1. A method for determining a reachable area based on a road network, comprising: acquiring a location along a road and a road network map; generating a road node map based on the road network map; searching the road node map for a boundary point extending for a maximum travel distance starting from the acquired location, the boundary point including a selected point on a road between two adjacent road nodes exclusive on the road node map upon determining that one of the two adjacent road nodes extends beyond the maximum travel distance from the acquired location; and determining the reachable area based on the boundary point.