Three cars hit the line which was stretched across the A908 Fishcross to Tillicoultry road close to Marchglen in Clackmannanshire.
Central Scotland Police are keen to trace three youths who were seen in the area at the time of the incident at around 10.30pm on Sunday.
The force appealed for information.
Inspector Malcolm McEwan said: “This could have had tragic consequences had a motorcyclist struck the rope, which was not easily visible.
“This is highly irresponsible and we appeal for anyone with information to come forward.”
The rope broke after the cars struck it.