The rules change depending on where you are. Down here, it's state-by-state...it may be the same where you are. You can find this kind of information either online, or by checking in with your vehicle registration service. They may not know off the top of their heads, but they'll be able to point you in the right direction to find out the specifics. It would be good to keep a copy of the statutes on-hand when you go to get your inspection.
If it's worth doing, then it's worth over
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The build, the gear, and the mileage: The Wasteland Survival Guide