All good comments, have any of you actually been in a Prius? It's keyless, the key is in your pocket (on the latest model), so you can't 'switch off the engine', I have no idea what would happen if you pressed the 'START' button whilst driving - probably nothing. Also, there's no handbrake, only a footbrake (next to the 'foot' brake ), and a P button (which again, probably does nothing when driving). Plus, they're auto and the gearbox is electric, you have to hold it over N for a few seconds before it disengages D.
Basically it's all very confusing and not straight forward to slow down if the brakes fail or throttle sticks or whatever it is with Toyotas today.