Like HowStuffWorks on Facebook!

What was NASCAR's gentleman's agreement?

NASCAR Transponders


During the 2003 racing season, NASCAR put in place a new rule: each driver's position would be "frozen" as soon as a caution was thrown. The exact position was determined by transponders in the cars and receiving loops positioned around the track. We'll explain the transponder system in more detail in a moment. This rule solved the "racing back to the line" problem -- no one had any incentive to race to the caution, since they couldn't gain any positions. What had been an unwritten rule was now official.

There was a problem with freezing the field, however. It became almost impossible for a driver to regain a lost lap. Having more cars on the lead lap makes for more interesting races and is often used as a gauge of parity within a racing series, so it was in NASCAR's best interest to give drivers a chance to get their laps back. Therefore, they instituted what many people refer to as the "Lucky Dog" rule. It is also known as the Free Pass, but the NASCAR rulebook terms it the Beneficiary Rule. This rule allows the lapped car with the highest track position to regain a lap whenever a caution is thrown. That is, if three cars are all one lap down, during a caution the car that is ahead of the other two on the track will get the lap back.

There are no limits on how many times a car can use the Beneficiary Rule in a single race, or how many laps down a car can be and still use it. Several drivers have won races after using the rule, and in one strange case, Kyle Busch used it five consecutive times to come back from being five laps down. He lost the laps due to mechanical troubles at a road course. Because road courses are longer and slower tracks, lapped cars are rarer, and there weren't any at the time (other than Busch). A series of caution flags allowed Busch to get all the lost laps back. There are many critics of this rule, but so far, it remains in place.

The transponder system is the key to determining every car's position on the track at the exact moment a caution is thrown. Each car carries a radio transponder that gives off a short range radio transmission of a seven-digit code number. By NASCAR rules, the transponders are mounted on the fuel cell. At varying points around a track, wire loops are embedded about a foot (0.3 meters) below the track surface. These loops receive the transmission from the transponder. NASCAR can also deploy free-standing transponders around a track if they want higher resolution. The loop immediately sends this information, via a wireless network -- with redundant fiber optic connections, just in case -- to a computer system that logs each car as it passes each loop and at what specific time. This system can be used to track where cars are in relation to each other on the track and it can also record lap speeds. The information is even sent to laptop computers used by the pit crews, so they can see scoring and timing data in real time.

Trying to figure out where everyone was on the track using human spotters would be incredibly difficult, and using video replay would be time-consuming and confusing. While the new rules may not be a perfect fix in the absence of the gentleman's agreement, transponder technology definitely makes things a lot easier.

For more information about NASCAR and other NASCAR-related topics, follow the links on the next page.