Cities install traffic lights with sensors and an internet connection so that it can be controlled from the city traffic management HQ. There are dozens of professionals in front of giant screens, and a supercomputer at their disposal. Could that information be sent directly to cars?
No, instead we cram a computer and a camera into every car and hope it can find the right pixels on the picture in fog and rain.
Smart approach would be to invest in infrastructure - standard location beacons that tell cars exactly where they are and what is ahead, wireless communication between cars so they know locations and bearing of every vehicle within a square mile, wireless tags could be installed on all bikes and cycles, etc. We have an entire department for traffic management in each city that could suggest a route to every car?
We already installed speed cameras, number plate recognition, pedestrian counting, we have vehicle sensing sensors inside the road that count and weigh cars, and none of this information is being used. If cloud computing makes sence for crappy apps, then it definitely makes sence to assist cars.