Accident blackspot

It may have occurred for a variety of reasons, such as a sharp drop or corner in a straight road, so oncoming traffic is concealed, a hidden junction on a fast road, poor or concealed warning signs at a crossroads.

For some decades treatment of accident blackspots (e.g. by signage, speed restrictions, improving sightlines, straightening bends, or speed cameras) was a mainstay of road safety policy, but current thinking has it that the benefits of these interventions are often overstated.

Effects such as regression to the mean,[1] risk compensation[2] and accident migration combine to reduce the overall benefit.

In one notable experiment, a number of accident blackspots were "treated" with a null treatment—placement of a garden gnome, according to some reports.

Crash rates at these points were found to have decreased significantly in the following period,[citation needed] a finding which is taken as clear evidence supporting the theory of regression to the mean.