Walkthrough: drive through unit at a trunk road junction

A drive through planning application highways case at a trunk road junction stands or falls on two questions. Whether National Highways is satisfied that queueing traffic will never reach the strategic road network, and whether the odour and noise evidence holds up against the nearest dwellings. Everything else in the submission is ordinary. This walkthrough follows an illustrative scheme, a single drive through unit of 220 m² on the corner of a roadside plot, accessed from a local distributor road 90 metres from a signalised junction with an A road managed by National Highways. The figures and the sequence are illustrative rather than taken from a decided application.

The site and the junction

The plot is part of a larger commercial site with an existing access off the local road. The A road sits east of the site, and the signalised junction between the two is the constraint. Any queue that forms on the exit from the drive through lane can in principle propagate back through the site access, onto the local road and into the junction approach.

Start by establishing who controls what. The local highway authority controls the local distributor road and the site access. National Highways controls the A road and the junction where it is a trunk road. Confirm the classification from the highway authority's records rather than from a map colour, because a road that looks like a trunk road may be detrunked and vice versa.

Then work out the existing use of the plot. Where the land has an extant commercial permission, the traffic case is about the difference between the consented position and the proposal rather than about the whole trip generation. That framing is worth establishing on paper before any modelling starts.

When National Highways becomes a consultee

National Highways is a statutory consultee for development likely to affect the strategic road network. Its policy position is set out in the Department for Transport circular on the strategic road network and the delivery of sustainable development, which expects development to be located and designed so that the network continues to operate safely, and expects mitigation to be proportionate and deliverable.

Two powers matter on the programme. National Highways can ask the authority to hold the application while it considers the proposal, and it can direct that permission be refused or that particular conditions be imposed. A holding direction does not end the application, but it stops the clock in practice and can run for months. Assume that any scheme within a few hundred metres of a trunk road junction will attract one unless the transport evidence anticipates the questions.

What satisfies the consultee is rarely a more optimistic model. It is usually a design where the queue physically cannot reach the network, plus a monitoring and management commitment secured by condition.

Queue length and internal circulation

The Transport Assessment has to do three things. Establish the arrival profile at the peak, which for this use is often the Saturday lunchtime and the weekday evening rather than the classic weekday morning peak. Show the stacking capacity of the lane from the order point to the collection window, measured in vehicle lengths on the drawing. And demonstrate the behaviour when the lane fills, which is where most schemes fail.

Use observed data from comparable operating units and say where it came from. A queue prediction derived from trip rates alone will be challenged, and rightly, because the service time at the window rather than the arrival rate is what determines the queue. Where the operator holds survey data from similar units, put it in an appendix with the dates, the locations described generically and the counting method.

Internal circulation then needs to answer the awkward questions. Can a car that has joined the lane leave it without reversing? Does the lane cross the pedestrian route from the car park to the entrance, and if so, where is the priority? Can a refuse vehicle and a delivery vehicle both turn without entering the drive through lane? Draw the swept paths rather than asserting that it works.

The design response that usually satisfies the consultee is an internal reservoir. Extend the lane, or provide a bypass so that the tail of the queue sits inside the site boundary with a physical barrier between it and the access. If the geometry cannot deliver that, the honest answer is that the plot is too small for the use.

Odour and the extract design

A drive through kitchen produces frying and grilling odour continuously through the trading day. The Ventilation and Extraction Statement should set out the kitchen equipment schedule, the extract volume, the duct route, the termination height and the abatement.

Follow a recognised risk-based method. Assess the odour risk from the cooking type and the separation distance to sensitive receptors, then select abatement to match that risk, typically a grease filter stage followed by carbon or an electrostatic stage where the risk is higher. Terminate at roof level above the eaves, at least a metre above any opening within a reasonable distance, with a discharge velocity high enough to disperse rather than to fall back onto the roof.

Then say what happens when the filters are not changed. Councils condition maintenance because abatement that is not maintained does nothing, and offering a maintenance and records commitment up front is better than negotiating one after an objection.

Noise from the order point and the speaker

Two sources, two different problems. Plant noise from the extract fan, the refrigeration and the condensers is steady and is assessed under BS 4142:2014+A1:2019 against the background sound level at the nearest dwelling. Order point noise is speech, amplified, intermittent and intelligible, which is exactly the character that attracts an acoustic feature correction and exactly the character that generates complaints.

A Noise Impact Assessment for this use should model both, separately and combined, for the daytime and night-time periods the operator wants. Where late opening is proposed, expect the order point to be the binding constraint. Mitigation that works includes automatic volume control that adjusts the speaker level to ambient conditions, directional speakers, a solid screen behind the order point, and relocating the order point to the far side of the building from the dwellings.

Customer noise is the third source and the hardest to condition. Car doors, engines and conversation in the car park after midnight are the usual subject of objections from a nearby street, and the realistic answer is an hours restriction rather than a technical fix.

Lighting and signage

Forecourt and lane lighting has to be bright enough for safety and contained enough for amenity. Assess it against the obtrusive light limits for the relevant environmental zone, using the Institution of Lighting Professionals guidance, and provide an isolux plot showing vertical illuminance at the nearest residential windows. A Lighting Assessment with a curfew regime, where the lane and car park drop to a reduced level after closing, deals with most objections.

Signage is a separate consent. Illuminated signs, totems and menu boards need advertisement consent under the Town and Country Planning (Control of Advertisements) (England) Regulations 2007, and near a trunk road junction the highway authority will comment on driver distraction and on anything that could be confused with traffic signage. Apply for the advertisement consent alongside the planning application rather than after it.

The submitted pack

The application for this illustrative scheme contained a Planning Statement, a Design and Access Statement, the drawing set including a swept path and stacking plan, a Transport Assessment with a queue assessment appendix, a Travel Plan, a Ventilation and Extraction Statement, a Noise Impact Assessment, a Lighting Assessment, a drainage strategy for the additional hardstanding, a preliminary ecological appraisal for the boundary hedgerow, a litter and waste management plan, and a separate advertisement consent application.

Most drive through units are treated as sui generis rather than falling within Class E, because hot food sold for consumption off the premises sits outside that class. Confirm the use description with the case officer at pre-application, because the description on the decision notice determines what the operator can lawfully do later. A parallel sequence for a smaller commercial conversion is set out in our walkthrough of a shop becoming a children's nursery.

Conditions to expect

Expect conditions on opening hours, delivery and servicing hours, the order point speaker system and its volume control, extract abatement and its maintenance records, a lighting curfew, litter patrols within a stated radius, retention of the stacking capacity shown on the approved plan, a car park management plan, and implementation of the travel plan with monitoring. Some authorities add a marshalling condition triggered by observed queueing, which is worth negotiating carefully because it can be expensive to operate.

Read the stacking condition especially closely. A condition that requires the lane to be retained as shown will prevent the operator reconfiguring the layout later without a further application.

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. For specialist technical reports, qualified professional input may be required.

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