The Sustainable Safety vision has led to twelve general functional requirements for a safe road network, safe routes and a safe road design [2].
At the road network level, the requirements are:
1. Make residential areas as large as possible and contiguous.
2. Make sure that the amount of travel on relatively unsafe roads is as small as possible.
3. Make journeys as short as possible.
4. Make sure that the concepts 'shortest path' and 'safest path' coincide.
Network-level requirements ensure that residential areas are almost exclusively used by traffic that has its destination or origin there. Pedestrians and cyclists in residential areas therefore encounter less motorised traffic; this increases safety [3]. Exposure to hazards and to traffic in general diminishes when requirements 2, 3 and 4 are complied with.
At route level:
5. Prevent search behaviour.
6. Make road categories as predictable as possible.
7. Limit the number of safety solutions and make them more uniform.
These route-level requirements allow traffic to use the roads as much as possible in a way for which they were designed. Road design is tailored to the intended use; it increases safety especially if actual use does not deviate too much from intended use.
At the level of road design:
8. Prevent conflicts with oncoming traffic.
9. Prevent conflicts with crossing and traversing traffic.
10. Separate traffic types.
11. Reduce the speed at potential conflict points.
12. Prevent obstacles along the carriageway.
The requirements of the road design are intended to prevent crashes and to reduce the severity of the consequences of unavoidable crashes. By means of these requirements, possible conflicts between vehicles are prevented to a maximum extent, for example by separating driving directions [4].
