Starting Network Analysis > Common Analysis Parameters

CurbApproach

CurbApproach determines the possible direction when vehicle arrives and leaves network. When it comes to a general two-way road, it has one forward and one backward lane. If there is no safety island in the middle of the two-way road, the vehicle could freely change the lane. In such situation, the CurbApproach value will be 0. But if there is the safety island in the middle of the two-way road, we must decide if the flag is set on the forward lane or the backward one. If you want to reach the flag on the backward lane, we should drive on the current forward lane till the segment that allows drivers to U-turn, and make a left U-turn to the backward lane. Then drive to the position of the flag. Situations like this are called Curb problem. However, if the RoadWay of the segment where the flag is located is one-way road, Curb problem takes no effect. Please see the figure below.

To the system, the direction is decided based on the digitizing direction of the segment; that is, the From-node-to-To-node direction is the direction. Please note that the digitizing direction is only for recognition and classification but not exactly identical to the direction of road. The property is used to handle the CurbApproach problem by setting the relation between stop and the digitizing direction of the road. 0 represents no safety island in the middle of the road, so you can directly drive to the backward lane; 1 represents the position of the stop is in the right side of the road (FromNode-ToNode); 2 represents it is in the left side of the road(ToNode-FromNode). Through the property, we could know where the stop is located on the lane.