Complex sentence: In that event, the track lights were extinguished, and the entrants had to compete with only the headlights on their cars; to be declared the winner, the entrant had to eliminate all other cars, while still having operable headlights.
Split into simpler sentences: In that event, the track lights were extinguished, and the entrants had to compete with only the headlights on the cars. To be declared the winner, the entrant had to eliminate all other cars, while still having operable headlights.