Travel Time by ask Google with http

Hy
I trie to find out the tryffic on my route to work. For that i use the http request by google:

https://maps.googleapis.com/maps/api/directions/json?origin="my place"&destination="my work"&KEY&departure_time=now

But the receved time: "duration_in_traffic.text" seems alway be the same.

Do someone habe experiance with this feature ?