Swept path analysis: what the highway officer checks

A swept path analysis is a set of drawings showing the area a chosen vehicle occupies as it makes a defined manoeuvre, and the highway officer checking it is asking three questions. Is that the right vehicle for this development. Does the envelope clear every kerb, wall, column and parked car. Would a driver actually perform that manoeuvre without a banksman and three shunts.

Most rejected tracking drawings fail the first or the third question rather than the second. The geometry is usually fine. What is missing is a justification for the vehicle chosen, or a manoeuvre that only works because the modeller allowed a 20 point turn in a courtyard.

Choosing the design vehicle and saying why

The vehicle governs everything downstream, so name it on the drawing with its overall length, width, wheelbase and turning radius, and say where the dimensions came from.

For a residential scheme the usual set is a private car for every space and turning head, the collection authority's refuse vehicle for the waste route, and a fire appliance where the layout requires it. Do not take refuse vehicle dimensions from a generic library. Waste fleets differ between authorities, and a narrow-access vehicle in one borough is replaced by a full-size rigid in the next. Ring the waste service and ask.

For commercial and industrial schemes the design vehicle follows the operator. A distribution unit is tracked for a 16.5 metre articulated vehicle because that is the legal maximum for general haulage in the United Kingdom. A trade counter unit is often tracked for a rigid and a transit van instead, and stating why the larger vehicle will not attend is part of the evidence rather than an omission.

Where the site is on or near the strategic road network, the design vehicle and the standards come from the Design Manual for Roads and Bridges rather than from residential guidance, and National Highways becomes a consultee.

The envelope, the body overhang and the margin

Tracking software produces two things: the path swept by the wheels, and the path swept by the vehicle body. The body path is wider at the front overhang on a car and dramatically wider at the rear overhang on a long rigid, and it is the body envelope that has to clear obstructions.

Add the clearance margin the highway authority requires between that envelope and anything solid. Half a metre is what most authorities expect for low speed manoeuvres, and some ask for more where the obstruction is a wall or a structural column rather than a kerb.

Track at a low manoeuvring speed. A path generated at 15 kilometres per hour understates the area a driver needs at walking pace with the wheel on full lock.

Model what is actually there. Parked cars in bays, bin presentation points on collection day, street trees at maturity, bollards, lighting columns and the pavement build-outs the council has just installed all belong on the drawing. A tracking exercise against an empty street answers nothing.

Where overrun is acceptable

Overrun is a design decision, not an accident to be shown in a lighter colour.

Inside a private site, an overrun strip at the inside of a tight bend, built to take axle loads and finished flush or with a bullnose kerb, is normal and accepted. So is a shared surface where vehicles and pedestrians mix by design and speeds are very low.

What officers refuse is overrun of a footway, a verge, a cycle track, a parking bay in use, or the opposing carriageway on a public road. Those are places people and vehicles are expected to be, and a layout that needs them is a layout that will produce conflict every collection day.

If the drawing shows overrun, annotate it: what surface, what construction, and why it is acceptable there. Silence reads as an error rather than a decision.

Emergency and refuse access

Approved Document B sets the access dimensions for fire service vehicles, covering minimum road and gateway widths, turning circle diameters, clearance heights and carrying capacity, and it distinguishes a pump appliance from a high reach appliance. Those dimensions, plus the maximum distance from a vehicle access point to points within a dwelling, drive the layout of any scheme where houses sit behind a frontage or a block has a single approach.

Track the appliance to the point the standard requires it to reach, not simply into the site. And take the carrying capacity seriously on schemes with basements, podiums or attenuation crates beneath a drive, because the structural check belongs with the tracking drawing.

Refuse access has a parallel logic. Approved Document H sets expectations for the distance a householder carries waste to a store and the distance a collector carries a bin to the vehicle. Where those are met at the frontage, the vehicle need not enter at all, which is usually the better answer. Where it must enter, it should leave in forward gear, and a reversing manoeuvre of any length will draw an objection from the waste service before the highway officer sees it.

Failures that repeat on small residential layouts

The same handful of problems account for most of the tracking work redone at validation stage.

• A turning head sized from a standard detail rather than tracked, which works for a car and not for the refuse vehicle.
• A garage or parking space that cannot be entered in one movement because the aisle width was set by the plan grid.
• Gate posts or a gateway narrower than the vehicle envelope plus margin, often introduced by the landscape drawing after the transport drawing was signed off.
• Bin stores placed at the back of a plot with a carry distance nobody measured.
• A drive width that meets the standard on the straight and pinches at the bend where two vehicles were assumed to pass.
• Construction vehicles never tracked at all, which reappears as a condition requiring a Construction Traffic Management Plan before work starts.

Drawing it so it can be checked

Presentation decides how long the check takes. Use a recognised scale and state it, put a north point on, and give each drawing a title that names the vehicle and the manoeuvre.

Show entry and exit as separate passes on separate sheets rather than overlaying four movements in one colour soup. Distinguish the wheel path from the body envelope in the legend. Put the vehicle dimensions and turning radius in a box on the sheet so the officer does not have to open a separate document.

Where the manoeuvre involves a shunt, show each leg and number them. Two movements is normal for a delivery bay. Five is a sign the layout needs changing.

On larger schemes the tracking drawings sit inside a Transport Statement or a Transport Assessment and are cross-referenced from the access chapter, which is the arrangement highway officers prefer, because the narrative explains what the drawings show. You can see the whole set of transport and highways report types by category if you are assembling a pack from scratch.

Tracking work is a technical exercise and councils usually expect a suitably qualified author, so treat any AI-assisted draft as the narrative around the drawings rather than as the drawings themselves. Enter your postcode on PlanScope to see which transport documents your scheme is likely to need.

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