The Purpose of Pit Road Speed Limits

NASCAR implemented pit road speeding rules in 1991. The year before, Mike Rich, a tire changer for Bill Elliott, had been pinned between Elliott’s car and the car of Ricky Rudd when Rudd came into the pits fast and locked his brakes. Rich died in surgery.

To keep things safe for the crew and officials on Pit Road, NASCAR mandates speed limits for cars on pit road. The speed limit depends on the track, with big tracks having 55 mph speed limits and smaller tracks like Martinsville having 35 mph limits.

Enforcement (or Why It’s Called “Loop Data”)

I’ve detailed how pit road speeds are measured (and also here. Oh, and here). But just to summarize it… The NASCAR timing and scoring system relies on a process called electromagnetic induction. Back in 1830, Michael Faraday observed an unusual physical process: If you move a magnet through one or more  loops of wire, it produces a current. No battery, no source of electricity: Just a moving magnetic field. (Note that the converse works. You can move a loop of wire by a magnet and you also get a current.

The physicist James Clerk Maxwell formalized this mathematically (and called it Faraday’s law of Induction). This became one of the four horsemen of the electromagnetic apocalypse that are known as the Maxwell equations, and that evolved eventually into field theory.

In order to have an electrical current, you must have a continuous path for that current to travel in — a.k.a. a “loop”. The NASCAR scoring loops are literally loops of wire set about an inch below the racing surface.

Each car has a transponder that generates a unique code when it passes over the loop, so the computer knows which car is Kasey Kahne and which is Jimmie Johnson’s. Every transponder is mounted in the exact same position in the car, so you’re always comparing apples to apples.

So that’s why we talk about ‘scoring loops’. The wires in the track have to be loops or the whole thing doesn’t work. You can see in the picture at left where the cuts were made at Charlotte Motor Speedway.

That’s why we call them “scoring loops” and that’s why the data from those loops is called “loop data”/

Getting Loopy On Pit Road

NASCAR used to score cars by having people sitting up high at the track watch and mark on a sheet of paper. One person per car and every team had their own person doing the same thing just to make sure NASCAR got it right. You can imagine when there was a big crash, it took quite some time to sort out who was where when.

The advent of automated scoring systems put all those people out of work. A computer can track all the cars at once and give the officials one thing to look at. These systems are so ubiquitous nowadays that most small racetracks have them. It’s less than $10,000 to install a complete system. Car owners buy or rent transponders and all they have to worry about is making sure that they get the right brand for the track they’re running at.  Even RC racing cars use transponders now.

The original purpose of scoring loops was just to know where the cars were on the track and when they were there. If you passed the start-finish line or loop 6 before I did so we know who goes ahead of whom on the restart.

But it turns out that scoring loops are also an easy way to monitor pit road speed because NASCAR knows physics.

Once you know how far apart the scoring loops are and you have the time it takes to go between those two loops, you know the average speed. So now you’ve not only got a scoring system, you’ve got a speed trap.

You’ll notice you don’t have to actually calculate speed. What we’re really interested in is the time it takes to go between the two points. The less manipulation you do with data, the better.

For example, let’s say you drive sixty miles down I-80 from Lincoln to the outskirts of Omaha and it takes you sixty minutes. Your average speed was sixty miles an hour. So as long as a distance in known, you don’t actually have to do any calculations – you just check the time. If you make the same distance in forty-five minutes, I know you were going faster than 60 mph.

The Increasing Importance of the Weekly Pit Map

Sometimes you can tell where the scoring loops are just by looking because you can see them in the track. But there’s no requirement that the loops be visible.

Just to make sure everyone has the same information, NASCAR has taken to handing out detailed Pit Maps that tell the teams exactly where the scoring loops are located on Pit Road. Here’s one Ralph Shaheen tweeted out for Pocono in June 2012.

NASCAR lays out in great detail where there timing lines are — literally down to the inch.

One of the things you have to realize is that these maps are not drawn to scale. And since I’m the type of person who needs to see the map to scale to really understand it, I redrew it to scale. The yellow lines above are pit in and pit out. Then there are 9 timing lines (P2 through P11) that form segments of approximately 206 feet each.

If you count pit in and pit out (P1 and P12 on the drawing), there are 10 segments. Note that you have to have the start-finish loop on pit road so cars get credit for the lap if they complete it while on pit road. But NASCAR doesn’t use the Start/Finish scoring loop for pit road speed monitoring.

