PIt Road Speeding FAQ

A new record for pit road speeding penalties was set at Pocono this weekend.  Drivers were able to compensate and there weren’t a lot of penalties after the first set.  The question remains:  why all the speeding penalties?

The Facts

Here's the list of pit road speeding (and other) penalti... on Twitpic

There were 10 scoring segments on Pit Road and almost all of the speeding penalties were in the last segment (Pit Road exit).  The photo at left was tweeted by @nateryan after the first round of penalities.  You can view a larger version here.  (Thanks, Nate!)

A few of the drivers shared how much they were told they were over.  Harvick said it was 0.06 mph.  That’s not much.

A Pit Road map showing all the timing and scoring lines was available well before the race.  Ralph Shaheen tweeted the map during the race (Thanks, Ralph!).  NASCAR doesn’t draw their maps to scale (which drives me nuts), so I re-drew the map to scale.  I just realized that I labeled P2 twice.  The first one on the left is P1.  This makes for 10 loops (the start/finish is not part of the pit road timing system).  Note that each of the loops is roughly 207 feet – except the last one, which is only roughly 80 feet.

Questions and Answers

Q. How do they check pit road speeds?
A. Scoring loops embedded in the pit road concrete send an electrical signal when the transponder in the car passes via a process called electromagnetic induction. It’s the same process used to keep track of where the cars are during the race. The transponders are mounted inside the car (I believe they are just a little forward of the drivers’ seat, inside the door.)

The important thing is that they are measuring average speed over the timing segment, not instantaneous speed.  Instantaneous speed is (just as it sounds) your speed at a particular instant.  A radar gun measures instantaneous speed.  If you are on the expressway, you can get a ticket if you go over 65 mph at any instant.  In NASCAR, your average speed is the important thing.  Pit Road speed at Pocono is 55 60 mph.  You can go 50 mph for half the time and 70 mph for half the time and your average speed would be 55 mph.

Q.  Wait – why isn’t pit road speed 55 mph?
A.  Teams get 5 mph over the “official” Pit Road speed.  They all are trying for 60 mph, so let’s not pretend anyone is thinking about going 55 mph.  The Pit Road speed limit is effectively 60 mph.

Q. Do teams know where the loops are?
A. They ought to. It’s not a secret – NASCAR puts out a map showing all the timing lines. Pocono changed the number and location of the timing lines when they repaved Pit Road. It’s hard to believe that a competent crew chief wouldn’t have asked for this information. Given that there was a significant change, it’s also hard to believe that a competent crew chief didn’t discuss this with his driver.  Knauss and a number of other crew chiefs walk Pit Road and inspect all the pit boxes to check on things like cracks, unevenness and little things that might throw off the pit crew.  If they are that attentive to the tiny details, they’d have to have had a major brain lapse not to have asked about the timing lines.

Q. Why doesn’t NASCAR move the scoring lines to keep things interesting?
A. They are embedded in the track. The picture at right shows the loops in Pit Road at Charlotte.  You can’t just pick them up and move them like a garden hose.  If I were repaving a Pit Road, I would play it safe and put in a whole bunch of them, because you can select which ones you want to use for timing and scoring.

Q.  Why didn’t they stop the race and re-calibrate their radar gun after all those penalties?

A1.  Aaragh!  There is no radar gun.  I know people thought it was funny to say because “why don’t they recalibrate their scoring loops” isn’t very humorous.  But don’t saying there is a radar gun because it confuses the people who don’t know.

Would you really want the instantaneous speed to be monitored?  Seems to me that this would officiating a race needlessly complicated.

A2.  I am very skeptical that there was anything technically wrong with the scoring loop system.  It is tested and double tested and the changes of a malfunction are fairly low.  My intuition is that the system was working exactly how it was designed to work.

Q.  Why don’t they just give the drivers speedometers.

A.  Because tachometers are actually 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 the lighted versions they have now.  I’ll take a dial over a light any day.

Q.  It seems silly to penalize someone for going 0.1 mph over the effective pit road speed limit.

A.  It does; however, where do you stop?  If you tell them you’re giving them another 0.1 mph, then the person who gets caught going 0.16 mph over the effective limit will complain that he was only 0.6 mph over the limit.  NASCAR can’t win on this.  You have to draw a line and it’s going to be arbitrary.  Everyone races under the same conditions, so where the line is placed really doesn’t matter.

Q.  Why don’t they just show us the speeds on the television?

A.  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.

Q.  So why all the speeding penalties?

A.  We don’t know for sure, but here’s my thoughts.

1.  I’m 99.99% confident that the problem was not due to malfunctioning of the system.

2.  TNT advanced the theory that many teams didn’t know the scoring lines had been moved.  Look at the photo and who got nabbed.  The 48 got nabbed twice – once on the pit stop and once while serving the penalty for the first speeding incident.  Of all the crew chiefs who would  would have been on top of the location of the scoring lines, Chad Knaus is #1 on my list.

