I am trying to draw a path on roads and follow some given points.I am using Google Directions API to follow the roads.I put some markers on roads and link these points with polylines.I need to follow the red line but it follows and draws blue lines.How can I ensure this?
Verify if it is a road at all by zooming in. Also Make sure that u can tread in that direction in the road.Sometimes roads are one way, So google automatically chalks out an alternative path. Hope this helps.
来源：https://stackoverflow.com/questions/26161459/how-to-ensure-that-follow-specific-google-map-road-while-using-google-map-api