Pit road speed limit at Pocono is 55 mph, but they give you 5 mph, so it’s really 60 mph.

60 mph is 88 feet per second, so it should take a car going at exactly the maximum speed 2.347 seconds to go 206 feet 7 inches. (An extra inch adds about a thousandth of a second to the time.)

 The 2012 Pocono race was one of the first races where the scoring loops came to the attention of most race fans. As you’ll note from Shaheen’s tweet, there were some difficulties keeping the cars at pit road speed.

There were a huge number of pit road speeding penalties at that race, which was likely because there didn’t used to be ten scoring segments. Most tracks up to that point used to have three or four segments — maybe five at the biggest tracks.

Now, if you’re not speeding, it shouldn’t matter how many times you’re measured, right?

There were 22 pit road speeding penalties.

Twenty of those 22 came in the very last segment. Now, we know the drivers are anxious to get out there and stake their place for the restart. But you’ll also notice that the last segment is the shortest.

The shorter the segment, the less leeway you have and the more likely you are to get caught if you do happen to go a little over.

 

If teams were content to try to go as close as possible to the speed limit, we wouldn’t have a problem. But you’ll see cars do little maneuvers like suddenly blipping the throttle right before skidding into their pit box.

The Problem with Average

Remember the example of driving sixty miles in sixty minutes? Well, that means your average speed was 60 mph. You could’ve been going 80 mph for part of the way and 50 mph for the rest of it.

Averages, by their very nature, smear out the details. The longer you average, the more smearing and the less details you get. Look at the plot below, which shows a bunch of different speeds over 10 seconds. The red one is just going 60 mph the whole time. The teal one is going 100 mph half the time and 20 mph the rest. THEY ALL GIVE YOU A 60 mph AVERAGE.

Your average car on pit road doesn’t go the speed limit if they can avoid it. They play all the games they can to get in front of someone else or hit that start-finish line before someone else.

The Preferred Pit Boxes

When NASCAR had three or four segments for a long pit road like Pocono, the teams had a lot of leeway. Let’s say in the map above, that you get pit box 30. That’s the one right after the first opening.

You cross the scoring loop labeled P4 — but look: the next loop (P6) is actually at the far end of your box. You know where the transponder on your car is, so you know that when you stop in your box, you will not have passed the next scoring loop.

 

Remember that you normally have to spend 2.35 seconds in that segment. But you’re going to spend 12 or 13 seconds in your pit box. When you average in a bunch of zeros, it reduces your average speed by A LOT. If you have a 13.5 second pit stop and are at right at 60 mph entering the box, the total time between your triggering those two scoring loops will be 15.85 seconds. Your average speed:

That gives you a heck of a lot of leeway to go faster than 60 mph as soon as you’re past that first scoring line.

You could spend the 2.35 seconds getting to your pit box going 200 mph and still not break the speed limit because they only measure averages. Of course, it’s not possible in 200 feet to speed up from 60 mph to 200 mph and then stop. But if it were, you could do it and still be well within the rules.

But that’s why you see drivers doing those goofy speed up/slow down maneuvers on pit road. They know exactly where they can speed and they are trying with everything they have to exploit those areas.

NASCAR Cracks Down

That’s why we have all these goofy speed up/slow down maneuvers and the rationale for why teams pick their pit boxes. Under the map above, there are few select pit boxes that give you a real advantage because you can play those games where someone in a different box can’t.

As usual, NASCAR watches how things evolve. At some point, they put their foot down.

In Kentucky, Martin Truex, Jr. blipped the throttle trying to get a few fractions of a second advantage by speeding up as he approached his pit box. But that blip caused him to pass the leader (Harvick). Since he was on the left of Harvick, he got penalized because you don’t pass on the left on pit road. (Another safety rule).

So when teams got to New Hampshire, they found that NASCAR had added timing loops. Indianapolis went from six timing segments on pit road to twelve. And here’s the pit map for Pocono for the August race.

There’s just a few more scoring lines that before, huh? It also makes for one heck of a cluttered-up map. So let’s redraw it and compare it to what the lines looked like before (including for the June race this year).

