An approach is provided for identifying special areas with significant vehicle activities that do not represent established roads (e.g., construction areas). The approach involves, for example, retrieving probe data collected from sensors of probe devices traveling within a geographic area including at least one geographic partition. The approach also involves dividing each of the at least one geographic partition into grid cells. The approach further involves, for each grid cell, detecting directional groupings of the probe data. The directional groupings comprise probes of the probe data that share a respective common direction of travel. The approach further involves detecting a set of grid cells with a count of the directional groupings that is above a count threshold. The approach further involves designating an area associated with the set of grid cells as an unconstrained area or a sub-area of the unconstrained area. The approach further involves providing the unconstrained area, the sub-area, or a combination thereof as a mapping data output.