Designing estate roads to Manual for Streets

Ask ten consultants what Manual for Streets requires and you will get ten answers, most of which are not in it. It is the most cited and most misquoted document in UK residential layout design. This guide sets out what it says, what it declines to specify, and how to test a layout against it.

What Manual for Streets is, and what it is not

Manual for Streets was published by the Department for Transport on 29 March 2007. Its own Status and Application page is unambiguous: MfS "comprises technical guidance and does not set out any new policy or legal requirements". It is guidance, not a standard: nothing in it is mandatory, and a finding against MfS is an argument, not a failure.

Three scope limits matter. MfS applies formally only in England and Wales. It does not apply to trunk roads, which remain the Design Manual for Roads and Bridges. And it superseded Design Bulletin 32 and its companion guide Places, Streets and Movement, both withdrawn in England and Wales — DB32 geometry surviving in a local design guide is a sign it has not been reviewed since 2007.

Manual for Streets 2 (2010), prepared for the Chartered Institution of Highways and Transportation and endorsed by the DfT, extends the principles to busier streets and non-trunk roads and states plainly that it "does not supersede MfS1". A consolidated update by DfT and CIHT was still unpublished when this page was written. Scotland has its own Designing Streets (2010), a policy statement rather than guidance.

Adoption is the local authority's decision

Nothing in MfS obliges anyone to adopt anything: adoption runs on section 38 of the Highways Act 1980, and the highway authority applies its own published design guide. MfS 1.4.5 recommends authorities review their standards to embrace its principles; many have not. The document that governs your scheme is the local highway authority's design guide, and MfS is what you argue from when that guide produces a street nobody wants.

The shift the document is really about

MfS 1.6.1 puts pedestrians at the top of the user hierarchy, moves away from hierarchies of standard road types based on traffic flows or buildings served, and derives street character types from each street's place and movement function; 7.4.2 adds a maximum design speed of 20 mph as a normal objective. If a design guide bands streets by dwelling count and hands you a width, it is doing the thing MfS moved away from.

Carriageway and footway width

MfS Figure 7.1 illustrates four widths — 2.75 m, 4.1 m, 4.8 m and 5.5 m — under a caption routinely cropped off: they "are not necessarily recommendations". MfS sets no minimum carriageway width. Paragraph 7.2.2 instead lists what width should answer to: traffic volume and composition, pedestrian activity, carriageway parking, street curvature and design speed.

Where it does give numbers they are constraints, not targets: 7.2.3 says that in single-lane working sections widths between 2.75 m and 3.25 m should be avoided because drivers squeeze past cyclists, and that below 3.7 m the Fire Safety Officer should be consulted. On refuse, 6.8.7 reports BS 5906:2005 noting vehicles around 11.6 m long with a 20.3 m turning circle and recommending a 5 m minimum street width. The familiar 5.5 m is a local adoption standard, not an MfS one.

For footways, 6.3.22 is the paragraph to quote: there is no maximum width, and in lightly used streets with a purely residential function "the minimum unobstructed width for pedestrians should generally be 2 m", more near schools and shops. Note unobstructed: columns, bins and signs come out of it. MfS points to Inclusive Mobility for detail.

Visibility: splays, forward visibility and the speed you design to

MfS recalculated stopping sight distance on a 1.5 second perception-reaction time and 0.45g deceleration (7.5.7), well short of DB32. Table 7.1 gives the results; use the row adjusted for bonnet length, since 7.6.4 adds 2.4 m for the driver sitting behind the front of the car: 25 m at 32 kph (20 mph), 33 m at 40 kph (25 mph) and 43 m at 48 kph (30 mph).

Paragraph 7.5.1 frames this in terms of 85th percentile speeds, not posted limits, and 7.4.8 warns that a speed limit is not an indication of the appropriate speed to drive at. If you are joining an existing road, measure it. MfS2 10.1 carries the same method onto busier, non-residential streets, up to 60 kph (37 mph).

At junctions the X distance is 2.4 m, which 7.7.6 calls a reasonable maximum between the car's front and the driver's eye; 7.7.7 allows 2 m in very lightly trafficked, slow-speed situations. Paragraph 7.7.8 is explicit that X beyond 2.4 m "is not generally required in built-up areas", and 7.7.9 cites TRL Report 184 finding accident risk increased with greater minor-road sight distance; Y comes from Table 7.1. Forward visibility equals the minimum SSD along the centreline of the inner traffic lane (7.8.1), and 7.8.2 notes that reducing it deliberately can be the right way to hold speeds down.

Junction spacing and corner radii: numbers MfS does not give

MfS sets no minimum junction spacing. Paragraph 7.3.17 says spacing should follow the block size appropriate to the development, and 7.3.18 that more frequent junctions improve permeability and, on MfS's own research, need not increase accidents. A figure like 30 m quoted at you as MfS comes from a local guide or DB32.

There is no corner radius figure either, and that is deliberate. Paragraph 6.3.12 asks for small radii so pedestrians are not pushed off their desire line; 6.3.13 accepts large vehicles may then need the full carriageway width and says swept-path analysis determines the minimum, with the footway strengthened locally for overrun. The answer to "what radius?" under MfS is a tracking drawing, not a table — the discipline set out in swept-path analysis for UK housing, and behind car park layouts.

Straight runs, cul-de-sacs and the bin lorry

Paragraph 7.4.3 is the source of the straight-length rule: traffic-calming evidence suggests speed-controlling features are needed at intervals of no more than 70 m to hold 20 mph, so "straight and uninterrupted links should therefore be limited to around 70 m".

For cul-de-sacs, 6.8.3 asks for a turning area where the dead end runs longer than 20 m. On reversing, 6.8.8 reports BS 5906:2005 recommending a maximum reversing distance of 12 m — authorities differ, some applying 10 m, and the collection authority decides. Paragraph 6.8.11 reports the same standard on collectors moving bins no more than 15 m (two-wheeled) and 10 m (four-wheeled); those legs are covered in the refuse vehicle access guide. And 6.8.2 is worth remembering: a well-connected network avoids reversing altogether.

Checking a layout before you submit it

• Get the local design guide first and list every place it departs from MfS.
• Fix the design speed and measure the 85th percentile on any road you join. Splay Y follows from that, not from the sign.
• Prove junctions by tracking, using the refuse vehicle the collection authority actually runs.
• Test the walking network, not just the driving one. A layout can be adoptable and still make neighbours walk 400 m to reach a fence.
• Record the reasoning. A departure you can explain usually survives; one you cannot usually does not.

What Airship Site Designer checks

Airship Site Designer ships four standards presets — Manual for Streets, Durham-style, Compact infill and an editable custom set — and runs ten geometry checks, from bend radii and widths to junction spacing, visibility splays, turning spaces and swept path.

On the Manual for Streets preset, some values track the document and some do not. The splay X of 2.4 m and the lightly-trafficked 2.0 m follow 7.7.6 and 7.7.7; the Y values of 25 m, 33 m and 43 m are Table 7.1's bonnet-adjusted row; the 20 m dead-end trigger follows 6.8.3. The 25 m junction spacing, 15 m bend radius, 4.8 m carriageway minimum and 60 m straight-run limit are ours — MfS sets none of them.

The swept-path tool drives a tractrix model along a route you draw, with vehicles from an 11.2 m refuse lorry to the 18.55 m longer semi-trailer. A separate design review adds good-practice findings, each labelled with its basis and whether the threshold is sourced or ours. Layouts export as layered DXF. The full designer workflow and the help centre cover the rest.