The next step was to make note of all the parameters of our given site.
We firstly researched the required dimensions, starting with the width needed on the decking to accommodate all users. The Department for Transport suggest a minimum width of 3 metres for a two-way cycle path, and 2 metres for a pedestrian path with the view to accommodating wheelchair users, as laid out in Local Transport Note 1/12 (page 40).
Secondly, we looked at the height needed to successfully clear all vehicular traffic. The tallest vehicle which uses Lewes Road is the double-decker bus, which stands at approx. 4.3 metres tall. However, the Highways Agency requires a headroom of 5.7 metres for footbridges. Part 2.8 of Approved Document K states that ramps should have a maximum gradient of 1:12, meaning the subsequent ramp must be at least 68.4 metres.
Next, we had a look at external influences, the main one being the tree obstructions. In an attempt to find out if any of the trees in question were protected, we searched the Brighton & Hove Council website for Tree Preservation Orders. Unfortunately, the council charge over £30 to release the documents, so we were unable to acquire the necessary information.
A key consideration,as briefly mentioned on the opening day, is the redevelopment of Preston Barracks. As this is due to form an addition part of the University of Brighton’s Mouslecoomb campus, it is highly likely that the client is hoping to use the new footbridge to integrate this land with the existing university buildings. Our research (eventually) led us to the official website for the redevelopment, Momentum for Lewes Road (www.momentumlewesroad.com). Here we found the ‘Masterplan’, the proposed layout of the renovated area:
The new buildings situated in what is currently Mithras Car park meant that we were not able to stretch the bridge from the steps immediately outside of Mithras House, which would have cleared the road height by around 7 metres. Instead, we would have to use some land much nearer to, if not part of, the existing pathway. Another observation we made is that the renovators plan on removing some trees in order to install a footbridge of their own, which implies that we wouldn’t have a problem removing any obstructing trees for our bridge.
Resources:
DMRB Volume 6 Section 1 Part 2 – TD 27/05 – Cross Sections and Headrooms: http://www.standardsforhighways.co.uk/ha/standards/dmrb/vol6/section1/td2705.pdf
Momentum Lewes Road Masterplan: http://www.momentumlewesroad.com/plans/masterplan-2/
Tree Preservation Orders (Brighton and Hove City Council): http://www.brighton-hove.gov.uk/content/leisure-and-libraries/parks-and-green-spaces/tree-preservation-orders
Building Regulations 2010: Approved Document K: Protection from falling, collision and impact