I was sitting outside, eating my lunch the other day, and a small bus (you know, one of the short ones) pulled up to the sandwich shop I was eating at. I noticed that the driver got out of the bus, ordered her food and waited for the roughly 10 minutes until the she received her sandwich and then proceeded back to the bus and ate her sandwich, all the while the bus was still idling the entire time!
My natural assumption is that this is a HUGE waste of gas, and thus prompted the thought "Why?!". So my question is this, are there any distinct advantages to idling a vehicle over shutting it off, and then starting it back up again? If so, is there a general 'time limit' for idling the vehicle?