Is sitting in traffic as inevitable as death and taxes？ Perhaps not. Many countries now ha

ve dedicated traffic-monitoring centres linked to networks of cameras and sensors. Throw in traffic-spotting aircraft, accident reports and the known positions of buses fitted with satellite-positioning gear, and it is possible to see exactly what is happening on the roads. Drivers could switch from busy to quiet routes and avoid congestion-if only they had access to this information.

And now they do. Systems such as the Traffic Message Channel and the Vehicle Information and Communication System (VICS), in Europe and Japan respectively, pipe data from traffic centres into in-car navigation systems via FM radio signals. Drivers can see where the traffic is and try to avoid it. Honda, a Japanese carmaker, even combines VICS data with position data from 150,000 vehicles belonging to members of its Premium Club so that they can choose the fastest lane on a congested road, says David Schrier of ABI Research, a consultancy.

Meanwhile ITIS, a British company, is one of several firms experimenting with mobile-phone signals to monitor traffic on roads that lack sensors or cameras. Its software hooks into a mobile operator's network and uses a statistical approach to deduce traffic speeds as phones are "handed off" from one cell tower to another. The data must be cleaned up to exclude pedestrians and cyclists, but this idea has great potential, says Mr. Schrier.

Another way to dodge traffic is to predict where and when it will form. In Redmond, Washing ton, at the headquarters of Microsoft, employees have been testing a traffic-prediction system called JamBayes. Users register their route preferences and then receive alerts, by e-mail or text message, warning them of impending traffic jam. JamBayes uses a technique called Bayesian modeling to combine real-time traffic data with historical trends, weather information and a list of calendar events such as holidays. Eric Horvitz of Microsoft, who developed the system, says it is accurate 75% of the time, and 3, 000 employees use it daily.

A system called Beat-the-Traffic, developed by Triangle Software of Campbell, California, with funding from the National Science Foundation, goes further. It not only warns drivers of impending traffic but also suggests an alternative route via e-mail or text message. Andre Gueziec, the firm's boss, thinks traffic forecasts will become as prevalent as weather forecasts. Indeed, in June, KXTV News 10, a TV station in Sacramento, California, began showing Triangle's traffic forecasts for the coming week.

To know what is exactly happening on the roads, we don't need to

A．dispatch aircraft to spot the traffic.

B．guarantee drivers have access to the information system.

C．obtain related reports of accident.

D．collect data of the positions of buses.