In the past, cruise control was an option. It was a separate device or circuit added to the car upon purchase. Nowadays, I think it’s actually part of the car’s CPU.
Recently, I read a discussion about acceleration. Which saves fuel, slowly attaining speed, or rapid acceleration to get to speed quickly.
Could the cruise control be hacked (or redesigned) to allow for an automatic acceleration? When the light went green, you would flick a paddle, and the car would accelerate from zero to the speed required, using the various sensors to regulate for fuel usage. When you flicked it again, the car would maintain the speed in cruise. Everything would be overridden by the pedal or brake.