Google Maps has a Bicycling overlay that can help you. It does have a few indication that states what type of road you have :
* Trails
* Bicycle-friendly roads
* **Dedicated lanes**
* Dirt/unpaved trails
So you might check those dedicated lanes.
An other option would be to use Strava's Global Heatmap where you can see where people are cycling the most. You can't really see what you want exactly (dedicated lanes), but coupled with Google's map, I find it's a good start to plan a ride.