Note that in current gas/electric hybrids, the concept of "started" loses most of its meaning. The system as a whole can be "on" or "off", but doesn't intrinsic

Note that in current gas/electric hybrids, the concept of "started" loses most of its meaning. The system as a whole can be "on" or "off", but doesn't intrinsically make any sound that distinguishes the two states. The gas engine subsystem will get turned on and off at the whim of the controller; if the engine is up to operating temperature and the battery's charge level isn't too low, the controller will turn off the engine whenever its power isn't needed (stopped at a stoplight, driving very slowly, coasting down a hill, etc.). On some models, it's also possible to press a button to tell the system "delay starting the gas engine as long as possible". Hence the concerns about hybrids "sneaking up" on pedestrians.