if what you are intending to do was be fair to all underline all then everyone must come to the shop on their own transportation and leave from the shop in company vehicles in return company vehicles to the shop each night otherwise is not fair to whomever lives closest. 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.
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?