- url: 'http://{s}.tile.thunderforest.com/transport/{z}/{x}/{y}.png',
- attribution: "Tiles courtesy of <a href='http://www.thunderforest.com/' target='_blank'>Andy Allan</a>"
+ url: document.location.protocol === 'https:' ?
+ 'https://{s}.tile.thunderforest.com/transport/{z}/{x}/{y}.png?apikey={apikey}' :
+ 'http://{s}.tile.thunderforest.com/transport/{z}/{x}/{y}.png?apikey={apikey}',
+ attribution: '© <a href="http://www.openstreetmap.org/copyright" target="_blank">OpenStreetMap</a> contributors. Tiles courtesy of <a href="http://www.thunderforest.com/" target="_blank">Andy Allan</a>'