They say on-board cameras fitted to drivers' vehicles may have recorded a silver car similar to an Astra parked by the side of the road which was connected to the crime.
Officers are asking to all motorists, motorcyclists and cyclists who were travelling in Blackburn's Main Street at around 9.15pm on Friday, June 20 to contact them.
The attempted robbery at the Murco garage was carried out by a man described as white and of medium build.
He was wearing:
- Dark blue or black shiny shell or waterproof style hooded top
- Dark blue tracksuit trousers with single white piping down the outside of each leg
- White logo on upper left thigh of trouser leg
- White trainers
- Llight blue surgical disposable gloves
- Black tammy style hat
- Black snood or scarf covering the lower part of his of face.
"This may have caused cyclists or motorists to move round it, and it is possible that anyone who was using a 'dashcam' or 'action camera' on a bike or motorbike has recorded it.
"The use of such devices is becoming more common, and I would appeal to those drivers or cyclists who passed down this road in either direction around 9.15pm and who have dashboard or handlebar cameras fitted to their vehicle or bike, to contact us so that any footage can be viewed.
"This was a violent act, and while his victim was not seriously injured, it is vital that we trace this man and bring him to justice. Police Scotland can be contacted on 101 or through Crimestoppers on 0800 555 111."