There are now 18 segments on Pit Road, averaging about 100 feet in length with the exception of the first segment. The first three boxes are greyed out because they are no longer used since ‘full field’ was scaled back to 40 cars.

If you look at the pattern of adding loops, NASCAR has a pattern: They are putting a scoring loop every 3-4 pit boxes.

Look back at the example I gave you about pulling into pit box 31, which I’ve highlighted in yellow in the diagram above. There’s now a new scoring loop (P8), right in the middle of the gap. You can still speed up from the P8 loop to your box (highlighted in yellow); however, you can’t speed as much because you’ve got a shorter distance to slow down in.

They’ve tried to keep the segments all approximately the same size to equalize the boxes so no one gets an unfair advantage.

Are Shorter Segments the Answer?

I guess it depends what you think the question is. Will shorter segments make it harder for drivers to speed on pit road? Yes.

Will shorter segments make pit road safer?

That answer is not so clear.

The shorter the segments on pit road, the more attention drivers have to pay to their dash. They can’t make up for accidental speeding by compensating and going well under the speed limit. They simply don’t have the time.

This means drivers are spending more time looking at their dashboards as the traverse pit road.

When their eyes are on their dash, they’re not looking up. They may catch the crew member reaching for a stray tire or stretching out an air hose out of their peripheral vision.

In an interview reported by Dustin Long, Aric Almirola pointed out that drivers aren’t looking up from their dash until they hear their spotter or crew chief say five or ten pit stalls away. Even then, they’ve got one eye on the dash to make sure they aren’t speeding. If I’m the front tire carrier or changer and I’m jumping out in front of the car as it pulls into the pit box area, I’d sort of like the driver to be looking up a little more than that.

What I’d argue is that reducing speeding beyond what we’ve got now isn’t necessarily making pit road any safer.

How About Even More Precise Measurements?

When you get nabbed speeding on the expressway, there are no scoring loops. A radar gun sends out an electromagnetic wave that bounces off your car. The wave changes as a result of its interaction with your car via the Doppler effect, just like that weather radars. The returning wave is measured and your speed at the moment the wave hit your car is revealed.

This type of measurement is called instantaneous because it gives you a snapshot of your speed at that particular instant. (As opposed to average, which gives you a much broader picture.) Instantaneous measurements would eliminate entirely the ability of drivers to play games with their speed because they would be penalized if their speed rose about the limit at any point.

The problem with instantaneous measurements is that now the driver is going to be entirely focused on his or her speed on pit road and this would almost necessitate a speed limiter.

Radar guns wouldn’t be a feasible way of monitoring speed on pit road. They work great for baseball where there’s one ball at a time. Radar guns have to have a clear path to the car and you have to be positive which car the wave you’re measuring bounced off. Given the sheer number of cars on pit road and the weaving as they go in and out of their boxes (and avoid running into each other), radar guns are probably not going to work.

GPS can provide instantaneous measurements and doesn’t depend on having a clear line of sight; however, monitoring pit road speed with GPS is frankly overkill unless you decide you want that to one more challenge for the drivers. Personally, I’d rather see the race be in the pitbox and on the track. If you’re going to be that precise, all you’re going to do is increase the number of penalties. Teams will set their tachs to stay three tenths of a mph under the limit just for safety and every now and then, someone will lose a race because their tach was off by a half of a percent.

The Solution?

Let’s not even consider getting rid of pit road speed limits because that’s just plain ignorant.

And asking the drivers not to play throttle blip games to get every last possible millisecond won’t be effective either.

The solution is likely using pit lane speed limiters like they do in other series like F1. The driver hits a button as they come on to pit road and that activates an engine rev limiter. Implementing this would be much easier given NASCAR’s recent move into EFI than it would have been many years ago.

There are issues with pit road speed limiters. Everyone is always worried about teams using pit road speed limiters to help with traction control. Most pit road speed limiters only work in 1st, 2nd and 3rd gear so they can’t even be activated in 4th.

Once a pit road speed limiter is engaged, the driver would be able to focus his or her attention entirely on what’s in front of them: other cars, crew members and officials.

I understand and appreciate the argument that giving the drivers some leeway is all part of the game. Taking things out of their hands is less fun. I agree entirely. I like the idea of letting drivers take their chances with the rules and see what they can get away with. But I draw the line on that argument the moment we get into it impacting the safety of the people on Pit Road.