Route Match Extension API algorithms assume that the route is taken on the official road network obeying legal restrictions for the vehicle type. The computed route includes illegal paths only if the GPS trace apparently proves that the driver ignored a one-way system, a turn or an access restriction, and may also include a corresponding warning. Hence it is possible to find out legal violations using this service if they are very obvious from the trace points.
It is important to select the correct vehicle type, if is known, or otherwise the most probable one. A car trace matched in pedestrian mode would tend to ignore one-way systems and favor footpaths, but avoid motorways, whereas a pedestrian trace matched in car mode would try to avoid footpaths and other illegal thoroughfares unless very obvious. So, especially for sparse traces or bad point accuracy, the matching quality is worse if the vehicle type is inappropriate.
In summary, Route Match Extension API can determine where a driver most probably violated rules with regard to one-way systems, turn restrictions or access restrictions, and the matching algorithm stays on the safe side, giving preferrence to legal paths unless obvious.
Time-dependent legal restrictions are considered correctly, if the trace contains time stamps, otherwise they are considered as time independent.
Legal speed limits are not considered while constructing the most probable route, that is a road section is not avoided just because the GPS trace suggests that the driver would have speeded when traveling on it. Hence, Route Match Extension API can be used to determine where the driver was speeding.
If a use case requires a strictly legal route, the request parameter
&legal specifies which illegal maneuvers to avoid, regardless whether the trace obviously reflects such violations.