PIt Road Speeding FAQ

 Pocono, Timing and Scoring  14 Responses »
Jun 102012
 

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.

Is More Data Always Better?

 Richmond, Timing and Scoring  1 Response »
Apr 292012
 

Saturday’s race in Richmond was a festival of miscues.  Carl Edwards mistakenly thought he was leading, then he jumped the restart, although he wasn’t the one to lead the restart because he wasn’t the leader.  One would think we have the data that could prevent incidents like this.  We probably do.  But do we want to use it?

NASCAR Timing and Scoring

A transponder is a device that translates one type of signal into another.  For example, the track position of the cars is measured using induction from loops of wire embedded in the track and translated into an electrical signal that is passed along to timing and scoring.

Like computers, timing and scoring systems merely report exactly what they are asked to report.  The official timing and scoring system works on the basis of ‘scoring loops’ – which are literally loops of wire embedded in the track.  The number of loops in the track depends on the track.  There are more loops at longer tracks and fewer at shorter.  The loops are in the main part of the track and embedded in Pit Road (which is how they catch speeders). The two faint lines running along the track at right (from top to bottom of the photo) are a scoring loop in Pit Road at Charlotte Motor Speedway.

When a caution flag appears, everything goes back to the situation at the last scoring loop passed.  Even if car A passes car B, if it happened in-between scoring loops and a caution comes out, car B is still the leader.  Television replay is used in the last laps of the race.  Timing and scoring has a discrete number of measurements around the track.

There are, of course, more measurements available.  Television shows you much more frequently updated data from a different system.  How many times have you watched the tracker on television (or Pit Command) and seen the lead switch back and forth during caution as the drivers sped up and slowed down while scrubbing tires?

If Car A passes Car B, that information is updated immediately on the television system.  The official scoring loop system is updated only after a scoring loop is passed.  This is why there was so much confusion Saturday night.  With a penalty on the 48 team, the 99 team thought they were the leader – as reflected by the scoring pylon and, it seems, the officials on the spotter’s stand.  See Bob Pockrass’s story for a detailed explanation.

We Have the Technology: Why Don’t We Use It?

I received a lot of comments to the effect of “NASCAR has more detailed data – we know that because we see it on television and RaceView/Pit Command.  Why don’t they use it?” Two comments.

1.  The official timing and scoring is based on the track scoring loops.  Television replays are used at the end of the race, but the rest of the data you see on television is informational.  It is not the data of record.

2.  I interviewed some people from SportVision (the company that provides the television with the information you see) earlier this year in the context of whether it was possible for teams to intercept data.  Their tech people repeatedly made the point that they acquire such a huge amount of data that analyzing it in real time in any reliable detail is not feasible at present.  They transmit a subset of that data directly to the television, but I was under the impression that the data you’re getting from Race View may not give you results  accurate enough to base race calls on during a race.

This raises a much larger question:  Do you want a sport where technology contradicts what the audience thinks they saw?  It sure looked at thought Carl Edwards obviously accelerated way before the starting box – but we know that human perception is not objective and not always accurate.  Your perception was affected to a large extent by the fact that Stewart spun his tires and didn’t accelerate.

NASCAR is data intensive like few other sports.  NFL fans don’t need to know how fast two players were going when they collide – they just need to see that player B stopped player A.  Being a data geek, I want to get my hands on all the data I can; however, given the numerical literacy level of the country (A huge number of people can’t understand even basic charts and graphs), basing a sport more and more on technology is dangerous.  Technology can enhance your enjoyment of a game – like seeing the speed at which a fastball hurtles across home plate – but I don’t think most people want to have to follow the numbers that closely just to understand what is going on.