So what is the Dilemma Zone?Hesham Rakha, director of the Center for Sustainable Mobility at the Virginia Tech Transportation Institute, defines the Dilemma Zone as the place where a driver has no feasible choice. He can neither stop nor continue through the intersection before the light changes to red. The standard yellow time is 4.2 seconds on a 45 mph road. On faster roads, the length is longer. The formula is based on two assumptions: It takes the average driver one second to perceive and react to a yellow light and 3.2 seconds to safely stop the car. However, research released last fall found that 4.2 seconds is just not enough time in many situations. Rakha and fellow researchers determined that perceiving and reacting to a light change takes a bit longer than one second and deceleration times are much longer than standard yellow light times. Poor road conditions slow both reaction and stop times. Data showed that 43 percent of drivers who crossed the stop line during a yellow light were unable to clear the intersection.
A warning light for the caution lightA longer yellow light isn't necessarily the answer, Rakha says.
"You could design the yellow time so that 90 percent of drivers - or 95 percent -- are not caught in the dilemma zone. But the higher you go, the longer the yellow time is, which increases the time cross traffic is stopped," he says.That would not only increase pollution, Rakha notes, but also the risk of more drivers taking chances to avoid a long light. Other solutions the group suggests could include warning lights that make drivers aware that a green light is about to change, or an in-dash display that communicates with the traffic lights and makes the decision for the driver. Until the day those smarter yellow lights appear, drivers must make their own choices. The safest one is almost always to stop.
What is the law?Laws regarding yellow lights vary by state, but in general there are two schools of thought. Many states use a "touchdown" rule. This means if the car breaks the plane of the white line at the intersection before the light turns red, the driver is allowed to clear the intersection. Other state laws are more vague. The wording goes something like this: Traffic facing a yellow signal shall stop before entering the intersection unless so close that a stop may not be safely made. These laws are bit harder to enforce. A Wisconsin police officer on an Officer.com forum discusses enforcement issues. "The yellow light violation can be enforced, but it has to be pretty blatant. I've written and successfully argued it in court, but I had video showing the vehicle was clearly able to stop, but sped up to make the light." In 24 states and the District of Columbia, red light cameras take enforcement to the next level, penalizing any driver who crosses the white line while the light is red, even by only a foot or two.
A study by the Insurance Institute for Highway Safety (IIHS) looked at 14 cities using red light cameras and found that the combined per capita rate of fatal red light accidents decreased by 35 percent. On the flip side, The Federal Highway Administration and Virginia Transportation Research Council found that red light cameras probably caused more rear-end crashes.