Appendices that complete a Transport Assessment
Highway engineers read the appendices first. Here is what each appendix of a Transport Assessment has to contain so the capacity results can be audited rather than argued about.
A Transport Assessment is judged on its appendices as much as its chapters, because that is where the highway authority's engineer goes first. The body sets out the argument. The appendices prove it, and an engineer who cannot reproduce your junction results from the material supplied will either ask for the files or recommend a holding objection. Budget time for the appendix set rather than treating it as the thing you staple on at four o'clock on submission day.
The practical rule is simple. Anything a reader needs to follow the argument goes in the body. Anything a reviewer needs to test the argument goes behind it.
What belongs in the body and what belongs behind it
Keep the body to the development description, the policy context, the baseline conditions, trip generation, distribution, assignment, the capacity results as summary tables, access and parking, sustainable travel measures and the residual effects. Summary tables with the headline capacity figures belong in the chapters. Full model output, raw survey sheets and database extracts do not.
The test is whether a chapter still reads cleanly when printed. A section interrupted by eight pages of turning counts has lost its reader, and the officer writing the committee report will take their conclusions from whichever paragraph they can find. Our note on the content of a Transport Assessment covers the chapter structure itself.
Appendices are referenced, not dumped. Every appendix should be cited from at least one place in the body. If nothing in the body points at it, ask why it is there.
Survey data and the raw counts
The survey appendix is the one most often incomplete. It needs the counts themselves, the method, and enough context for someone to judge whether the data represents a normal week.
Include for each survey:
- the date, day of week, start and finish times, and the weather
- the location, with a plan showing count points and movement numbering
- the classification used, and whether pedestrians and cycles were counted
- for automatic counts, the full period rather than a selected day
- any adjustment applied, with the reason stated
Surveys should be carried out in neutral conditions. School holidays, the weeks around Christmas and the main summer holiday period distort flows, so counts from those weeks need either a justification or a correction factor with a stated source. Where the scheme turns on parking, the beat survey sheets and the stress calculation go in their own appendix, and the method behind a Parking Survey should be stated rather than assumed.
Where a highway authority specified survey dates in pre-application correspondence, put that correspondence in the pack. It saves an argument about whether the data is current.
Junction modelling outputs and audit files
Highway authorities audit models. Supply the summary tables, the inputs that generated them, and the electronic model files on request. A reviewer wants to see geometry inputs, flows, and results for each assessment year and peak, with the base year validated against observed queues.
| Appendix content | What the reviewer checks |
|---|---|
| Geometry inputs for each arm | Lane widths, flare lengths, radii match the drawing |
| Demand flows by movement | Agreement with the survey appendix and with growth factors |
| Base year results against observed queues | Whether the model reflects reality before it predicts |
| Future year results with and without development | The actual effect of the proposal |
| Sensitivity tests | How close the junction is to the point of failure |
State the growth method and the source dataset for traffic growth, the assessment years, and every committed development added to the base. Where a junction already operates over capacity, say so in the body and let the appendix show by how much. Hiding it in a table of ratios does not work, because the engineer reads ratios for a living.
One detail that causes avoidable delay: give model files meaningful names that match the appendix numbering. A folder of files named after the software default tells the reviewer nothing.
Trip rate database extracts
Trip rates taken from the TRICS database have to be reproducible. The appendix needs the full output report, not a single rate lifted into the body.
Record the land use category selected, the geographical and date filters applied, the days of week included, the population and parking filters, the number of surveys in the final set, and the list of sites with their sizes. Where sites were excluded by hand, say which and why. A reviewer who runs the same query and gets a different answer will not accept the trip generation chapter.
Multi-modal rates deserve the same treatment. Where a scheme relies on a low car-driver rate because of its location, the comparison sites have to be comparable on public transport accessibility, and the appendix should let that be checked. The Travel Plan then has to deliver the mode shift the rates assume, which is the point at which optimistic trip generation becomes a planning condition you cannot meet.
