Soon, cars will be able to communicate with each other. They'll warn their drivers of suddenly slowing traffic, sharp turns, changing stoplights and other hazards. Cars might automatically reduce speed. The European Union recently designated a radio frequency for this purpose. The U.S. and Japan previously reserved the same frequency. The idea is to use a wireless local area network (W-LAN) similar to Wi-Fi hotspots found in coffee shops. When one vehicle, for instance, skids on an icy spot, it will automatically send a bulletin to cars within range, says the Car 2 Car Communication Consortium, a group of vehicle makers and suppliers. Like a digital version of citizen band radio, vehicles travelling in the opposite direction will receive and rebroadcast the alert to cars approaching the hazard. Computer engineers call this an ad hoc network. No public-financed infrastructure is required, but government-controlled transceivers can be a part of the system. Some fear that it could be used to spy on motorists. There's no word on when inter-vehicle communications will see mass production.