I think that currently, individuals abuse the mechanic job for easy repairs. What I suggest is to limit each repair shop to 3 mechanics. The owner + 2 hired mechanics. This will limit the amount of mechanics on the server and also allow for more competition among all of the mechanics for things like upgrades and roadside repairs, by limiting the choices that people have for these things. As it currently sits most mechanics do not respond to roadside repairs nor tow requests.
To see this working, head to your live site.
We are working on addressing this situation.
What might help to is to incentivize tows, maybe get a game mechanic to allow police to tag vehicles for tows that would give the driver a couple hundred dollars per tow