text: Title: Transit and traffic layers
  Body: Google maps allows showing the current traffic and the transit routes. See [this](https://developers.google.com/maps/documentation/javascript/trafficlayer) for examples.
  
  Anyone interested in adding this should follow the bicyling layer.
  
   - [X] transit layer
   - [x] traffic layer
   - [x] transit layer not downloadable?
   - [x] amend tutorial section on bicycling to also talk about transit and traffic layers.