Eventually, the upgrades could do away entirely with the red, yellow and green lights of today, ceding control to driverless cars. Henry Liu, a civil engineering professor who is leading a study ...

Eventually, the upgrades could do away entirely with the red, yellow and green lights of today, ceding control to driverless cars. Henry Liu, a civil engineering professor who is leading a study ...

Potts’s prototype cost $47 to construct and featured three lights: red, yellow and green. The yellow light signalled drivers to slow down and prepare to stop. Potts’s invention, which became ...