Use Maps to walk without using streets

I'm going to an event where there will be hundreds of buses parked in a large stadium parking lot, think disneyworld size. I'd like to use Maps to guide me back to my bus, but I can't figure out how to use it in "walk" mode without it trying to force me onto the closest streets, which generally results in a much longer route. So what I want to do is set a location for the bus, and then from any location up to 1/2 mile away, be able to have it walk me on a straight line to the bus, without forcing me to use any local streets. How do I do that? This would also be useful in the forest preserve, if I just wanted it to walk me straight home without being taken off onto the closest local street.

tnx