Which design vehicles to test in a swept path analysis
A tracking drawing is only as good as the vehicle chosen. The routine and occasional movements to test, and the parked car case most submissions omit.
A swept path analysis is only as good as the vehicle you chose to test. Pick the governing vehicle wrongly and the drawing proves nothing: a layout that works for a transit van and fails for an 11.6 metre refuse vehicle will be approved and then become somebody's problem on the first collection day.
The governing vehicle is the largest vehicle that will need to use the layout as part of its normal operation. Not the largest vehicle imaginable, and not the one that is convenient to draw.
Choosing the governing vehicle
Work through the vehicles the development will actually attract, and separate routine movements from occasional ones.
For a residential scheme that normally means the refuse collection vehicle, a removal lorry, a delivery van and a fire appliance. For a commercial or industrial unit it means the largest articulated vehicle the occupier expects, plus rigid deliveries and a refuse vehicle. For a food store it means an articulated vehicle at the service yard and smaller vehicles elsewhere. For a school it means a coach, a refuse vehicle and a kitchen delivery.
Routine movements have to be accommodated in full, with clearance. Occasional movements can be accommodated with overrun areas, a managed arrangement or a longer reversing distance, provided the drawing says so and the management is secured.
Ask the local authority waste team for the dimensions and the turning requirements of their own refuse fleet. Authorities operate different vehicles, several require that a collection vehicle does not reverse more than a stated distance, and some will not collect from a private road at all. That single enquiry changes more layouts than any other.
Where a scheme needs a Transport Assessment, list the design vehicles and the reason each was selected in the report. A reviewer who cannot see why a vehicle was chosen will assume it was chosen because it fitted.
Sources for vehicle dimensions
Use published dimensions, cite them, and do not take them from the software's default library without checking.
| Source | What it gives |
|---|---|
| Road Vehicles (Construction and Use) Regulations 1986 | Maximum legal dimensions and weights for vehicles on the road |
| Manual for Streets and its companion guidance | Design vehicles and geometry for residential and lightly trafficked streets |
| Design Manual for Roads and Bridges | Design vehicles and junction geometry for the trunk and principal road network |
| The local waste collection authority | The actual refuse vehicle in service, with its turning circle |
| The local fire and rescue service | The relevant appliance type for the area |
| The occupier or operator | The articulated or rigid vehicles a specific tenant will use |
Record the length, width, wheelbase, overhangs, turning circle and the body swept envelope for each vehicle used, in a legend on the drawing. A tracking drawing with an unnamed vehicle is not evidence.
One point on the legal maximum. A 16.5 metre articulated vehicle is the common standard for a general goods delivery, but drawbar and longer semi-trailer combinations exist and some operators use them. If the occupier is known, ask. If not, say which vehicle has been assumed and that the layout should be tested again if the operator's fleet differs.
Testing entry, exit and conflict cases
Draw the manoeuvres that happen, not the one that works.
- Entry from the public highway from both directions of approach, including the right turn in across opposing traffic where that is permitted.
- Travel through the site to each destination, with every pinch point shown.
- Arrival at the service bay, loading area or bin collection point in the orientation required for the operation.
- Departure, in forward gear where possible, with any reversing distance measured and stated.
- Two vehicles passing, where the layout is two way and a refuse vehicle may meet a car.
- The same manoeuvres with all marked parking bays occupied, which is the test most often omitted and the one that matters.
- Conflict with pedestrian and cycle routes, showing where the swept envelope crosses a footway or a crossing point.
The parked car case deserves its own paragraph. A tracking drawing produced on an empty site plan is a statement about geometry. A tracking drawing with every bay occupied is a statement about whether the layout works, and a highway officer who has seen a few schemes will ask for it.
Overrun areas and kerb treatment
Where the swept envelope crosses a kerb line, you have two honest options: design the surface to be driven over, or move the kerb.
An overrun area has to be built for it. That means a flush or chamfered kerb, a construction designed for the wheel load of the governing vehicle, and a surface treatment that reads as part of the carriageway rather than as a footway. Setts, reinforced grass and heavy duty block paving are all used. What does not work is a standard footway construction with a 125mm upstand, because vehicles will mount it and it will fail.
