An accident blackspot is a term used in road safety management to denote a place where road traffic accidents have historically been concentrated. 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 cross-roads.

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 some cases it has been claimed that the end result is an increase in overall casualties. In one notable experiment, a number of accident blackspots were "treated" with a null treatment - placement of a garden gnome, according to some reports. Accident rates at these points were found to have decreased significantly in the following period, a finding which is taken as clear evidence supporting the theory of regression to the mean.

References

• Discussion of accident blackspots

Footnotes

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