Repeat 30 second runs, starting every two or more minutes.
The start is at the curved line at the track start / finish and runners cut to the inside as in a 10k race when there is room to do so safely.
After each run fit distance runners have 90 seconds (or even 60) to return to the start. Sprinters will do less but run faster and will need a longer recovery. (Up to 4½ mins.) So may novice runners.
Before starting the session, each athlete needs to decide how many reps to attempt. (Marathon runners might choose 20, 800m runners 8, sprinters 5) Then the athletes should try to run each rep at the fastest controlled fast pace that they can keep up for the whole session.
If successful the athlete will get to precisely the same point each rep.