When you have just been involved in a car accident, everyone within range will be shaken up.
It can take minutes, even if no-one is hurt, to get around to deploying warning triangles upstream and downstream of the scene.
Today’s invention is a flexible, glass fibre mast, resembling an old fashioned CB radio aerial, which extends upwards, driven by a motor to a height of say 5m above a vehicle. It could be deployed manually when the hazard warning lights are activated or even automatically when the car suffered a sudden impact.
This would be topped by a flashing light to indicate an accident to oncoming vehicles in either direction.
A more advanced version would allow for several independent masts in case the vehicle had partly or wholly overturned.
(Their batteries might well be isolated from the main unit in order still to operate even if the car was badly damaged. Alternatively, the masts could be stored in a bowed configuration, requiring them only to be released to hoist the warning lamp(s)).