Check out the DSRC (Dedicated Short Range Communications) standard. Also labeled WAVE (Wireless Access in Vehicular Environments) and 802.11p with IEEE 1609. Basically a vehicle status message is transmitted multiple times a second and vehicles within a few hundred meters can receive these transmissions and act on that info. So when someone tries to turn left in front of a motorcycle that is transmitting it's vehicle status (location, velocity, size) the corresponding receiver on the vehicle will compute the collision course and put out a big warning to the vehicle. Once the system gets reliable and secure enough perhaps the vehicle will even do things like put on the brakes or prevent someone from running a deep red light.
The National Highway Transportation Administration is expected to decide any day now if it will be required in vehicles starting in a few years. Also systems are starting to crop up that are small, perhaps even integrated directly into smartphones someday.