Section control is a method of speed enforcement involving a series of cameras installed over a stretch of road. An image and data are recorded for each vehicle as they enter and leave two points in the system (a section of road). The data are then used to calculate the average speed of the vehicle by dividing the distance between to points by the time taken to travel through them.

 Distance / Time = Average Speed

The average speed is then checked against the speed limit for that section, and if the average speed exceeds the speed limit, a fine or other sanction can be issued to the offender. In the late 1990s the Netherlands became the first country to implement this technology and a number of other countries are using it or have trialed it since (mostly in Europe, but also in Australia). 

The basis for introducing section control is that it encourages drivers to reduce their speed across an entire section of road and greater levels of behavior changes can therefore be obtained. There are indeed multiple cases documenting speed reductions across entire sections of roads, consequently having a positive impact on the number of collisions and casualties.