You hear it all the time in racing nowadays: a driver has been penalized in some way for exceeding track limits. But what, exactly, are track limits? How are they defined? And why are drivers penalized? This guide will walk you through everything you need to know.

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To put it very simply, track limits define the boundary between the specific area of track and runoff that a driver can drive on and the area of runoff that is not appropriate to drive on. Track limits are enforced as a way to prevent a racer from gaining an unfair advantage.

Track limits became a facet of motorsport as a result of safety. In the past, if a driver drove off the track, he would drive through grass or gravel, which resulted in a crash more often than not. Anyone who has ever driven a road car through an asphalt-to-gravel transition knows that a different road texture requires different driving skills, which isn’t exactly something you can easily mitigate when you’re racing at hundreds of miles an hour.

Many tracks now implement large paved runoff areas instead of gravel traps or grass. This prevents crashes because a driver is more easily able to correct his path and return safely to the track.

But if you pave it, racers will come. An asphalt runoff area doesn’t involve the inherent penalty that a gravel trap would; you can easily cruise through the runoff at speed. Yes, you might struggle a little driving over raised curbs, but if that extra swath of asphalt gives you an advantage, you’re going to take it.

You can see what I mean in the video below. When IndyCar came to the Circuit of the Americas, track limits were not implemented in Turn 19. That meant drivers used all that extra paved runoff area because it provided a much faster line around the track. That, in turn, changed how they approached Turn 20 and how they came off of Turn 18.

Compare that to Formula One at that same corner. With Turn 19 track limits enforced, drivers needed to take a much different line through the turn:

Let’s pretend we’re back in the 1970s. If COTA had been built then, that Turn 19 runoff probably wouldn’t have existed. It would have been gravel instead. A driver who ran wide at Turn 19 would have been naturally penalized by losing control, crashing, or having to slow down dramatically, likely accruing damage. Track designers would have intended a certain line be used around the track, and the gravel would have been the punishment.

Now that we have paved runoff, track or series officials often determine an artificial penalty be applied for the racers that exceed the defined track limits.

Track limits are essentially defined based on the intended layout of the track. At most tracks, a white line traces the exterior of curbs in corners; that white line represents the track limit. In some instances, track limits can be extended, but it’s a rare occurrence. The stewards want you racing on the specific strip of asphalt identified as the track.

The purpose is to keep cars racing on the intended track surface as much as possible. After all, the track designer designed the track. Runoff isn’t track. Stewards don’t want you racing on it and getting an advantage.

There are debates about how to dictate track limits beyond just the white line. Many people argue for the reintroduction of gravel traps, but the chances of that happening are slim. We got rid of them for safety reasons. Convincing any of The Powers That Be to regress is not happening.

Others have suggested making the current curbs taller, which generally works well to deter four-wheeled cars from running over the limit. The main problem is, you can’t use those tall curbs on tracks that host motorcycle races. Once again, it comes down to safety: if a rider clips the curb, s/he can be thrown from the bike, and because riders are more physically prone than drivers, you want to avoid that as much as possible.

Track limit enforcement is… iffy. Technology has created a lot of more objective ways to note when a driver exceeds track limits, such as cameras or sensors built into the track. If you trigger the sensor, you get a penalty. That’s fairly straightforward.

In some cases, though, race stewards have to determine if something is a penalty by rewatching footage from local cameras to see if a tire crossed the track limit boundary. This is where things get a little questionable because it’s all up to personal interpretation. Some drivers might get penalized while others get away scott free. Some drivers might get penalized for crossing a hair’s breadth over the line. Others might get away with a more blatant infraction.

That’s part of why fans have a lot of emotions about track limits. There’s a level of arbitrariness to it that can be frustrating. Any time you leave rule interpretation up to the stewards, people are going to call bias.

In a lot of ways, the whole concept of ‘track limits’ can be confusing for spectators, both at the track and at home. When you’re sitting at the track, how are you supposed to tell that a driver got a penalty for a tire being a millimeter over the white line. Even hearing the explanation at home can be confusing, since we’re often operating in tiny margins of error.

Whatever the case, you should try not to get too hung up on track limits. They’re part of an ever-growing racing rulebook, and we’re not going to see the end of them any time soon.