As our cities are putting more emphasis on walking and cycling, they are building more footbridges. I am told bridges are often a lot cheaper to build than tunnels. Also, I would have thought people feel safer crossing an open bridge than entering a long subway.
River crossings can be beautiful at night and some of Britain’s most famous landmarks are bridges. As such, they need special attention when designing the lighting – and here are three ways to do it. All have their pros and cons, and they depend on other factors such as the way the bridge is built, its dimensions and its location.
Most lighting recommendations are expressed as horizontal illuminance on the pavement/deck but, as in a pedestrian shopping precinct, the vertical illumination is equally important. People must to be able to see and recognise others from a distance. As a starting point, you should refer to BS 5489 and then use your professional judgement as to whether to deviate from the recommendations.
Unless there is a good reason otherwise, you should use white light with good colour rendering. BS 5489 requires a CRI greater than 60, but most LEDs in these applications will have CRIs that exceed 80.
Be wary of using coloured light if your bridge passes over a railway or navigable river. You do not want to your lighting to be confused with any signalling.
Our footbridge is 4m wide and 40m long. The handrail is 1.2m high.
DW Windsor has a long pedigree in making good quality streetlighting and the Kirium Mini has been specifically designed for applications such as residential roads, paths and cycleways. Streetlighting engineers refer to these areas as P Class.
Local authority schemes often use 5 or 6m columns on footpaths, but here, the luminaires are mounted on 4m columns to keep them in scale with the bridge. The big advantage of this type of scheme is that it is easy to achieve good vertical illumination and there are far fewer lighting positions than the other options. Using columns means the luminaires are kept out of harm’s way.
Another advantage of this solution is that it has the lowest energy consumption per length of footbridge.
The reason that not all footbridges are lit this way is that using columns is not always possible. This can be because there are structural and mounting problems or simply a matter of aesthetics and scale.
- Luminaires DW Windsor Kirium Mini
- Optical control Lenses
- Arrangement Single sided on 4m column
- Average horizontal illuminance 30 lx
- Electrical load 2.7W per linear metre
- Pros Good vertical illumination at height
- Cons Columns can detract from appearance of bridge
This may be my favourite way to light a footbridge. The Garda is a complete stainless steel handrail with a line of LEDs inside. It is so good it won a Lux Award in 2011. DW Windsor offers a symmetrical light distribution for situations in which there is a central handrail. Alternatively, there is an asymmetric distribution and the handrails are mounted on the sides.
For this particular application, I have mounted the LEDs on both sides but it would work almost as well with a single-sided arrangement. There is plenty of horizontal illumination and the LEDs are hidden from view. Any obstacles on the path are clearly seen.
There is plenty of illumination on the deck, so light is reflected upwards to light people’s faces.
It’s neat, unobtrusive and vandal resistant – what’s not to like?
- Luminaires DW Windsor Garda handrail
- Optical control Lenses
- Arrangement Both sides
- Average horizontal illuminance 50 lx
- Electrical load 6.8W per linear metre (equivalent to 4W per linear metre at 30 lx)
- Pros Uniform lighting and inconspicuous
- Cons Works best with pale decking
Lighting a public open space with uplights recessed in the ground is quite common. One reason is that, by day, the luminaires are almost invisible and at night you just see lines of light. It gives a very clean appearance.
Another reason is that cabling is relatively simple. The cables and fixings are out of sight and you don’t have to worry about the bend radius as the cable enters a narrow column or handrail post.
The line of luminaires matches that of the handrail sections and produces a pleasing pattern at night.
One possible disadvantage of this method is that no light shines directly on the deck or pavement. We have overcome this by directing the light from the Malo LED strip on to the underside of the handrail. This reflects light down on the deck. Using a wide beam means the upward-facing light also illuminates the pedestrians full height.
- Luminaires DW Windsor Malo LED strip recessed in deck
- Optical control Lenses
- Arrangement Recessed in deck
- Average horizontal illuminance N/A, but some reflected from handrail
- Electrical load 14W per linear metre
- Pros Good visual guidance
- Cons Works best with solid sides to footbridge