# How pit road speed limit is calculated

January 05, 2015, NASCAR.com

Find out the method behind the madness of NASCAR pit stops

There isn't a policeman hiding behind the pit wall with a radar gun, and there aren't speedometers in NASCAR racing vehicles. So how do teams and officials measure pit-road speed limits with a certain amount of precision?

We've all seen it happen -- a driver will seem to be minding his own business, making his way down pit road when all of a sudden he gets word that he's been penalized for speeding.

But this is NASCAR -- cars are supposed to go fast, right?

Yes, but during certain points of the race and in certain locations a particular speed needs to be maintained in order to establish safety for drivers, pit crews and fans. This comes into play on pit road because of the potential frenzy of 43 cars trying to beat each other to the line for track position.

Sure, this all makes sense, but in a NASCAR world where more than two miles separate the largest from the smallest tracks, how is this speed calculated? And is it the same for all tracks?

The pit road speed varies from track to track, with shorter ones (Bristol, Martinsville, New Hampshire) exhibiting a slower speed than the behemoths of Daytona, Talladega, Indianapolis and Michigan. NASCAR rules allow for a 5-mph buffer over the posted speed limit; it's a cushion that teams exploit on a regular basis.

At Talladega, for example, the pit-road speed limit is approximately 55 mph. At a short track such as Martinsville, that speed would be too dangerous, so the pit-road speed limit is approximately 30 mph.

Despite those differences, the general rules remain the same at each track. Each pit road is split up into zones, the number of which is determined based on how long the stretch is, making it easier to determine when a driver goes too fast. All teams are informed of the exact location of all sections and if a pit-road speeding penalty occurs, NASCAR informs the team where it happened.

As far as calculation goes, it all comes down to physics. The answer lies in scoring loops -- a series of electronic sensors below the pit road pavement, which calculate distance over time to measure car speed.

For drivers, the trick to staying within the limits is based on their tachometer readings. Teams can program their tachs before the race to know which amount of RPM (revolutions per minute) equals the legal pit road speed.