Google Directions Api returning 0 routes

Question

We are calling the google directions api to calculate round trip values. In general it works perfectly. I have however come across a use case where it fails to come up with

Answer 1

When you use via: prefix (no stopover), it adds some additional restrictions. Particularly the U-turn maneuver is not allowed, the route must go straight forward through waypoint. If this is impossible the Directions service will return ZERO_RESULTS.

To check this hypothesis I created exactly the same request, but with stopover (without via: prefix). You can see the result in the Directions calculator:

https://directionsdebug.firebaseapp.com/?origin=-33.92873%2C18.458879&destination=-33.92873%2C18.458879&waypoints=-33.9403%2C18.666731

Indeed, you should do the U-Turn in -33.9403,18.666731 (marker B) and this is the reason for ZERO_RESULTS when you try to create a route without stopovers.

This is also confirmed in the official documentation:

Caution: Using the via: prefix to avoid stopovers results in directions that are very strict in their interpretation of the waypoint. This may result in severe detours on the route or ZERO_RESULTS in the response status code if the Google Maps Directions API is unable to create directions through that point.

https://developers.google.com/maps/documentation/directions/intro#Waypoints

I hope this explains your doubt!