The traffic density data collected by the systems is also incorporated into digital road maps, which drivers can download onto their smartphones or navigation systems in order to find the quickest routes out of town. In an emergency, the system can centrally control all traffic lights.

Comparative tests with procedures that calculate traffic density on the basis of stationary toll tag readers, such as those used for congestion charges, have shown that the Siemens system provides reliable data even if only a few drivers have their cell phones switched on.

The project is being conducted in Harris County, Texas, which includes the greater Houston area. With its more than four million inhabitants, Harris County is one of the most populous counties in the United States. When Hurricane Ike hit Texas in September 2008, the county was faced with the challenging task of evacuating thousands of residents in what was the third-most costly disaster in US history. Intelligent traffic technology will help to make such emergency situations less challenging in the future, according to Siemens.

The system has now been installed at 400 intersections in Harris County. The organizers plan to standardize communication between emergency vehicles and the infrastructure so that traffic lights will automatically turn green whenever a fire truck, police car, or ambulance approaches.

Along with Bluetooth, the installations include GPS and Dedicated Short Range Communications (DSRC) antennas. Emergency vehicle on-board equipment sends the GPS location via DSRC to a software application in the controller indicating that the approach vehicle should receive priority. The application is able to read approach direction and speed allowing for the signal timing to initiate a green regardless of the oncoming speed of the approaching emergency vehicle. This means the priority can be applied specifically to the route required, whether going straight through the intersection or turning left.

The system could even coordinate traffic lights if several emergency vehicles approach an intersection simultaneously. Siemens is currently developing such a system for testing by the US Department of Transportation.

Intelligent traffic management is not only useful in emergencies, however; it also improves everyday traffic flows, reduces noise, the number of accidents and traffic jams, and benefits the environment. In cooperation with BMW, Siemens demonstrated that communication between traffic lights and engine control systems can reduce fuel consumption by shutting off the engine just before a traffic light turns red. Intelligent traffic management is one of the key areas being addressed by Siemens’ new Infrastructure & Cities Sector, which will begin operating on 1 October.