Tunnels and bridges

• Het Groentje bridge on the F325 cycle highway in Nijmegen (Netherlands).
• The bridge along the river Vrouwvliet and under two railroad bridges on cycle highway F1 north of Mechelen (Belgium).

Bicycle bridges can be spectacular landmarks that help to create awareness and promote the route.  On the other hand, bicycle tunnels:

• usually require the cyclists to overcome smaller height differences than bridges, because the clearance required for car or rail traffic (4.5 m and more) is higher than for bicycles (2.5 m);
• allow the cyclists to utilise the speed gained on descent to facilitate ascending;
• may offer some shelter from wind and rain.

However, bicycle tunnels are often a matter of concern in terms of social safety. Therefore, special care needs to be taken in the design phase to ensure that people feel that the tunnel is a safe place.

Tips and tricks – tunnels

• Eisenhower tunnel on the F325 cycle highway, Netherlands. Straight approach, good visibility and smooth curves at the...
• A15 tunnel on the F325 cycle highway, Netherlands. Walls leaning outward help to create a roomy feeling.

• Cycling tunnel does not need to be as deep as road tunnel, even if placed next to it. The clearance required for bicycles is usually around 2 m less than for car traffic. The allows for lower gradient and/or shorter approach ramp.
• Let the cyclists see all the way through to the other side. To achieve this, it might be necessary to slightly elevate the road (or other obstacle) to reduce the depth of the tunnel.
• Make the approach to the tunnel straight from both sides. Make sure there are no dark corners obscured from view. 
• Let the cyclists utilise the speed they gain on the way down to get out of the tunnel quickly. 
• Walls leaning outwards helps to create a roomy feeling.
• Consider making “windows” in the roof of the tunnel to allow daylight to enter sections of the tunnel.
• Smooth curves in the construction elements instead of the traditional straight angles can also increase the perception of social safety.

Tips and tricks - bridges

• Snelbinder bridge on the F325 cycle highway in Nijmegen, Netherlands. The railings bend outwards and have widest...
• The crossing at the bottom of the ramp leading from het Groentje cycling bridge (Nijmegen, Netherlands) gives priority...

• Make the slopes gentle.
• Avoid crossings with no priority or tight curves at the bottom of the ramps leading to the bridge. Apply increased design speed on the ramps and 50-100 m after, do not make the cyclists coming from the bridge brake and waste energy.
• Bend the railings outwards and make them have widest clearance at the level of typical bicycle handlebar. This will reduce the risk of collision and provide more space without increasing the width of the bridge itself.

Mistakes to avoid

• Sharp turn and obligation to give way at the bottom of the ramp.
• This might have seemed like a solution for the risk of collisions with cars, but does not guarantee social safety....

• Crossings with no priority or tight curves at the bottom of the ramps (further discussed in slopes and gradients).
• Ramps curving downhill to the right (in right-hand traffic).
• Dark tunnels in desolate places.
• Sharp curves, restricting visibility, at tunnel entrances