3.  The last segment – the one that gave so many people trouble – was only 80 feet.  If you’re going 60 mph, you spend 0.94692 seconds in that segment.

a.  At 60 mph, you spend 2.3475 seconds in the long scoring loop 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.  It would be really interesting to know the accuracy of the system.

b.  A shorter segment is less forgiving.  The drivers are not going at constant speed throughout the loop.  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 withing the boundaries of the timing and scoring system.  I’m a little skeptical about the reliance on tach lights – but I’d need to know more about how the lights are set before I could say for sure.  Drivers have many things going on and light may make their lives much easier, but a light is never as accurate as a dial.

NOTE added:  Jimmie Johnson said after the race that NASCAR draws the yellow line at the end of pit road such that the nose of the car is at the yellow line when the transponder is at the scoring loop.  He suggested that the team might want to test that out themselves just to verify the accuracy of the line relative to the transponder.  As I said above, if any team was on the location of the scoring loops, it would be the 48.   I do not believe that not knowing where the lines were was the problem.

NOTE:  Robin Pemberton said on NASCAR Victory Lane that the old segments used to be 274 ft long.


  1. Hi Bob – back in the USA?

    Are you asking about the time difference if the segment was a slightly different length?

  2. The speed limit was set for safety reasons for the pit crews, so going 70 to 75 mph then 40 to 45 at other times on the pit stop to average out to a given mph, doesn’t keep the pit crews safe when they are going faster than the speed limit.

    • Eric: That is a really good point. Playing around with trying to game the timing lines isn’t helping preserve safety on Pit Road.

  3. If the transponders are located away from the front bumper, and the driver is timing his “clear of pit road” based on the bumper crossing the line, there must be an offset between the actual scoring loop and the painted line. Could there be some error here? Especially in a very short segment, it seems like a little bit of measurement error could make a large difference.

    • Steve: Definitely an issue. I don’t about professional drivers, but I do a pretty lousy job of estimating where my bumpers are when I’m trying to park. I think the key thing here is, as you point out, the shorter the segment, the more of an issue it is. It would be helpful to find out how long the segments are at the short tracks. The have fewer segments, but I wonder if they have any that are 83 feet? Anyone know?

  4. I have a feeling that with such a short loop that such little details as just raising the tire pressure a little could have advanced the speed enough to through the tach reading off. They aim to get SO close to the 60mph that there’s very little margin for error. They setup the christmas tree lights on the tach pre-race and i don’t think they can adjust them after (easily). The driver just knows if they see red they better lift. I know that NASCAR used to overstate the accuracy of their numbers, not that long ago you could look at their “Margins” between cars and you’d see (0.06, 0.13, 0.19, 0.26) as the margins…which jumps out pretty quick to show that last figure was pretty much a barely significant figure so to speak.

    Teams will likely just have to set a higher tolerance (margin of error) when having a segment so short…the slightest issue in terms of mis-measuring the distance of those last lines could have caused the same issue…if those lines aren’t completely parallel (like i think TV has shown they aren’t on some tracks…go figure) cars running to the inside or outside of pit road may have been at a marginal disadvantage to get tagged.

  5. If you map the speeding penalties onto the pit road stalls, you will see three areas took the repeated hits. I’m betting something about the sensors under pit road being screwed up.

  6. Hi Dr, D,

    As usual, you explained the pit road speeding issue so I can understand it. I did find it strange that some of the teams didn’t pick up the map showing where the loops were. I bet that doesn’t happen again.

  7. The teams are all very well versed about the hows and whys of the speed limits. Teams often use this to their advantage a la Keselowski who at a race last year passed several cars on pit lane to take a lead by travelling more than doubling pit road speed simply because he had the last pit stall – a stall which was part-way into the last timing zone – and the 14 or so seconds spent servicing the car in that zone meant he couldn’t possibly be over the “average” speed limit no matter how fast he exited. What is overlooked here is that although NASCAR provides these sheets to any chief that asks for them, NASCAR changed the configuration at Pocono without the courtesy of a “heads up” to the teams. The previous loop-layout was in place for years and teams like the 48 had that layout nailed. It is inexcusable that NASCAR would change parameters without communicating that to the teams.

  8. According to the tweeted photo there was “only” 16 speeding penalties, the rest came from pitting too soon and not obeying NASCAR’s request. Yet the official number of speeding related penalties is 22…
    What am I missing?

    • John: Nate Ryan tweeted that photo midway during the race. That was an interim report and not the final one. Thanks for asking – I should have been clearer about that.

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