The amount of driving in the speed range just over the limit is explained by the design of the ISA system, which gave the drivers some margin before cutting in. A similar pattern can be seen in Figure 6.10, which shows the speed distribution on the 70 mph (112 km/h) roads which are mainly motorways. Probably the most comprehensive set of calculations is that from the trials conducted in the ISA-UK project. The prediction is that an advisory ISA in general use would save 3% of injury accidents and an intervening ISA would save 12% of injury accidents and 20% of fatal accidents.