Self-driving cars are only as good as the sensors they use to detect the world around them. But the University of Michigan believes sensors alone aren't good enough. They want self-driving cars communicating with each other directly and have carried out the tests to prove why that's better.

A University of Michigan-led public-private partnership created the 32-acre Mcity test track, which allows for new driving technology to be tested away from public roads. In this case the self-driving cars were equipped with Dedicated Short Range Communications (DSRC), allowing the vehicles to transmit up to 10 messages per second to each other over a short range.

Those messages contain all the relevant information about a vehicle's state, and importantly, they do not require line-of-sight like many of the other sensors on these cars do. So in a scenario where there is a blind bend, or a sudden hard application of breaks, DSRC can convey that information to all vehicles nearby even before they are registered visually.

Testing such a system thoroughly requires a lot of cars in order to recreate very busy roads. The university overcame that problem with augmented reality (AR), which allowed them to put as many virtual cars as they liked on the Mcity test track.

Using AR also allowed Mcity Director Huei Peng, who is the Roger L. McCarthy Professor of Mechanical Engineering, to tap into existing real-world driving data (25 million miles of it). So with very few real cars, Mcity is still able to test as if driving on real roads in all conditions and possible scenarios.

Ultimately what Peng and his team found is that by adding vehicle-to-vehicle communication self-driving cars become safer.