Use Streets Not Allowed For Cars
Bicycle (Beta version) routing uses all roads that are open for pedestrians. This includes pedestrian-only roads, and road segments that require traversing a one-way road opposite the allowed direction of travel. When a road is not open for driving in the travel direction, the routing algorithm assumes that the user must walk the bicycle, and therefore it uses the pedestrian walking speed for such segments. As a special exception to this rule, pedestrian segments located in parks are assumed to be open for bicycles, so full bicycle speed is used there. Generally, such walk-only segments are used in bicycle routing only when they provide a big shortcut, or when a waypoint is located on such a segment.

https://route.ls.hereapi.com/routing/7.2/calculateroute.json
?apiKey={YOUR_API_KEY}
&waypoint0=geo!52.51870244007625,13.424562549544333
&waypoint1=geo!52.519537421264,13.424157659963328
&mode=fastest;bicycle