Dr. Diandra: What loop data can — and can’t — tell us about passing

Drivers expressed some strong opinions about the Next Gen car’s passing ability after Bristol. Kevin Harvick and Denny Hamlin, among others, felt the car made it too hard to pass.

Brad Keselowski agreed that it was hard to pass, but opined that it’s supposed to be hard.

The passing complaints surprised me. NASCAR’s loop data reported 2,690 green-flag passes for the 2022 fall Bristol race. That’s 980 passes more than the 1,710 green-flag passes recorded for last year’s fall Bristol race.

So are the drivers wrong? Perhaps their comments reflect the accumulated frustration of a long night plagued by so many equipment problems?

Numbers don’t lie. But they also don’t give up their truths easily.

Each car carries a transponder that emits a signal unique to that car. Wire loops embedded in the track (and on pit road) record each of these signals. The loops capture a car’s precise position on track — and its position relative to other cars.

The graph below shows green-flag passes by race for the 2022 season. Because races are different lengths (and tracks different sizes), it’s hard to compare data.

But superspeedway races stand out for having thousands more green-flag passes than other types of races.

I’ve always been skeptical of passing metrics at superspeedways. Those extraordinarily large numbers just tell us that two or three lanes of cars traded positions a lot. That doesn’t measure passing in a way that illuminates the racing.

What I hadn’t appreciated until I dove into these numbers is that they’re not exactly what you think they are at other types of tracks, either.

According to loop data, Chase Elliott made more green-flag passes than any other driver at Bristol. But did it really take him 154 passes to go from 23rd