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Help requested posted on 21st February 2020:

Design guide for single carriageway A road with 40mph speed limit

Understanding the following design guides; Design Manual for Roads and Bridges (DMRB) in the UK and Manual for Streets (DFS) in UK, when applied to a single carriageway A road with a 40mph speed limit. Which one do I use, or is it a combination of both?

William Bates

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Response posted on 21st February 2020 by:
Kate Carpenter

E: kate.carpenter@jacobs.com
T: 07920143940

Design guide for single carriageway A road with 40mph speed limit

Hi there, I'd say context is everything. In an urban area MfS may have relevance because it's about place and people. If your 40mph is a primary distributor or inter-town link, then the DMRB will dominate.

Do you have frontage development? Pedestrians crossing/alongside? cyclists on road? direct accesses to individual properties, or side roads? Do you have buses stopping and other access?

all of these will affect what the different reference docs will bring to your decisions. hope that helps a bit!


Response posted on 24th February 2020 by:
Charles Thompson

E: charles.thompson@novo55.com
T:

Design guide for single carriageway A road with 40mph speed limit

It depends. DMRB provides the standards for the trunk road network. Manual for streets is guidance and is only relevant on certain types of roads.

Your query relates to a single carriageway A road. If it is a trunk road, then DMRB.

If it is not a trunk road, it may be DMRB, but you need to check if the local highway authority has any local standards or guidance.

MfS provides guidance where the "movement" function of the road is lower than the "place" function, so I would say that usually an A class road wouldn't be MfS unless it is passing through a local centre.


Response posted on 27th February 2020 by:
Andrew Russ

E: andrew.russ@sweco.co.uk
T:

Design guide for single carriageway A road with 40mph speed limit

See also 'Manual for Streets 2 - Wider Application of the Principles' which can, quote; "be applied to busier streets and roads in both urban and rural locations up to, but not including, trunk roads". It includes, for example, suggestions for horizontal radii up to a design speed of 60kph.


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