Darlington Race Week Breakdown

Here’s a comparison of the data from both Darlington races this week. They weren’t typical Darlington races, but I doubt anyone expected them to be.

  • We were desperate for racing. We were thankful NASCAR delivered and overlooked many of the things we normally complain about in races.
  • The drivers were coming off a long layoff period and got right on track for the first race. That’s a brand new situation, so there’s nothing to compare it to.
  • The second race was delayed and ultimately ran under the threat rain. This always leads to unusual strategy calls that may put a slower car in the lead at the end.
  • Teams had just gotten back into their shops after being prohibited from work for weeks.

The Data

In the following two boxplots, I’ve indicated data from Wednesday’s race in green and Sunday’s in red.

Who Finished the Race?

A box plot showing the percentage of cars finishing on the lead lap and the percentage finishing all laps of the race
  • The percentage of cars finishing on the lead lap was much higher than usual in both races: 60% vs about 42%
  • 92% of the cars finished the race Sunday, compared with a median of 84%.

Passing and Leading

A box plot showing passing, number of leaders and margins of victory for Darlington 2000-2020
Note: I normalized distinct leaders to the length of Wednesday’s race to eliminate differences that might only be due to race length.

This graph shows some differences.

  • There were many fewer than average drivers who led the race on Sunday and many more than average on Wednesday. The Wednesday number is so high (13) as to be an outlier
  • Green-flap passes per lap were lower than expected, moreso on Sunday than Wednesday
  • The race on Wednesday ended under caution. The race Sunday was won by a larger margin of victory than average.

Cautions and Lead Changes

The graph below shows the percentage of the race run under caution.

A column chart of the percentage of the races run under caution at Darlington
  • Both Darlington races had an above-average amount of cautions, but Wednesday more so than Sunday.

So if we break lead changes down to show changes that happen under green, after a restart, or because of a caution, we get this graph:

A column chart showing where the lead changes happened: under green flag, on restart or because of cautions
NOTE: This is done per 100 miles to account for differences in race length
  • The total lead changes were greater Wednesday, but so were the cautions. There were 11 cautions Wednesday and 10 Sunday, but Wednesday’s race was only 75% of the length.
  • There were many more green-flag lead changes on Wednesday than on Sunday. Sunday actually had only one bona fide green-flag lead change.

Accidents and Spins

This graph is also normalized to the length of Wednesday’s race.

The numbers of accidents and spins at Darlington 2000-2020

There were 7 accidents and 2 spins Wednesday, which is the second-highest number of accidents per mile in all Darlington races since 2000. But that may have more to do with anxiety over the weather than not having had practice.


Although I need to look some more at this data, it’s clear that we saw two very different races at Darlington, even though they were only separated by a few days. There was very different weather and probably some ‘back-in-the-saddle-itis’.

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