Obstacles – poles, fences, tree branches etc. – on or near the cycle highway can pose a safety hazard by:
Creating a risk of collision between the bicycle or cyclist and the obstacle itself.
Increasing severity of injuries in case of fall or collision (hard objects, sharp edges etc.)
In case it is not possible to avoid obstacles altogether, they need to be well visible in advance and as “forgiving” as possible.
How can it be measured?
Clearance can be measured in several aspects:
Horizontal clearance on the cycle highway itself;
Horizontal clearance next to the cycle highway;
Vertical clearance above the cycle highway.
Minimum and recommended values
Ad 1. The clearance should provide enough space for bicycle width and safe margin of space for balancing or mistakes. The most typical value is 1.6 m. The subject is further elaborated in bollards and chicanes.
Ad 2. Most common bicycles are narrowest at the surface level, then need some more space for pedals, and at the height around 1 m above the surface even more for handlebars. Therefore, next to the cycle path surface there should be a strip of land clear of obstacles, so a cyclist does not hit it with a pedal or handlebar. The width of that strip might depend on the height of the obstacle. For example, the Flemish guidelines recommend minimum distance between cycle highway and:
a kerb of height up to 7 cm: 0.25 m
a kerb higher than 7 cm: 0.5 m
poles, lampposts, trees etc.: 0.75 m
walls, fences: 1.0 m
Ad 3. All analysed guidelines list 2.5 m as minimum vertical clearance, which provides around 0.5-0.75 m of space above the head of an average cyclist.
Guidelines/ standard
Horizontal clearance on cycle paths (e.g. between bollards)
Horizontal clearance next to cycle paths
Vertical clearance
Design Manual for Bicycle Traffic (CROW, NL)
1.6 m
0.25 - 1.0 m depending on obstacle type and height
2.5 m
Vademecum Fietsvoorzieningen (Flanders, B)
1.6-1.75 m
0.25 - 1.0 m depending on obstacle type and height
2.5 m
London Cycling Design Standards (UK)
0.25-0.45 m
Håndbog supercykelstier anlæg og planlægning (DK)
0.3 m
Réseau cyclable à haut niveau de service. Objectifs et principes d'aménagement (CEREMA, F)
0.25 - 1.5 m depending on obstacle height, point/linear character and visibility
Manual for the design of cyclepaths in Catalonia (E)
2.5 m
How is it related to other criteria?
Clearance is directly related to and often considered together with cycle path width.
Apart from direct risk, obstacles can also obstruct field of view, either of the surface ahead, or other road users approaching conflict points, therefore might be important for the criteria of design speed and safe crossings.
If it is not possible to eliminate the obstacles, they need to be well visible in advance, reinforcing the need for good lighting and markings.
Larger obstacles with insufficient clearance can create a social safety challenge, e.g. by providing hiding spots, making it impossible to escape or creating a claustrophobic impression.
Clearance and (lack of) obstacles 
Cycle highway F1 Mechelen – Antwerp. Note safe distance between the edge of cycle path and tunnel wall or fence. 