Everyone knows that Solomon Grundy was born on a Monday, had a few adventures and died on Saturday. But what about the Solomon curve?
The Solomon curve is a fascinating and initially counter-intuitive relationship between speed and the likelihood of collisions. It says that the absolute speed of your vehicle is not the most important determinant of how likely you are to be involved in a crash – the difference in speed between your vehicle and the average speed of the traffic is.
In other words, if everyone is speeding, it may be safer to speed rather than to stick to the speed limit. The explanation is in the number of manoeuvres that are required per unit of time or distance – overtaking, for instance. Thus, a slow tractor is serious hazard because it forces other vehicles into making a manoeuvre. Also, because manoeuvres often happen at slow speeds (like turning into a side road), a turning vehicle (an obvious hazard) has a lower speed than the average for the road.