Researchers at the Texas Transportation Institute (TTI) have developed a new system to improve the safety at high-speed rural intersections by reducing red-light violations and sudden stops by up to 70 percent.
Drivers approaching a high-speed rural intersection with a green signal that suddenly changes to yellow have a split second to make an important decision: Is it safer to decrease speed quickly and stop, or continue driving through the intersection? This period is referred to as the “dilemma zone,” and the wrong decision may result in a fatality or major injury.
“Our objective is to prevent the light changing from yellow to red when vehicles are approaching the intersection,” says Jim Bonneson, TTI supervisor of the project funded by the Texas Department of Transportation (TxDOT). “The dilemma zone can be a problem if a driver misjudges the light and has to stop suddenly or ends up in the intersection after the red. We’re trying to prevent these events from happening.” The new system, which researchers call a Detection Control System (D-CS), involves three components:
- Detectors are located in each lane of the roadway approximately 1,000 feet away from the intersection. When the drivers travel over the detector, a signal is sent to controller cabinet.
- After receiving the signal, the system records the vehicle size, speed and lane number. The information is processed, and the system decides what happens next.
- Then, either the green light ends or it stays green until the vehicle passes through depending on the signal from the system.
The best time to end the green light, experts say, is when there are no vehicles approaching from either direction. After the computer waits 30 to 40 seconds and does not detect this condition, it is likely that traffic volumes are too high to find the optimal time, and the system will allow the light to change when a maximum of one car (but not a truck) is in the dilemma zone. Traditional traffic controllers provide green lights on a pre-programmed time schedule and often turn yellow when drivers are in the dilemma zone.
Currently, the system has been installed at Highway 6/Loop 340 and FM 3400 near Waco. TTI and TxDOT will install additional systems around Texas over the next two years:
- Near Gainesville at US 82 & Weber Drive and at US 82 & FM 3092
- Near Waco at US 84 & Williams Road
- Northwest of Galveston at SH 6 & Jackson Street and at SH 6 & Tower Road
- Near San Antonio at US 281 & Borgfield Drive and at. US 87 & FM 1628
Officials say that more systems will be installed as funding allows.