A 12-mile stretch of highway in California's Central Valley that has been the scene of deadly car crashes due to thick fog now has a wireless warning system to alert drivers.
The system, dubbed the Fog Pilot project, was installed in December for US$12 million to combine a WiMax network with fog sensors and electronic highway signs, according to the California Highway Patrol and California Department of Transportation.
The system "is a tool we use to send messages to drivers right away that dense fog is ahead, and that they should slow down to a certain speed," said Highway Patrol Officer Matt Radke, a spokesman for the central division, in a telephone interview Tuesday.
The stretch of State Route 99 runs through a valley located between the Sierra Nevada Mountains, which tend to trap fog, Radke said. Large farms in the area sometimes burn off fields, which can generate thick smoke, he said.
The area is notorious for causing accidents, some of which have been deadly, including an 86-car collision in November 2007, Radke said. Drivers entering a fog zone slow down dramatically but can be struck from behind by cars still moving at a faster speed. Radke estimated there have been more than 50 multi-car crashes due to fog in the 12-mile stretch since 2002.
The most immediate impact of the warning system has been to reduce the need for the Highway Patrol to organize police cruisers into pace cars, which move down a stretch of highway at a slower speed to force the traffic behind them to slow down, Radke said. "We're not having to pace as much on that stretch," he said.
The system integrates many technologies, including 21 weather detection stations, microwave vehicle motion detectors every quarter mile, visibility sensors, closed circuit-television cameras and electronic warning signs with changeable messages every half mile, according to Proxim Wireless Corp., one of the equipment providers.
The weather and traffic data moves over WiMax, a high-speed wireless network, through Proxim radios and is managed centrally by Proxim, the company said. ICx Technologies provided traffic sensors and transportation management software, and Moonblink Communications acted as a wireless integrator on the project.
Radke said the fog information can be turned into a warning to motorists in less than 30 seconds. But he added that the warning system is just another tool for preventing accidents.
"People still have to pay attention to the signs and reduce their speeds," nor should they be using a mobile phone while driving or "eating dinner or breakfast at the wheel," he said. "That happens."