Roadguy spent a good chunk of this past week thinking about license plates. It all started with a question from alert reader Brian, who perhaps contemplates the plates in front of him whenever he's stuck in traffic:

What determines when Minnesota stops issuing license plates in the current ABC 123 format and switches to 123 ABC? The state has been alternating between those two schemes for ages, but there has never been any apparent rhyme or reason as to when they switch.

In fact, plates issued have never actually reached the end of the alphabet; the fact that we're now seeing plates starting with X is downright surprising, considering previous passes through the alphabet have always ended several letters earlier....

Brian is not entirely alone in his interest in this topic. A few months ago, Roadguy heard from alert reader Jay, who spotted an "X" plate and wondered why the state had skipped W. Then there was the friend of Roadguy who wondered why plates must be replaced every seven years regardless of condition.

Roadguy clearly needed to get up to speed on license plates, so he called up our friends at the Department of Public Safety, and here's what he learned.

Alphabetically speaking

First, the letters-numbers thing: State officials say it takes about a decade to go through the letters-first series before they switch to the numbers-first format. But sometimes there are interruptions:

About 1996 we changed from steel to aluminum plates, and we started over with ABC at that time to distinguish between the types of plates.

And there's a reason Brian and Jay are seeing more X plates, which aren't always used on ordinary vehicles: The state folks are planning another "manufacturing change," and they don't want to switch to the numbers-first format until they do that. So X, which is normally used for a restricted class, has been pressed into regular service.

The "manufacturing change" is a plan to switch from plates with raised letters to new, flat plates that are produced digitally. Some "support our troops" and Critical Habitat plates are already made this way.

Recycle, don't reuse

As for letting vehicle owners keep their plates longer, "the seven-year replacement policy is a statutory requirement," says public safety spokeswoman Kris Chapin. "There is a five-year warranty on the reflective material, so plates will continue to need to be replaced."

The next-generation plates will be aluminum, like the current ones, so people concerned about waste can recycle them. ("Not everyone nails them to the garage walls for 30 years," Chapin noted, causing Roadguy to wonder whether she'd been peeking in his garage.)

But before you dump your plates in with your empty Fresca cans, check whether your recycler will accept them. They're OK in Minneapolis, but will be rejected as "scrap metal" in St. Paul and other cities served by Eureka Recycling.

If you can put them out curbside, the plates should be "bent and creased, or otherwise defaced," so someone doesn't pick them out of the bin and try something nefarious.

You also can turn your old plates back in where you got them, and they'll be recycled.

The letter W is not your friend

And what about W and beyond?

Normally, we don't go past W because of the possibility of confusion with the "restricted" and commercial class vehicles that are W, X and Y.

Z is held in reserve for other special uses such as the disability classification.

Plates starting with W, it turns out, can be serious business:

The W is used ... to identify a plate that is subject to impoundment -- i.e. if they catch you doing the same thing you got the plates for, they'll take your car to the impound lot until you do whatever is required to get it back.

Offenses that can earn you a W plate include such things as drunken driving, driving without insurance or a license, and not paying a large number of parking tickets.

Roadguy has decided that, when he sees plates that start with W, the W reminds him to be "wary." • 612-673-4491