I am envisioning a system of smart roads/highways/freeways and connected smart cars. The traffic signal system is connected with cars to control speed limits, red light stops, stop sign stops etc. Smart cars will connect to roads, city street, freeways on selected route. Traffic light signals will send signals to cars and control the traffic flow. Everything is automated via traffic signal system. This will reduce any chance of human errors. Just like cell phone acquire signals from cell phone towers and switch towers based on locations. In this century when we are thinking about colonizing Mars, connecting everyone on earth. This use of technology will save many from life preemption. Certain standards for street length and connectivity may be required for this system to be fully effective. And off-course need to have this as a required feature just like smog test and back lights.