I'm just back from the "ITS World Congress" an annual meeting of people working on "Intelligent Transportation Systems" which means all sorts of applications of computers and networking to transportation, particularly cars. A whole bunch of stuff gets covered there, including traffic monitoring and management, toll collection, transit operations etc. but what's of interest to robocar enthusiasts is what goes into cars and streets. People started networking cars with systems like OnStar, now known in the generic sense as "telematics" but things have grown since then.
The big effort involves putting digital radios into cars. The radio system, known by names like 802.11p, WAVE and DSRC involves an 802.11 derived protocol in a new dedicated band at 5.9ghz. The goal is a protocol suitable for safety applications, with super-fast connections and reliable data. Once the radios in the car, the car will be able to use it to talk to other cars (known as V2V) or to infrastructure facilities such as traffic lights (known as V2I.) The initial planned figured that the V2I services would give you internet in your car, but the reality is that 4G cellular networks have taken over that part of the value chain.
Coming up with value for V2V is a tricky proposition. Since you can only talk to cars very close to you, it's not a reliable way to talk with any particular car. Relaying through the wide area network is best for that unless you need lots of bandwidth or really low latency. There's not much that needs lots of bandwidth, but safety applications do demand both low latency and a robust system that doesn't depend on infrastructure.
The current approach to safety applications is to have equipped cars transmit status information. Formerly called a "here I am" this is a broadcast of location, direction, speed and signals like brake lights, turn signals etc. If somebody else's car is transmitting that, your car can detect their presence, even if you can't see them. This lets your car detect and warn about things like:
- The car 2 or 3 in front of you, hidden by the truck in front of you, that has hit the brakes or stalled
- People in your blind spot, or who are coming up on you really fast when your're about to change lanes
- Hidden cars coming up when you want to turn left, or want to pass on a rural highway
- Cars about to run red lights or blow stop signs at an intersection you're about to go through
- Privacy is a big issue. The boxes change their ID every minute so you can't track a car over a long distance unless you can follow it over every segment, but is that enough? They say a law is needed so the police don't use the speed broadcast to ticket you, but will it stay that way?
It turns out that intersection collisions are a large fraction of crashes, so there's a big win there, if you can do it. The problem is one of critical mass. Installed in just a few cars, such a system is extremely unlikely to provide aid. For things like blindspot detection, existing systems that use cameras or radars are far better because they see all cars, not just those with radios. Even with 10% penetration, there's only a 1% chance any given collision could be prevented with the system, though it's a 10% chance for the people who seek out the system. (Sadly, those who seek out fancy safety systems are probably less likely to be the ones blowing through red lights, and indeed another feature of the system -- getting data from traffic lights -- already can do a lot to stop an equipped car from going through a red light by mistake.)