The chaotic city of Houston paves the future of driverless delivery

On the muggy streets of suburban Houston, amid ­McMansions, bright green lawns and stately oak trees, a futuristic race is quietly afoot.

The contestants are not people but Toyota Priuses outfitted with an array of sophisticated sensors. Despite fierce competition and unending pressure to perform, the nearly silent electric vehicles do not speed. They move cautiously, rigorously following traffic laws and never topping 25 mph.