[WkndTriathlete]

The tag is to indicate that the vehicle has paid the appropriate taxes for using the roads. If the tax on the vehicle is not paid then it should not be used on the roads.

Without the tag there is no way to enforce that without the police having to manually enter the plate number for every vehicle they see. Hence the tag: if the police see a vehicle without an up-to-date tag applied it is not legally allowed to use the roads since the owner hasn't paid to keep the roads maintained from the wear incurred by the vehicle while driving on them.

There is an argument to be made that the police could simply use a system that reads license plates up and checks the information automatically, but there are so many 4th amendment abuses/workarounds that the police already use it's hard to imagine much public support for such a system.

[ezfe]

While I have no problem with the tag, your claim is false:

> Without the tag there is no way to enforce that without the police having to manually enter the plate number for every vehicle they see.

Police have automatic systems that scan vehicles. I was pulled over once due to an inconsistency in my vehicle registration data (not anything visible on the plate/exterior) because the computer in the police vehicle flagged my car and they decided to follow up on it.

In my case, it was just a quirk of the vehicle owner being unlicensed to drive and there was no violation - but the system correlated the DMV registration details and license status of the owner and flagged the car.

[fps]

fast accurate plate scanners are relatively new. At most, only on police cars for the past 10 or so years. Many police cars still don't have them, only dedicated highway patrol cars. The sticker system has been in place for over 80 years. Systems that work, that are are generally not difficult to implement stick around past when they're technologically outdated.