Where trip rates were agreed with the highway authority in scoping, cite the agreement.
Swept path and visibility drawings
These are drawings, so they belong on sheets with titles, scales, revision numbers and north points.
The usual set covers the largest service vehicle expected, the refuse vehicle to the local authority's specified dimensions, a fire appliance where access standards apply, and any articulated delivery vehicle for commercial schemes. Show entry and exit in both directions, and show the conflict case where two vehicles meet. Where the refuse vehicle cannot reach the bin store, the collection point moves, which is why the swept path drawings and the waste storage calculations need to be prepared together rather than by two people who never speak.
Visibility appendices should state the design speed, the measured or recorded speeds supporting it, the standard applied, and the eye and object heights used. Include forward visibility on bends, pedestrian intervisibility splays at the access, and any splay that falls across third-party land, because a splay you do not control is not a splay.
Correspondence with the highway authority
A correspondence appendix is the least costly insurance in the document. Include the scoping request and the response, agreed survey dates, agreed assessment years and growth assumptions, agreed junctions for assessment, and any agreement on trip rates or mitigation.
Reproduce the exchange rather than summarising it. A summary invites a reply that the authority remembers the conversation differently. Where an officer declined to comment at scoping, say that too, with the date.
Pre-application notes on access and inclusive design also sit well here, and they connect to the wider access material described in our note on access and inclusion evidence.
Numbering and indexing an appendix set
Letter the appendices and number the sheets within them. A contents page at the front of the appendix volume, matching the references in the body exactly, removes most of the friction in a review.
Practical points that matter more than they should:
- Bookmark the PDF, one bookmark per appendix, with sub-bookmarks for model runs.
- Check the authority's file size limit before submission and split the volume if needed, keeping appendices whole rather than cutting mid-document.
- Keep the revision suffix on every drawing, and make sure the appendix index lists the same revision that the body cites.
- Supply a separate electronic model file package where the authority asks for one, listed in the index so its absence is obvious if it goes astray.
- Reissue the whole volume, not a loose sheet, when anything changes.
An appendix set assembled this way does something useful beyond compliance. It makes the assessment auditable, which is the only reason a highway authority ever accepts a capacity conclusion it did not calculate itself.
Browse all 66 PlanScope report types and start a draft of the assessment chapters while your surveys are still in the field. 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, and councils expect a Transport Assessment to carry a suitably qualified author.
Frequently asked questions
What goes in a Transport Assessment appendix rather than the main text?
Raw survey sheets, full junction model inputs and outputs, trip rate database reports, swept path and visibility drawings, and correspondence with the highway authority. The chapters carry the argument and summary results. Anything a reviewer needs to reproduce a number belongs behind the report, cross-referenced from the paragraph that uses it.
Does a highway authority need the electronic model files?
Many authorities audit junction models and will ask for the files so results can be rebuilt. Supply them in a clearly named package listed in the appendix index. Name the files to match the appendix numbering rather than leaving software defaults, because an auditor who cannot tell which run is which will ask again and lose a week.
How much detail does a TRICS extract need?
The full output report, including the land use category, geographical and date filters, days of week, population and parking filters, the number of surveys retained and the site list. If any site was excluded by hand, state which and why. A reviewer who repeats the query should reach the same rate you used in the trip generation chapter.
When are traffic counts too old or unrepresentative?
Counts taken during school holidays, the weeks around Christmas or the main summer holiday are usually treated as unrepresentative without a correction factor and a stated source. Age depends on how much has changed locally, so agree acceptable survey dates with the highway authority at scoping and keep that correspondence in the appendix.
Do visibility splays across land I do not own count?
Not reliably. A splay depends on keeping the area clear in perpetuity, which needs either ownership, a highway verge, or an agreement you can demonstrate. Show the land ownership on the visibility drawing. If the splay crosses a third party's garden or hedge, expect the highway authority to treat it as undeliverable.
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.