Every driver has been there: you're motoring along, then all of a sudden cars on the other side of the road start flashing their lights at you.
After a moment's confusion, you realise what they're flashing about. You slow down, spot the speed camera van at the side of the road and breathe a sigh of relief. Without the warnings you could have strayed slightly over the limit and faced a hefty fine and points on your licence.
The argument as to whether that's right or wrong will rumble on, but now a new poll by the Institute of Advanced Motorists (IAM) has revealed that despite the chance of prosecution nearly half of all drivers would flash their lights to warn of traps.
The survey was carried out following driver Michael Thompson's prosecution at Grimsby magistrates court last month for flashing oncoming motorists to warn them of a police speed camera. He was handed a £440 court bill for 'obstructing police'.
Nearly 70 per cent of the 4,800 motorists surveyed by the IAM believed Thompson shouldn't have been prosecuted - while 21 per cent said he should.
"The biggest reason for not flashing to warn of a speed check is safety, with "drivers who speed deserve to be caught and fined" and "the meaning of the flash could be misinterpreted" each polling a third of the votes from those who don't flash," explained IAM chief examiner Peter Rodger.
"However, safety was also used as a major justification for those who do flash to warn of speed checks, with nearly 20 per cent saying they "wanted to avoid a possible collision when drivers see the speed check late and brake harshly in response". The driver who was prosecuted for using his lights justified his behaviour by stating he used his lights to warn of a hazard."
In light of the IAM poll and Thompson's prosecution, Autoblog wants to canvas your opinion on the debate – do you think flashing your headlights to warn other drivers of a trap is the right thing to do? Or do drivers that speed deserve to get caught? We'd love to hear your opinion. Vote in our poll and then post your comments below.