Distinguish the wheel path from the body swept envelope on the drawing. The wheel path determines the construction. The body envelope, which extends further on the outside of a turn, determines clearance to walls, columns, street furniture, signs and planting. Many layouts pass on wheel path and fail on body overhang against a corner of a building.
Allow clearance rather than drawing to the kerb face. A nominal allowance to kerbs and a larger one to walls and fixed structures is normal practice; state the figure used.
Gradient and crossfall effects
Swept path software works in two dimensions. Real vehicles operate in three.
Three effects to check by hand:
Grounding at a change of gradient. A long wheelbase articulated vehicle entering a ramp, or crossing a hump at the site entrance, can ground on the transition. Check the ramp transition length and the vehicle's ground clearance.
Loss of traction and control on a slope. Refuse vehicles and fire appliances both have practical gradient limits, and some waste authorities will not collect from a gradient above a stated figure.
Crossfall at a turning area. A cambered turning head designed for drainage can cause a loaded vehicle to lean, and where the turn is tight against a wall the body overhang swings lower than the drawing suggests.
Where the layout depends on levels, give the gradients on the tracking drawing. Where a service yard has a ramp, draw a long section through it.
Drawing conventions reviewers expect
Highway officers read dozens of these, and a drawing that follows the convention gets a quicker answer.
Put the vehicle name and full dimensions in a key. State the software and version, and the speed assumption used for the simulation. Show wheel paths and body envelope in different line types, with a legend. Draw at a scale where the clearances can be measured, usually 1:200 for a site layout and 1:500 only for an overview. Give one manoeuvre per drawing, or a clearly separated set, rather than overlaying six paths in different colours on one sheet. Annotate the critical clearance dimensions rather than leaving them to be scaled. And show the parked car case as a separate drawing.
Where a bin collection point is involved, the collection vehicle's position and the drag distance from the store to the vehicle both need showing, and the arrangement has to match the Waste Management Strategy. The detail of how those points are positioned in a flatted scheme is set out in bin storage and collection points in flatted schemes.
Where the analysis changes the layout
Tracking is a design tool, not a validation exercise, and it costs least when it is run early.
The changes it produces are predictable. Corner radii increase, which takes land from the plot at the junction. Turning heads grow, which usually costs a parking space or two. Bin stores move closer to the adoptable road, which affects the ground floor plan. Parking bays near a corner are removed to give a refuse vehicle room to turn. A service yard gains a metre of depth, which pushes the building line back. Occasionally the access point moves entirely.
Every one of those changes is easy at concept stage and expensive after a permission. Run the governing vehicle through the first sketch layout, not the planning drawings, and run it again after the landscape proposals arrive. Where construction vehicles are the issue rather than operational ones, the same geometry work belongs in the Construction Traffic Management Plan, drawn for the largest vehicle the build will need.
Enter your postcode on PlanScope to see which transport documents a scheme with constrained access is likely to need.
PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. Councils usually expect swept path analysis to be prepared by a suitably qualified transport planner or highway engineer, and professional review is strongly advised.
Frequently asked questions
How do I choose the governing vehicle?
Take the largest vehicle that will use the layout as part of normal operation, separating routine movements from occasional ones. Routine movements must be accommodated in full with clearance; occasional ones can rely on overrun areas or managed arrangements provided the drawing says so and the management is secured by condition.
Where do refuse vehicle dimensions come from?
From the local waste collection authority, because fleets differ between councils. Several authorities also limit how far a collection vehicle may reverse, and some will not collect from a private road at all. That single enquiry changes more layouts than any other piece of guidance.
Why does the parked car case matter?
Because a tracking drawing on an empty site plan only tests geometry. Once every marked bay is occupied, the available width at corners and turning heads often falls below what the governing vehicle needs. Highway officers increasingly ask for the occupied case as a separate drawing.
What is the difference between wheel path and body envelope?
The wheel path is where the tyres run and it determines the construction and kerb treatment. The body swept envelope extends further on the outside of a turn and determines clearance to walls, columns, signs and planting. Many layouts pass on wheel path and fail on body overhang at a building corner.
Does gradient affect a swept path analysis?
Yes, though the software works in two dimensions. Check grounding at gradient transitions for long wheelbase vehicles, practical gradient limits for refuse vehicles and fire appliances, and the effect of crossfall at a tight turning head where a leaning body swings lower than the plan suggests.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.