Thursday, 12 January 2017

The Strategic Road Network and the Redbridge Roundabout

A post from Liz Batten on the "I would Cycle in Southampton if.." Facebook Group on 09/01/17 alerted me to the existence of the wonderful document "INTERIM ADVICE NOTE 195/16:  CYCLE TRAFFIC AND THE STRATEGIC ROAD NETWORK" from Highways England.  Even more exciting was the offer of some associated e-learning.  What could be more fun? The opportunity to understand more about the rules and advice that traffic engineers work to, along with the opportunity to evaluate someone else's efforts at teaching on-line!

I spent every spare minute for the next couple of days working through the document and its e-learning - and I had also recently spent some time reading through Cycling UK's "Cycle-friendly design and planning" and Cyclenation's "Making Space for Cycling: A guide for new developments and street renewal" as I am currently preparing a blog post to discuss what would be the *minimum* acceptable standards of bike infrastructure that might kick start the expected Cycle Boom. So this was really interesting!

A screen from the Highways England e-learning module 4

As fas as the e-learning was concerned it was pretty amateur (although I am not sure I would be able to suggest how to do it better!).  The pedagogic strategy appeared to be "Read/watch/look at this, then we will ask you some questions to test your recall"  or occasionally "Here are some questions which will require you to go into the IAN document and find the answer".  But I admit that it did help me to find my way through some otherwise very tedious stuff.

I'll spare the reader the summary of the document (a later post)!), but its probably important to understand its context.  This "note" gives instructions to traffic engineers regarding the requirements for cycle infrastructure for ALL roads (the strategic road network) run by Highways England.  It uses vocabulary like "must" and "shall" - no options.  It does also contain some conditions under which engineers do not have to keep to these instructions. (Usually to do with "it would be impossible" or "we are too far down the implementation stage to change the plans now").  It would be interesting to do an FOI to find out how often these exceptions are used!

There is an issue of particular importance to Cycle Campaigners at the moment.

The Redbridge Roundabout (connecting Redbridge Road - A33 - A35,  to the M271) is part of the SRN.  Highways England, as we know form the recent Cycle Forum, is intending to try to increase traffic flow from the East (Southampton) onto the roundabout and north into the M271. To do this it will get rid of the lights, and it also wants to get rid of the pedestrian and cycle crossing across the feed roads.  See my possibly inaccurate sketch below...

Google Map scribbled on to show lights and Pedestrian / Cycle Crossing

Highways England have assured us that there is no problem as there is a subway under the South part of the Redbridge roundabout and a (cycle) bridge over the North-East part of the roundabout. You can just see them on the map above.

The pedestrian / cycle crossing is *much* used.  At present this does not effect traffic flow much as they can sync with the lights on the roundabout, but when these lights are taken away it will then be those nuisance pedestrians and cyclists (you know, the local residents who actually live here) who will slow down the progress of all that traffic that causes all the pollution in Southampton!        

Members of the of Southampton Cycle  Campaign present at the Southampton Cycle Forum were worried about these changes on many different levels but were presented with  a "fait acompli", and were told that there would be improvements to the underpass/bridge infrastructure.  When they attempted to question "what sort of improvements?" no answer was forthcoming ..

Now this is where IAN is important!  (Interim Advice Note 195/16), remember?  Section 2.5.1 and 2.5.2 cover the design requirements for "Underbridges" and Sections 2.5.3 - 2.5.7 cover the design requirements for "Overbridges".


The location and alignment of underbridges and their accesses shall be arrangedso that cyclists do not have long diversions from a direct line of travel. 
The length of the underbridge shall be minimised in order to maximise natural lightlevels, and the gradient of access ramps shall also be minimised (Figures 2.5.1and These design characteristics can help maximise forward visibilityand levels of natural light as well as the comfort (reference 2.2.1) of userstravelling through the underbridge. 

(so that's 3m + 1m margins at each wall- 5m wide as I understand it)

Overbridges for use by cycles and pedestrians only, are generally designed fortwo-way use and shall conform to the design parameters for cycle traffic, set outin Section 2.2. 
The width of a two-way cycle track shall be a minimum of 3.0m plus an additional0.5m margin clearance to each parapet (Table Where a footway isrequired, additional width shall be provided and the footway shall be separatedwith a kerb. 
(So thats 4m wide plus extra width if pedestrians are to be using it too)

Gradients on the approaches to underbridges and overbridges shall meet thecriteria set out in Section 2.2.9.
(This says stuff about trying to keep gradients under 3% and to keep the cycle route flowing.  It also says the maximum gradient should be 5% for 30m) 
The importance of helping the cycle design vehicle maintain momentum on rampsshall be considered and a ramp profile whereby the steepest gradient is at thebottom can reduce the effort needed to climb a ramp. 

So there you are! Thats the standards they are required to work to.  There are lots more things that may also apply (minimum radius of a cycle track might apply on the corner approaching the underbridge.

So the job of the Cycle Campaign and the Cycle Forum is to make sure that these standards (and the very laudable spirit of the IAN document) are adhered to.

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