Travellers can reach a destination easily and fast by using navigation systems and route planners, which are often able to dynamically adjust a route according to changing traffic conditions. However, navigation systems primarily focus on the interests of the individual road user. Too often, the impact on safety and liveability along the suggested routes is neglected. Policy makers aim at a sustainable use of the road network with a focus on public interest, rather than on the individual profit of a navigation system user. To avoid improper use of the road network, many countries have developed a functional road categorisation. In the Flanders region this was defined in the Flemish Spatial Structure Plan (RSV 1997).
This research examines to what extent the route planners induce improper road use. Several route planners are used to calculate routes between origins/destinations relations. Between each relation exists a preferred sustainable route. The routes suggested by route planners are compared to the corresponding preferred route, after which the road classification usage of route planners can be evaluated. Routes are calculated under normal (static) and congested (dynamic) traffic conditions. The in–depth analysis of this research indicates an over–(mis) use of local, in particular in a congested road network. It is concluded that the implementation of the Flemish road categorisation in route planning has the potential to stimulate a more sustainable route choice, but does not provide a sustainable alternative route if congestion occurs. The categorisation system itself needs a critical review, especially in congested areas.

route planning, dynamic route planning, navigations systmes, traffic liveability, road categorisation