Endurance craft
Traffic
The permanent presence of slower and faster classes on the same track, and the craft of passing through it.
Traffic is the defining texture of multi-class endurance racing: at any moment a Hypercar is approaching slower GT machinery at enormous closing speeds while itself being caught by nothing, and a GT driver is being passed dozens of times an hour while fighting rivals in their own class.
Handling it is a skill in its own right. For the faster car the question is where to pass without scrubbing lap time or taking risk; for the slower one, how to stay predictable while losing minimum time. Lap-time variance in race data is substantially traffic, which is why single fastest laps flatter and stint averages tell the truth.
Part of the WEC Engine glossary. Questions with longer answers live in Answers.