I am currently using QGIS 2.10.1. and I am not able to select any layer when trying to configure the Road Graph plugin. What should I do?
The QGIS Road Graph Plugin can not use Polyline with Z-values. I solved this problem by removing Z-Values from my polyline shapefile. In QGIS: right mouse click on the layer /Save as... under Geometry choose Geometry type and uncheck Include z-dimension. Here is also a solution with ArcGIS.
right click the road layer and press save as. Then under geometry choose LineString and uncheck z-dimension. The z-dimension may have caused the problem. then try again.