Solving Dilemma Zones

I’m intrigued by the technology described in this article to reduce so-called “dilemma zones” — i.e., the moment when a light is turning yellow and an approaching driver is caught in a dilemma: They’re going to fast to stop yet they may still catch some of the red.

The report notes: “Indecision within the dilemma zone contributes to crashes at high-speed intersections. If a car is traveling at a steady speed or accelerating in that zone, the sensor relays that information to the traffic light, which will give the car a longer green light and time to clear the intersection.

My only question here is the “human factor.” If drivers know they are to be rewarded by gunning it towards the intersection, may not that also pose all kinds of risks? If a steady stream of fast vehicles keeps getting picked up by the sensor, adding time to the signal, when does the signal ever decide to change?

This entry was posted on Monday, October 6th, 2008 at 10:14 am and is filed under Drivers, Traffic Engineering, Traffic Gadgets. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

4 Responses to “Solving Dilemma Zones”

  1. Mark Hunter Says:

    The only solution may be a double red light for two or three seconds. Of course, as you say, if people know this, then some may take advantage.

  2. Peter Koonce Says:

    There is an upcoming study that will be conducted by the National Cooperative Highway Research Program on the issue of setting Yellow and All Red Times. I agree that if drivers knew they may abuse the system. A study cited in the Signal Timing Manual ( by Souleyrette, R. R., O’Brien, M. M., McDonald, T., Preston, H., and Storm, R., “Effectiveness of All-Red Clearance Interval on Intersection Crashes”, Center for Transportation Research and Education, Iowa State University, Minnesota Department of Transportation, MN/RC-2004-26,, May 2004, states that lengthening the time of a red indication has no long term improvement on safety because of drivers learning the system.

  3. Jeff McMullen Says:

    Just for the record. The dilemma zone is influence by more than the Yellow or Red time. It is mainly the result of detector placement,the minimum gap timing, vehicle speed and intersection congestion. Actually, Red timing has nothing to do with the dilemma zone. If a driver has made the decision to run the red, he is already past the dilemma zone.

    The statement above is born not out of pure research or studies but more than 20 years of field experience.

  4. MALLEN Says:

    A dilemma Zone can be prevented by simply increasing the yellow light time, as usual timings are around 3 seconds, but if this time is increased to 4 seconds it would allow extra time for those who are in the orginal dilemma zone, to pass safely through the intersection.

    This option would also create a negative dilemma zone calculation, which imply’s no dilemma zone is present, an overlap of the to situations…. All Positive.

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