By speed limit policy is meant the application of a general principle for setting speed limits.
Three such principles are compared in the report:
1. Optimal speed limits, by which the total societal costs per vehicle kilometre of travel are minimised;
2. Vision Zero speed limits, by which speed limits are based on biomechanical knowledge of human tolerance of impacts, and
3. An understandable speed limit system, by which speed limits are determined so that most road users find them reasonable and understand why different roads have different speed limits.
It is found that optimal speed limits are in most cases higher than current speed limits and will therefore lead to an increase in the number of killed or injured road users.
Vision Zero speed limits are lower than some of the current speed limits and will reduce the number of killed or injured road users.
An understandable speed limit system implies speed limits that are close to current speed limits, but would allow for selective changes, in particular when offered as jointly lowering speed limits on some roads and raising them on other roads, so that the reasons for different speed limits can be made clear.
An understandable speed limit system will not be associated with changes in the number of killed or injured road users.
The report is written in Norwegian, but you can read an English summary.