Add vehicle maintenance to this. If you don't already have them cleaning and organizing trucks, you should have them doing so.

Showing up at a job with a dirty truck (this IS a big one), that may not have the little extras needed, is not a good idea.

Truck need a full service? Sure it does. Nothing like sitting on the side of the road due do a truck that wasn't taken care of.

Yes, they can and should wash their truck. It's not something demeaning, it's just part of the job. Keeping up the image of a professional company, and it's staff. Besides, on a steamy hot summer day, this can be a good way to cool off AND get paid for it.