if what you are intending to do was be fair to -all- then everyone must come to the shop on their own transportation and leave from the shop in company vehicles and return company vehicles to the shop each night otherwise is not fair to whomever lives closest. You then run into being responsible for personal property in the vans overnight, as I am sure you recognize.
If the goal is to set policies and procedures for a long term company that may grow, then you must put it in writing so that Everyone understands what to expect.
It seems to me that this should be more of an indivual wage-benifit negioation than a general "1 rule fits all" kind of thing.
Do you pay every road tech the same hourly rate or is there room to negiotate salary? One of the things I demand from my employer in "pre-employment negotiation" is absolute confidence about how much I earn with relation to my coworkers. Do you have a situation where other employees are aware of how much each other earns?
I think I would also point out that as others have noted above, the truth is that it is as much or more a benefit to the company (more than any other enity including the tech) to have the tech start first thing inroute to a customer as it is for the tech,as such it is a mistake in the long run to lock yourself into thinking it is a benefit for the tech.