If you’re bored and , chances are you’ve probably looked around at the vehicles around you, looking for something, anything to ease the pain. As you play Miley Cyrus’ Party In The USA while you inch forward, you’ve probably spotted something off to the side on a slow-moving truck. The wheels on its trailer have little strips slowly rotating, drawing your attention in. What are those for?

Take a drive around Chicago, its suburbs and rural Illinois, and you’re bound to see the that Jason talked about yesterday. Weirdly, you won’t see them on our buses — not even has them. But you will see them on trucks getting goods to their destinations. And if you take a closer look at the trucks pulling trailers you might see another handy tool to aid truckers: the wheel rotation indicator.

Driving a large commercial vehicle is an experience like no other. Not only are you commanding something with a load of girth and longer than some high school relationships, but there are at least tens of thousands of pounds of weight at play. When you’re driving such a heavy vehicle you may not notice things like a car bumping into you or a wheel locking up. And don’t forget you have those huge blind spots too.

Truck and bus wheels can lock up for a number of reasons. One reason can be a failure in the vehicle’s braking system. The service brakes in many trucks and buses are activated with the application of air pressure. Here’s a generic diagram by supplier of brake components, Bendix:

But when you park these vehicles, the release of air pressure activates mechanical spring-operated brakes. When you hop back in and build air pressure back up, the spring brakes release. These spring brakes are also a backup system in case of an air brake failure on the road.

Sometimes, truckers may find that the spring brakes on a wheel may be frozen and not releasing, leading to the wheel dragging. You can get stuck wheels from worn out braking components, rust, bad valves or a number of different possibilities.

One way to check wheel rotation is to paint a mark on a wheel, then drive the truck, turning enough so that you can see the mark in your mirrors. Another way would be to have a spotter check to see if all wheels are moving. Or you could attach wheel rotation indicators to your wheels’ lug nuts and easily be able to check which wheels are in motion.

They work better than a strip of paint because they stick out just far enough that a trucker should be able to see them in their mirrors.

These appear to have been invented in , the owner of a truck tire shop in Canada. Broten markets his invention under the name. And unlike yesterday’s loose wheel nut indicators, there isn’t a variety of designs of them out there. There are only of the same device.

But that’s fine because they do a simple job. Is the bright yellow or orange tag spinning? If no, then your wheel is stuck.

So there you have it. The next time you’re stuck in traffic, you now know what’s going on with the wheels of the trucks and buses around you. I don’t know what you will do with this information, but maybe it’ll make your commute better. Probably not.

Hat tip to sklooner!