Pit Road Speeding FAQ

One of the most common penalties in a NASCAR race is speeding on pit road. In 2020, 78.7% of all driver pit-road penalties were speeding. So how does NASCAR measure and assess pit-road speeding penalties?

How Does NASCAR Know Where the Cars Are?

Back in the day, one person for each car was the official ‘scorer’. He (or often she) marked the car’s position every lap. Nowadays, however, the process is entirely automatic.

Scoring loops are embedded in every NASCAR track. You can identify them pretty easily. It’s not like NASCAR is trying to hide them.

There are two lines because these are literally loops of wire in the track. Loops, because that’s a requirement for electromagnetic induction.

Back in 1830, Michael Faraday observed that a magnet moving through a loop of wire produces a current in the wire. That’s with no battery or other source of electricity.

Each car carries a transponder, located just a little forward of the driver’s seat, inside the door. Each time a transponder goes over one of these scoring loops, it sends an electrical signal. Every transponder is unique, which allows the people in timing and scoring to tell which car is which.

Even on Pit Road?

Yup. Here’s the scoring-loop diagram for Pocono back in 2012. I mention that it’s 2012 because NASCAR added scoring loops to Pocono in 2016. Apparently, a number of teams didn’t catch the change. That resulted in a race with an enormous number of pit-road speeding penalties.

What Do They Measure?

The scoring loops blip when a car passes by. So they are measuring the time it takes for a car to travel between two scoring loop. They know the distance between the two loops, so you use:

speed=\frac{distance}{time}

to get the speed.

But note that this measures average speed over the timing segment, not instantaneous speed. 

Instantaneous speed is (just as it sounds) your speed at a particular instant. Radar guns measure instantaneous speed. On the expressway, you can get a ticket if you go over 65 mph at any instant. 

In NASCAR, average speed is the important thing.  Pit Road speed at Pocono is 60 mph.  You can go 50 mph for half the time and 70 mph for half the time and your average speed would be 60 mph.

In fact, the graph at left shows five speed vs. time traces. Each has the same average speed, but the instantaneous speeds vary all over the place.

That’s why you see drivers playing all those games with speeding up and slowing down. They don’t have to be at or below pit road speed at every moment in a given segment. Only the average speed matters.

So That’s Why They Pick Pit Boxes with Timing Lines in Them?

Again, Yep.

If you spend twelve seconds inside your pit box, you can speed out of it without any worry that you’re going to have an average speed higher than the limit. That’s one reason that NASCAR added timing lines on many pit roads: some pit boxes had significant advantages because of where they were located.

Are Timing Line Locations Secret?

A Pit Road map showing timing lines is available to the teams and the media. Before that was common, crew chiefs walked the track to find them. No effort is made to hide their locations. Ralph Shaheen tweeted the Pocono map during the race to help explain what was going on.

Note that NASCAR doesn’t draw their maps to scale.

What’s with This 5 mph ‘Tolerance’?

Back in the day, they used varying measurement instruments with varying accuracies. The 5 mph tolerance is a relic from that period. If Pit Road speed is 55 mph, it’s actually 60 mph. But if you’re 60.01 mph, you will get a penalty.

How Often Does NASCAR Move Timing Lines?

Given that they are embedded in the track, moving timing lines is a major undertaking. It’s not like moving a garden hose. 

If I were repaving a Pit Road, I would play it safe and put in a whole bunch of them. Then you have some leeway for the future.

Are Some Tracks More Conducive to Pit Road Speeding?

There are two reasons. The first is that track position is more important at some tracks than others. Drivers might be willing to chance a penalty if they can make up a good number of positions.

The other reason is when tracks are small enough that pit road has to extend into the turns. Let’s look at the penalties for the Spring 2021 Phoenix race.

Remember that they’re measuring time and inferring speed. When you’re on a curve, though the distance you travel isn’t constant.

It’s the old marching-band problem. When a band has to turn, the people on the outside of the turn have to walk much faster than usual. The people on the inside of the turn almost march in place. That’s the only way to keep the line straight.

The same thing happens here. Let’s say two drivers travel at the same speed, but one is on the outside of the turn and the other is on this inside. The outside driver takes longer than the inside driver. So, given how NASCAR measures, it’s possible for one of them to ‘speeding’ and the other not — even though they were going the same speed.

That’s something the driver has to figure out. Not having practice doesn’t help new drivers figure it out.

Can’t They Just Give the Drivers Speedometers?

Because tachometers are more accurate than speedometers.  You can tell your speed to a fraction of a mph with a good tach.

The divisions on a tach are usually 100 rpm. If the driver can read the gauge to 100 rpm, for a typical gear ratio (i.e. let’s say a 1.45:1 second gear and a 4.22 rear end gear), each 100 rpm step on the tach corresponds (for 82.1 inch circumference tires) to 1.37 mph. If you assume that the driver can read the tach to 50 rpm, that’s 0.64 mph.

Besides – when drivers get caught speeding, it is usually because they were trying to cut it too close to the limit, not because they didn’t know how fast they were going.  Remember that you are being judged on average velocity and both the tach and a speedometer measure instantaneous velocity.

I’m not a fan of relying too much on a row of lights that goes red if you’re over or close to over. I’ll take a dial over a light any day (as long as it’s a BIG dial). Drivers have many things going on and light may make their lives much easier, but a light is never as accurate as a dial.

Why Penalize Someone for Going 0.01 mph over the Effective Pit Road Speed Limit?

A.  Where do you stop?  If you tell them you’re giving them another 0.1 mph, then the person who gets caught going 0.11 mph over the effective limit will complain that he was only 0.01 mph over the limit. You have to draw a line. Everyone races under the same conditions, so where the line is placed really doesn’t matter.

Why Don’t They Show Pit Road Speeds?

I addressed this before in more detail – just my opinion, of course.  The more data NASCAR hands out, the more they’ve got fans picking apart every aspect of the sport.  I watch races with timing and scoring on my computer, twitter, the radio going over the TV, etc.  I like love data.  At some point, though, you want people watching the race and cheering on their favorites, not picking every millisecond of data apart. It’s a good race for me when I don’t want to look away from the television.

Are Some Segments More Likely to Catch Drivers?

Short segments seem to be trickier. For an 80-foot segment going 60 mph, you only spend 0.947 seconds in that segment.

At 60 mph, you spend 2.3475 seconds in a 210-foot segment.  Let’s say you’re going 60.06 mph.  In the short segment, you would spend about one millisecond (one thousandth of a second) less in the segment.  In the long segment, you save 2.3 milliseconds in time. 

Shorter segments are also less forgiving.  If you push too hard on the throttle for an instant, consider how that affects the average speed if that instant is out of 2.3 seconds or 1 second.  The drivers are constantly trying to figure out how to get maximum speed within the boundaries of the timing and scoring system. 

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