Rakha and his colleagues at VTTI came up with yellow times to account for various driver populations in extensive testing on the Virginia Department of Transportation’s Virginia Smart Road. A certain amount in yellow time that will result in 95 percent of the drivers not being caught in the dilemma zone and only potentially 5 percent being caught in the dilemma zone. For a result of 99 percent not being caught in the dilemma zone, a longer yellow time is required.
“If you’re designing the yellow times in Florida, where the majority of the drivers are older, you have to come up with a different yellow time than if you’re designing yellow times for here in Blacksburg, Virginia where the population is younger, and the majority of the population is students,” said Rakha.
Although none of the possible solutions Rakha mentioned are likely to occur anytime soon, there are several distinct ones that could provide drivers with advance warning, more time to react, and better decision-making options.
In-car warning systems – “Potentially you could have a warning in your vehicle that basically recognizes your age, gender, and can warn you before the yellow light comes on, to give you that extra time you need to take your action,” Rakha said.
In a paper sent to the Department of Transportation, Rakha proposed that automakers could possibly create such a system. But it would have to be more than just a forward-collision warning system. It would have to be in communication with the traffic signal controller, vehicle-to-infrastructure (V2I) and infrastructure-to-vehicle (I2V).
Department of Transportation vehicle-to-vehicle (V2V) programEnlarge Photo
V2I and I2V
“The infrastructure would inform the vehicle that the light will be turning yellow in, say 10 seconds,” said Rakha. “When you’re approaching the traffic light, you’re going to get some kind of communication, and then the vehicle can react. It could be some kind of in-car driver display, providing a countdown to yellow to alert the driver to start slowing down, or giving the driver the actual decision by automatically applying the brakes. Of course, sensors would be required to measure wet and dry conditions.”
According to Rakha, his group’s proposed approach could be integrated within the Connected Vehicle Research program, which can gather information on the driver, the subject vehicle, and surrounding traffic conditions to execute safe and customizable change interval in-vehicle warnings.
Flashing yellow - Drivers approaching a high-speed intersection need a much longer yellow. A flashing yellow informs the driver earlier that it’s going to be yellow so that he can make the decision. “If I’m upstream of this, I should stop. If I’ve passed that flashing yellow, then I should run,” said Rakha.
This is something Rakha’s group suggested in their report to the DOT. Germany, for example, has a flashing yellow on the traffic lights a couple of seconds before the yellow comes on.
Yellow line on roadway
“We also proposed to the DOT to draw a yellow line on the roadway,” Rakha said. “If the traffic signal turns yellow when you’re upstream of that line, you should stop. If you’re downstream of that line, you should continue at present speed through the intersection. You should be able to proceed without running a red light.”