Route 9 is an old two-lane highway that cuts across Massachusetts from Boston in the east to Pittsfield in the west. Near the small city of Northampton,the highway crosses the wide Connecticut River.The Calvin Coolidge Memorial Bridge, named after the president who once served as Northampton's mayor, is a major regional traffic link.When the state began a long-delayed and still-ongoing reconstruction of the bridge in the summer of 2001, traffic jams stretched for kilometers into the bucolic New England countryside.

In a project aimed at alleviating drivers' frustration, the University of Massachusetts Transportation Center, located in nearby Amherst, installed eight shoe-size digital surveillance cameras along the roads leading to the bridge. Six are mounted on utility poles and the roofs of local businesses. Made by Axis Communications in Sweden, they are connected to dial-up modems and transmit images of the roadway before them to a Web page, which commuters can check for congestion before tackling the road. According to Dan Dulaski, the system's technical manager, running the entire webcam system—power, phone, and Internet fees—costs just $600 a month. The other two cameras in the Coolidge Bridge project are a little less routine. Built by Computer Recognition Systems in Wokingham, England, with high-quality lenses and fast shutter speeds (1/10,000 second), they are designed to photograph every car and truck that passes by. Located eight kilometers apart, at the ends of the zone of maximum traffic congestion, the two cameras send vehicle images to attached computers, which use special character-recognition software to decipher vehicle license plates. The license data go to a server at the company's U.S. office in Cambridge, MA, about 130 kilometers away. As each license plate passes the second camera,the server ascertains the time difference between the two readings. The average of the travel durations of all successfully matched vehicles defines the likely travel time for crossing the bridge at any given moment, and that information is posted on the traffic watch Web page