has shown that pedestrians have a better understanding of the clearance interval when associated with the countdown feature.

The latest, ever evolving, innovations in the area of pedestrian equipment are the accessible pedestrian pushbuttons.  Some entities have utilized a device that can be added to traditional pedestrian signal head equipment to give the visually impaired pedestrians a cue that it is safe to cross a given direction.  These devices emit a "chirp" or a "cuckoo" sound depending on which crosswalk is safe to cross.  This can be somewhat difficult for some pedestrians to comprehend exactly which direction is safe to cross.  This technology has further evolved to develop accessible pedestrian pushbuttons which give an audible indication to pedestrians as to which crossing has the right-of-way by giving verbal instructions as to the particular street which may be crossed.  This type of accessible pedestrian pushbutton has become the standard for use at new intersections in Norman.  In addition, projects have spread the technology to other locations.

Traffic Signal Management/Fiber Optics

The City of Norman continues to complete a combination of City funded and Federal Stimulus funded projects to install a fiber optic network for the City, by establishing connections between all city facilities, and to develop an enhanced traffic signal management system.  The combination of these projects has had a number of benefits to citizens and to employees of the City of Norman.  These include, but may not be limited to, the following:

  • Public Works--Real-time access to current street and utility infrastructure, new construction, and work order status.
  • Public Safety--Better able to access and input records data from remote locations ensuring personnel have the most up-to-date information when responding to incidents.
  • Bandwidth improvements--Allows City employees to more efficient in their jobs and devlote more time to customer service.
  • Improved citizen experience accessing City information, business, and video streaming of Council meetings from the Internet.

Fiber optic cable is constructed of glass, and data is transmitted using light spectrum.  Fiber optic cable provides high bandwidth capacity and provides secure, reliable connections.  Fiber optic cable was needed to address a number of the network deficiencies that had been identified by the Information Technology Department of the City.  In addition, the use of fiber optic cable would allow the Traffic Division to upgrade the means of interconnection between traffic signals while allowing flexibility to manage the City’s traffic signals on a powerful, more sophisticated traffic management platform.  The evolution of the numerous fiber optic projects has allowed the City to install more than 50 miles of fiber optic cable.  It provided connectivity to several remote facilities and the incorporation of more than three-fourths of the traffic signals within the City of Norman into a central management system.

The Centracs system was launched in Norman in November 2009.  At the time it was launched, Norman joined a handful of municipalities that had successfully launched the system.  With the Centracs system, Norman is able to take advantage of the traffic signal management and control that the system affords.  One of the best features of the Centracs system is that we are sent alerts when certain field conditions happen.  One of the best examples is when an intersection that is part of the Centracs system goes into flash.  Centracs will send us an e-mail and a text message to whomever the City designates when a signal goes into flash.  This allows us to get technicians into the field more quickly to respond to these types of events.  As more and more of our signals are added to Centracs, we rely less and less on law enforcement or citizen calls to report a signal in flash.  This feature allows us to cut the response times significantly.  Strategic planning is necessary to make sure future fiber corridors are identified to make sure that new signals can be brought into the Centracs system as the opportunities to do so become apparent in the future.