A Honda Motor Co. Acura RLX sedan demonstrated an unusual way to tow another car last week: the vehicles were not physically attached. The second car drove itself, following instructions beamed over by the first in a feat of technology that indicates a new stage in automation is happening faster than many expected.

Systems that enable vehicles to communicate with each other have been developed in recent years in parallel with features that enable cars to drive themselves. Manufacturers and suppliers in Japan and overseas now are putting the two together in novel ways, with broad implications for vehicle safety and convenience.

Honda, General Motors Co. and other automakers are working with traditional suppliers and startup firms. Tech giants Google Inc., with its pioneering work on driverless cars, and Apple Inc., which is working with automakers to embed greater connectivity in their cars, are accelerating the change.