US Proposes Optional Blue-Green Lights for Self-Driving Cars

The US car safety regulator, NHTSA, has proposed an optional blue-green light for self-driving vehicles. Carmakers that add it would follow national rules for its color, brightness and position, so it looks the same on every compliant car.

In my view, the light's value depends on how many cars use it, since an optional signal helps only where it appears.