A safety device for vehicles. The device inhibits use of communication devices that run the risk of distracting a driver/operator while the vehicle is in motion. Several techniques for inhibiting use are described which can be used individually or in a complementary combinations. In one technique, a rapidly varying signal level is created local to the communication device. The variations exceed the operational limits of the system, thereby inhibiting communications. The device may be in a constant-on mode, unless it detects an attempt to make a communication classified as appropriate. Such a device may inhibit short messages, such as “text” messages and may also allow or, in some embodiments, place emergency calls.