Transport Statement or Transport Assessment: which one
The difference between the two documents is depth, not subject matter. Here is how the thresholds work, what scoping with the highway authority should settle, and where budgets go wrong.
The choice between a transport statement and a transport assessment is a choice about depth, and it is made by the highway authority rather than by you. A Transport Statement is a short document for a development with modest transport effects: it describes the site, the access, the local walking, cycling and public transport offer, and gives a light trip generation estimate. A Transport Assessment does the same things and then models the effect on the network, tests junction capacity, examines accident records and assesses the residual impacts against policy. On a 60-dwelling scheme the second will cost several times the first, so the wrong assumption at budget stage is expensive.
Two things decide which you need. Scale, and the sensitivity of the network you are joining.
What each document is for
A Transport Statement answers the question: does this development cause any transport problem worth investigating. It sets out existing conditions, the proposed access arrangement, parking provision against the local standard, servicing and refuse access, and a trip estimate. Where the answer is no, and the highway authority accepts that, the statement is the end of the matter.
A Transport Assessment answers a harder question: what are the effects on specified junctions and links in specified assessment years, and are the residual cumulative impacts on the network severe. That requires agreed traffic counts, an agreed trip rate methodology, distribution and assignment of trips onto the network, junction capacity modelling, and an assessment of accessibility by non-car modes. The evidence base has to be defensible because the highway authority's consultation response, and sometimes a highways objection at committee, will turn on it.
| Element | Transport Statement | Transport Assessment |
|---|---|---|
| Existing conditions and access | Yes | Yes, with surveyed counts |
| Trip generation | Indicative estimate | Agreed TRICS methodology |
| Junction capacity modelling | No | Yes, agreed junctions and years |
| Accident analysis | Brief | Formal review of recorded collisions |
| Non-car accessibility | Described | Assessed against policy |
| Travel plan | Sometimes a framework | Usually a full plan |
The thresholds that separate them
There is no single national numeric threshold. Planning Practice Guidance on travel plans, transport assessments and statements sets the principle that the scale of the evidence should be proportionate to the scale and location of the development, and leaves the trigger points to local policy and to the highway authority. Many authorities publish indicative thresholds in a local validation checklist or a parking and transport supplementary planning document.
The thresholds PlanScope uses to flag a Transport Assessment are 50 or more dwellings or 2,500 m² or more of floorspace, with a Transport Statement flagged below that. Those figures reflect common local practice, and they are a useful starting point for budgeting. They are not a rule. The authority's own validation list and national policy take precedence, and location can override scale in both directions: 25 dwellings on a rural single-track lane with a substandard junction may need a full assessment, while 60 flats above a city centre station may not.
Three location factors commonly push a scheme up a tier.
- Access onto or close to the strategic road network, which brings National Highways in as a statutory consultee with its own expectations.
- A location inside an Air Quality Management Area, where traffic changes feed an air quality assessment.
- A site where the existing junction already operates near capacity, so any increment has to be modelled.
Scoping with the highway authority before you commission
The single most useful hour on any transport evidence base is a scoping conversation with the highway authority's development management team, ideally through pre-application advice so the response is recorded. What that conversation should settle:
- Which document is required, and whether a travel plan is expected alongside.
- Which junctions are to be assessed, and in which assessment years.
- Whether existing traffic counts are acceptable or new surveys are needed, and in which neutral months.
- The trip rate methodology and the site selection criteria for it.
- Committed development to be included in the background growth.
- Parking standards to be applied, including cycle parking and electric vehicle charging.
Get that in writing. A scope agreed in an email protects the budget and removes the most common cause of a consultation response asking for further work: the consultant modelled the wrong junction, or used the wrong year, or excluded a committed scheme the authority expects to see.
Trip generation and the TRICS database
Trip rates in the United Kingdom are conventionally derived from TRICS, the industry survey database. The method is straightforward in principle: select surveys of comparable developments, filter by land use, location type, parking provision and settlement size, then apply the resulting rates per unit or per 100 m² to the proposal. The judgement lies in the filtering, and that is where an authority will challenge the work.
Two disciplines make a trip generation section credible. Publish the filtering criteria and the number of surveys in the selected set, so the calculation can be reproduced. And show the existing site's trips where there is an existing lawful use, because a change of use on a site with an active retail unit may generate fewer trips than the baseline, and net impact is what matters. An illustrative example: a vacant 800 m² warehouse converted to eight flats may show a net reduction in weekday peak vehicle trips, which turns the transport case from a defensive exercise into a positive one.
Junction capacity, access design and what follows
Capacity modelling uses standard tools for priority junctions, roundabouts and signals, reported as ratio of flow to capacity, queue lengths and delay. The convention is to report the base year, the opening year and a future assessment year with background growth, in both peak periods. Access design is assessed against visibility standards and the relevant design guidance, with Manual for Streets applying to residential streets and the design manual for roads and bridges applying on the strategic network.
Where mitigation is needed, it usually arrives as a highway works package under section 278 of the Highways Act 1980, secured by condition or agreement. Budget for the design fees, the technical approval process and the commuted sums, which are frequently missed at appraisal stage.
Travel plans, parking evidence and construction traffic
A Transport Assessment normally comes with a Travel Plan setting mode share targets, measures and monitoring. For residential majors of 150 or more dwellings, Active Travel England is a statutory consultee and will comment on walking and cycling provision, so the active travel content needs to be substantive rather than a paragraph.
Parking is a separate evidence question. Where the proposal relies on existing on-street capacity, a Parking Survey gives the authority something to test rather than an assertion. And for any scheme with a meaningful construction phase, a Construction Traffic Management Plan is usually required by condition, covering routing, wheel washing, delivery hours and site access.
If you are still working out which of the two transport documents the site needs, and what else the application will carry, the Transport Assessment page sets out the scope and the typical author, and the wider report index shows the rest of the pack. Councils expect a suitably qualified transport planner for assessment level work, and professional review is strongly advised.
PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it.
Frequently asked questions
When is a Transport Statement enough?
Where the development's transport effects are modest and the local highway authority accepts that no modelling is needed. That commonly means smaller residential and commercial schemes in accessible locations with an existing suitable access. The authority decides, so confirm it through pre-application advice or the validation checklist rather than assuming from unit numbers alone.
What is the threshold for a Transport Assessment?
There is no single national figure. Planning Practice Guidance requires evidence proportionate to the scale and location of the development and leaves trigger points to local policy. Indicative local thresholds around 50 dwellings or 2,500 m² of floorspace are common, but a sensitive rural access can pull a much smaller scheme into full assessment.
What is TRICS used for?
TRICS is the survey database from which vehicle, person and multi-modal trip rates are derived for a proposed land use. Consultants select comparable surveys, filter by land use, location and parking provision, then apply the rates to the development. Publish the filter criteria and the number of surveys so the highway authority can reproduce the calculation.
Do I need both a Transport Assessment and a Travel Plan?
Usually yes on major schemes. The assessment quantifies effects; the travel plan sets out how non-car travel will be promoted, with targets, measures, a coordinator and monitoring. Smaller schemes often provide a travel plan framework instead, with the full plan secured by condition before occupation.
Can an existing use reduce the assessed impact?
Yes. Where the site has a lawful existing use, its trips form the baseline and only the net change is assessed. Evidence the existing use properly, with survey data where the premises are occupied or comparable TRICS rates where they are vacant, and set out the assumption clearly so the authority can check it.
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.