Swept path analysis and what it proves

Swept path analysis is a scaled tracking drawing that traces the wheel paths and swept body envelope of a chosen design vehicle as it enters a site, turns within it and leaves. It proves one narrow thing, and it is worth being precise about which: that a vehicle of the stated dimensions can complete the stated movement on the geometry drawn, at crawl speed, within the clearances shown. It does not prove the access is safe. It does not show that visibility splays work, that the refuse crew will agree to come in, or that the highway authority will adopt the road.

Most highway objections that mention tracking are not really about the software. They are about the vehicle someone chose, the clearance they allowed, or a movement nobody bothered to draw.

What the drawing actually demonstrates

The software steers a defined vehicle model along a path you set, then plots the envelope swept by every part of the body, including front and rear overhang, at a given steering lock. What comes back is geometry, not behaviour. A tracking plot that shows a 11.6m refuse vehicle turning within a courtyard with 100mm to spare is arithmetically true and practically useless, because no driver reverses off a public road into a bin store with 100mm of margin on a wet morning.

So read the output as a test of whether the movement is possible, then apply judgement about whether it is reasonable. Highway officers do exactly that. They look at the tightest point on the plot, ask what happens if the driver is 300mm off line, and ask what the consequence is when the answer is a bollard, a rendered wall or a parked car.

The drawing also carries an implicit claim about the route. If your plot starts at the site boundary, you have said nothing about whether the vehicle can reach the boundary at all. Narrow rural lanes, a pinch point at a bridge, or an existing on-street parking regime can defeat a perfectly good on-site layout.

Choosing the design vehicle

The design vehicle is the largest vehicle that will regularly use the access, not the largest that could conceivably arrive. Getting this wrong in either direction costs time. Choose too small and the officer asks for a re-run. Choose an articulated vehicle for a five-house cul-de-sac and you will be designing radii the scheme does not need, eating frontage and losing planting.

Sensible practice is to state the choice and the reasoning on the drawing itself. A short note reading "design vehicle: 11.6m rigid refuse vehicle, per the local authority collection fleet. Largest occasional vehicle 10m removal lorry, tracked separately at reduced clearance" tells the officer you have thought about it.

Dimensions for standard vehicle types come from the libraries built into tracking software and from highway authority design guides. Where a council publishes its own refuse vehicle dimensions, use those in preference to a generic model, and say so.

Refuse, delivery and emergency access

Three separate authorities can take an interest in the same piece of tarmac, and they do not want the same things.

The waste service cares about carry distance for bins, whether the crew has to reverse, and the loading height at the collection point. Many councils publish a maximum bin drag distance and a policy against reversing more than a set length. The highway authority cares about the adopted extent, radii, forward visibility and the turning head standard. The fire authority cares about access for a pumping appliance, working space and the distance from the appliance to the furthest point of the building, which is set out in Approved Document B rather than in any highway guide.

Track all three where they differ. A layout that satisfies refuse often fails the fire appliance because the appliance is wider and needs greater carriageway width on the bend, not just more radius.

Kerb clearance, overrun and gradient

Clearance is the number that gets argued about. A common expectation is a minimum of 0.5m between the swept envelope and any kerb or fixed obstruction, with more where the movement is repeated daily or where the obstruction is something that will be damaged or will damage the vehicle. Some authorities accept 0.25m in constrained retrofit situations and some ask for 1m against a boundary wall. Check the local design guide before you set the drawing up, because re-running a scheme at a different clearance can change the whole site layout.

Overrun areas are a legitimate design response and an easy way to lose credibility. If you are showing the rear wheels crossing a strip of contrasting block paving, that strip has to be built to carry the axle load, drained, and kept clear of street furniture, planting and parked cars. An overrun strip that doubles as a footway is usually refused.

Gradient rarely appears on a tracking plot and regularly causes the problem. A long-wheelbase vehicle grounding on a change of gradient at the back of footway, or a low-loader unable to pull off a steep access, will not show up in plan. Add a longitudinal section through the access with the ramp gradients and the vehicle ground clearance annotated.

Reversing distances and turning heads

Adopted standards generally cap reversing distance for service vehicles and require a turning head where a cul-de-sac exceeds a stated length. The usual forms are a hammerhead, a banjo or a full turning circle, and each has a different land take and a different effect on frontage parking. A banjo eats less frontage than a hammerhead of the same capability but is harder to keep free of parked cars.

An illustrative example. A developer proposes six houses on a 55m private drive off a classified road. The tracking shows a refuse vehicle entering, reversing 22m and leaving in forward gear. The highway authority's guide sets a 12m maximum reversing distance for refuse vehicles. The options are a hammerhead at the head of the drive, a bin collection point within 25m of the highway with an agreed drag distance, or a private collection arrangement secured by an obligation. The tracking drawing did not decide anything. It showed which of three conversations to have, and that is generally what a good one does.

Where tracking drawings fail at validation

The failures repeat. A drawing submitted without a scale bar or with the scale wrong after a PDF export. A plot of entry only, with no exit movement. Vehicles tracked to the site boundary but not through the existing access onto the public road. No annotation of the vehicle type, wheelbase or clearance used. Tracking over land the applicant does not control, which surfaces later as a red line problem rather than a highway one.

And the quiet one: tracking that contradicts the architectural layout, because the transport consultant worked from an earlier plan. Date and revision both drawings and cross-check the bin store, the parking bays and the bollard positions before either goes in the pack. Where a scheme needs a full Transport Assessment, the tracking usually sits as an appendix to it. On smaller schemes it goes in as a standalone drawing alongside a Transport Statement.

Construction traffic is a separate exercise. The vehicles are larger, the routes differ and the site layout during works bears little relation to the finished scheme, so the tracking that supports a Construction Traffic Management Plan should be drawn for that phase rather than borrowed from the operational plot.

Producing a drawing the highway officer accepts

Work in this order.

1. Find the local highway authority design guide and note the required clearance, reversing distance, turning head standard and refuse vehicle dimensions.
2. Fix the design vehicle and record why you chose it.
3. Track the whole journey from the public highway to the parking or loading position and back out, not just the on-site part.
4. Run the fire appliance and the refuse vehicle separately rather than assuming one covers the other.
5. Annotate scale, vehicle model, wheelbase, steering lock, clearance and the drawing revision.
6. Section the access longitudinally where gradients change.
7. Send the result to the highway officer at pre-application stage rather than at validation.

That last step is the one people skip. A twenty minute conversation about which refuse vehicle to use can save a month of consultation and a redesign of the whole frontage.

Where parking capacity is also in dispute, tracking and a Parking Survey answer different questions and both may be needed, since a layout can track perfectly and still fail on the number of spaces provided.

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. Tracking drawings themselves are a drafting task for a transport planner or highway engineer, and PlanScope does not produce them.