Choosing the design vehicle for swept path analysis

The design vehicle is the largest vehicle that will use an access or street regularly, and it sets the corner radii, carriageway widths and turning provision for the whole layout. Swept path analysis design vehicle selection is therefore a decision about the site, made before the tracking software is opened, and justified in a sentence the highway officer can test.

Pick too small a vehicle and the layout fails on the first refuse collection. Pick the largest vehicle that could conceivably arrive and the streets become wide, fast and hostile to everyone on foot, which the same highway officer will also object to.

Regular and occasional vehicles are different questions

Street design guidance draws a distinction that resolves most disagreements.

The design vehicle is the one that uses the street routinely. On a residential street that is almost always the refuse vehicle, because it visits every week and has to reach every dwelling. On a small industrial estate it may be a rigid delivery vehicle. On a retail unit with its own service yard it is whatever the occupier's distribution contract specifies.

The check vehicle is the one that comes occasionally: a pantechnicon on moving day, an articulated delivery two or three times a year, a fire appliance. For these, the layout does not need to accommodate the movement within the normal running lanes. It needs to show the movement is possible, using the full width of the carriageway, an overrun area or a reversing manoeuvre.

Stating which category each vehicle falls into, and why, is what turns a set of drawings into an argument. Officers reject tracking far more often for missing justification than for a failed swept path.

Getting the refuse vehicle right

The refuse vehicle is the one that decides residential layouts, and generic library vehicles are the wrong starting point. Waste collection fleets differ between authorities, and a vehicle chosen from a national default can be shorter or longer than the one that will actually arrive.

Ask the authority's waste service for the dimensions of the vehicle serving the area, including overall length, wheelbase, width over mirrors and turning circle. Many highway authorities name a vehicle in their design standards and expect tracking against that one. Where they do, use it whatever the software default offers.

Two operational constraints travel with the vehicle and matter as much as the geometry. The distance a crew is expected to drag a bin from its storage point to the collection point is limited, and the distance a vehicle is expected to reverse is limited too. Building regulations guidance on waste storage sets out carry distances, and most waste services publish their own reversing policy. A layout that tracks perfectly but requires a 40 metre reverse will still be refused.

How much clearance to allow

A swept path drawing that touches the kerb line is a drawing of a collision.

Allow a margin between the swept envelope and any kerb, wall, column, tree pit or parked vehicle. Around half a metre is common for routine movements on a street, with less accepted for occasional manoeuvres in a controlled yard. The authority's own standard governs where it states one.

The margin has to be applied to the widest part of the envelope, which is usually the front overhang on the outside of the turn rather than the rear wheels. Mirror swing is a separate check against walls, columns and boundary fences at mirror height, and it is the check that catches out narrow gated accesses.

Allow for parked vehicles where parking is unrestricted. Tracking through an empty street that will contain parked cars within a month is a familiar way to lose a highway objection later.

Overrun areas instead of wider radii

Widening a junction radius to suit an occasional vehicle speeds up every turn made by every other vehicle, which is bad for pedestrians and cyclists. An overrun area does the same job without that effect.

A contrasting surface, flush or nearly flush, set outside the running lane and built to take the load, lets an occasional large vehicle cross the corner while keeping the effective radius tight for cars. It is a standard technique in residential street design and is usually accepted where the vehicle using it really is occasional.

Two details make it work. The construction has to carry the axle loads, so a decorative surface on a shallow base fails within a year. And the area has to be distinguishable enough that drivers do not treat it as carriageway, without becoming a trip hazard for people crossing.

Steering assumptions and where the model misleads

Tracking software models a vehicle turning at a low speed with the steering wheel held at a chosen lock. Change the speed or the lock and the envelope changes, which is why two consultants can produce different results for the same junction and the same vehicle.

State the assumptions. A slow manoeuvre with full lock produces the tightest envelope and is appropriate for a yard or a turning head. A higher speed with partial lock is appropriate for a through movement on a street, and produces a wider path. An officer who cannot see which was used has no way to check the drawing, and will ask.

The model also assumes a competent driver making one continuous movement. Real drivers shunt. On a tight service yard, showing a single perfect sweep where the actual manoeuvre needs two bites is a drawing that will be built and then fail in use, and the operator will be the one who raises it.

Presenting the drawings

Show entry and exit as separate tracks on separate drawings or in clearly distinguished colours, because a single combined plot is unreadable and hides the worst case. Most authorities want to see the vehicle arriving, servicing and leaving in forward gear, with any reversing manoeuvre plotted in full rather than described.

Each drawing should carry the vehicle name and its dimensions, the steering lock and speed assumed, the clearance margin applied, and the source of the vehicle data. Where the vehicle came from the authority's own standard, say so in the title block.

Add the swept envelope for the check vehicles as a separate sheet, with a note explaining the frequency of the movement and how it is accommodated.

Illustrative example, for method only. A cul-de-sac of fourteen houses is served by a 26 tonne rigid refuse vehicle specified in the authority's design guide. Tracking shows the vehicle can enter, use the turning head and leave in forward gear with a 0.5 metre clearance, provided the turning head is kept free of parking, which is secured by a marked hammerhead and a condition. A pantechnicon cannot use the turning head, so a separate sheet shows it reversing 11 metres from the head to the first plot, within the authority's reversing limit. The layout is accepted without widening the street.

Where tracking supports a larger scheme, it sits inside a Transport Assessment, with the geometry of private drives and shared surfaces covered in our notes on private drive geometry and what highway officers want from shared surfaces. Construction-stage movements are a separate exercise again, and are set out in a Construction Traffic Management Plan.

PlanScope drafts those documents from your site details, and marks the vehicle and survey inputs it cannot verify so they come from the authority rather than from a default.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.