Transport Assessments

What Is a Transport Assessment — And When Do You Need One?

If you are applying for planning permission for a new development — whether that is housing, a commercial unit, a warehouse, or even a school — there is a good chance your local planning authority will ask for a Transport Assessment or a Transport Statement before they will consider your application.

For many people, this comes as a surprise. What does transport have to do with planning permission? And why does it sometimes hold up an application for months?

This guide explains what a Transport Assessment is, how it differs from a Transport Statement, when you are likely to need one, and what the most common mistakes are that cause applications to stall.

What is a Transport Assessment?

A Transport Assessment (often shortened to TA) is a technical document submitted alongside a planning application. Its job is to analyse how a proposed development will affect the transport network around it — covering roads, junctions, footpaths, cycle routes, and public transport links.

In practical terms, it answers the question: if this development is built, what happens to the way people and vehicles move in and around this area?

A well-prepared Transport Assessment does not just identify potential problems. It also sets out what measures the developer will put in place to manage those impacts — things like new pedestrian crossings, improved cycle access, contributions to local bus services, or changes to junction layouts.

The requirement for a Transport Assessment is set out in the National Planning Policy Framework (NPPF), which states that developments likely to generate significant amounts of movement should be supported by a transport statement or transport assessment.

Transport Assessment or Transport Statement — what is the difference?

These two documents are often confused, but they serve different purposes depending on the scale of a development.

A Transport Statement (TS) is the lighter version. It is used for smaller developments where the impact on the transport network is expected to be limited. It covers the basics — site access, walking and cycling routes, and nearby public transport — without the full technical depth of a Transport Assessment.

A Transport Assessment (TA) is the full version. It is required for larger or more complex developments where the impact on the surrounding transport network is significant. It includes detailed traffic modelling, junction analysis, and a thorough look at all modes of travel to and from the site.

As a rough guide used by many local authorities, a TA is typically expected when a development generates more than around 50 vehicle trips during peak hours. For housing, this often equates to developments of around 80 or more homes. For food retail, it tends to be around 800 square metres of floor space. These are not fixed rules — they vary by location and by the sensitivity of the local road network — but they give a useful starting point.

When is a Transport Assessment required?

This is where things get less straightforward. Since 2014, there have been no fixed national thresholds written into planning policy. Whether you need a TA, a TS, or neither is a matter of judgment for your local planning authority — based on the type, scale, and location of your development.

However, a Transport Assessment is more likely to be required in the following situations:

A large housing development, typically 80 or more homes, though some authorities set their own thresholds.

A new commercial, retail or industrial development that will generate significant vehicle movements during peak hours.

Any development close to roads or junctions that are already at or near capacity.

Development in a location where public transport, cycling or walking infrastructure is limited.

Any scheme not in line with the adopted Local Plan, where transport impacts need careful scrutiny.

A development that includes 100 or more parking spaces.

Even for smaller developments that fall below these levels, your local planning authority may still request a Transport Statement if the site is in a sensitive location — near a school, a busy town centre junction, or an area with known congestion issues.

The clearest advice here is this: do not wait to be asked. Speak to your local highway authority or a transport planning consultant before you submit your application. Finding out what is required early saves significant time and cost later.

What goes inside a Transport Assessment?

The exact contents will vary depending on the development and what the local authority asks for. However, a typical Transport Assessment will cover:

A description of the proposed development and its likely users.

An assessment of the existing transport network around the site — roads, junctions, footpaths, cycle routes, and public transport.

Trip generation figures — an estimate of how many additional vehicle and person trips the development will create, and when.

A junction analysis — technical modelling of how nearby junctions will perform once the development is occupied, usually at morning and evening peak times.

An access strategy — how vehicles, pedestrians, cyclists, and public transport users will enter and leave the site.

Mitigation measures — what the developer proposes to do to manage any negative impacts on the transport network.

A sustainable transport section — in line with the updated NPPF, this should now address the vision for how people will travel to and from the site, not just predict car movements.

Many Transport Assessments are also accompanied by a Travel Plan, which is a separate document setting out ongoing measures to encourage sustainable travel once the development is occupied — things like cycle storage, shower facilities, and discounted bus passes.

How has the NPPF 2024 changed things?

The December 2024 update to the NPPF has shifted the way Transport Assessments are expected to be approached.

Previously, the dominant model was to predict how many cars a development would generate and then demonstrate that the road network could cope. This is known as predict and provide.

The updated NPPF moves away from this. It now encourages what is called a vision-led approach — starting with a clear vision for how the development should function in transport terms, and then demonstrating how that vision will be achieved. The emphasis is on sustainable travel, modal shift, and creating places that work for people on foot, on bikes, and on public transport — not just for drivers.

In practice, this means Transport Assessments that still rely heavily on worst-case car traffic projections may no longer satisfy planning officers. Local authorities are being encouraged to accept some increase in traffic if a development genuinely improves sustainable transport options and supports the kind of place the community wants.

This is a significant change. If you or your consultants are using an approach to transport assessment that was standard five years ago, it may now be out of step with current policy expectations.

What happens if you do not submit one?

If a Transport Assessment or Transport Statement is required and you do not provide one, your planning application is likely to be declared invalid and will not be registered by the local planning authority. In other words, it will not even be considered.

If you submit one that is inadequate — for example, one that uses outdated methods, fails to test realistic scenarios, or does not address sustainable travel — your application may be refused on transport grounds, or you may be asked to provide additional information, which delays the process and adds cost.

Getting the transport assessment right from the start is almost always quicker and cheaper than having to revise it under pressure during the determination period.

The most common pitfalls

Leaving it too late. Transport Assessments take time to prepare — traffic surveys, junction modelling, and consultation with the highway authority all need to happen before you can finalise the document. Starting the process only after you have submitted your application or been asked for one by the planning officer puts you at an immediate disadvantage.

Not agreeing on the scope in advance. Before preparing a TA, it is standard practice to agree a scoping document with the local highway authority — a formal agreement on what the assessment needs to cover. Skipping this step often results in having to redo significant amounts of work.

Using a template rather than a tailored assessment. Every site is different. A TA that applies a generic approach without properly engaging with the specific characteristics of the local transport network is unlikely to satisfy planning officers.

Ignoring sustainable travel. Under the updated NPPF, a TA that focuses almost entirely on car trips and junction capacity is increasingly seen as out of date. Assessments now need to demonstrate how walking, cycling, and public transport have been genuinely designed into the scheme.

Underestimating local sensitivity. A development that would attract little transport scrutiny in one location may face significant challenges in another — particularly in areas with known congestion problems, limited road capacity, or poor public transport.

A quick summary

A Transport Assessment is a technical planning document that analyses how a proposed development will affect transport in the surrounding area.

A Transport Statement is a lighter version, used for smaller developments with limited transport impacts.

There are no fixed national thresholds — your local planning authority decides what is required based on the scale and location of your development.

Under the updated NPPF, Transport Assessments are expected to take a vision-led approach, with a genuine focus on sustainable travel.

Getting this right early — through pre-application discussions with the highway authority and good professional advice — is the most reliable way to avoid delays.

Conclusion

If you are in the early stages of planning a development and are not sure whether you need a Transport Assessment, the safest starting point is a pre-application discussion with your local planning authority. They can advise on what will be required before you commit to a full application.

This post is intended as a general guide to planning policy. For advice specific to your project or site, always consult a qualified transport planner.