Agreeing a transport assessment scoping note

A transport assessment scoping note is the least expensive document in the evidence base and the one that saves the most money. Four pages, agreed in writing with the highway authority before any survey is commissioned, fix the study area, the assessment years, the trip generation method and the survey dates. Everything after that is arithmetic.

Skip it and you will model six junctions, submit, and be told the authority wanted a seventh, in a different year, with different trip rates. That is a three-month delay and a second set of fees.

What a scoping note fixes in advance

A scoping note is not a mini assessment. It is a statement of method, and it should be short enough that a busy highway engineer reads all of it.

Cover the site and its access arrangements, the development quantum by land use, the study area and the junctions proposed for assessment, the base year and the assessment years, the committed developments to be included, the trip generation and distribution method, the survey programme, the modelling software, the collision data period, the parking approach, and the scope of the travel plan.

State the level of assessment you are proposing and why. The difference between a Transport Statement and a full Transport Assessment is proportionality, and national guidance expects the scale of the work to match the scale of the transport issues rather than the scale of the development alone.

Where the site is near the strategic road network, National Highways is a separate consultee with its own expectations, and the scoping note should go to both authorities at the same time. For residential schemes above the statutory threshold, Active Travel England is also a consultee, and its interest is in walking, wheeling and cycling provision rather than junction capacity.

Study area and the junctions to model

The study area is where most disagreements start. The principle is that junctions are assessed where development traffic makes a material difference to operation, and the usual test is a percentage of link or junction flow rather than an absolute number of vehicles.

Propose the threshold in the note, along with the junctions that meet it and, briefly, the junctions that do not. Listing the excluded junctions with the flows that justify excluding them is what stops an officer adding them later.

Think about the junctions that are already operating at or beyond capacity. A junction with a queue at peak will show a worse result from a small increment, and an authority is entitled to want it assessed even where the percentage test is not met. Better to include it and control the modelling than to have it imposed after submission.

Where the site access is new, that junction is assessed in every case, along with the first junction upstream and downstream on the network.

Base year, assessment years and committed development

The base year is normally the year of the traffic surveys. Where existing counts are used, state their year and the growth factors applied to bring them forward.

Assessment years usually include the year of opening and a future year some years after, reflecting full occupation plus a period of growth. Phased schemes need a year per phase where phases are years apart. Agree these in the note, because reworking a model for a different year is not a small edit.

Committed development is the list that grows. It should cover permitted but unbuilt schemes that will load the same junctions, and allocations where the authority expects them to come forward within the assessment period. Ask the authority for its list rather than building your own, then confirm what you have used. A committed development list agreed in writing is a defence against the objection that the cumulative position has been understated.

Growth factors come from the national traffic forecasting dataset unless the authority has its own model. Say which you are using and at what level of geography.

Trip generation, distribution and assignment

Set out how trip rates will be derived, the database categories, the filters and the date range. Where a specialist land use does not fit the standard categories, say how you will handle it and offer an alternative source.

Distribution needs a method and a sense check. Census journey to work data at a suitable geography is the usual starting point for residential schemes, with a gravity model or an observed pattern for retail and employment. State the method in the note so it is not argued about later.

Assignment should say which routes development traffic is assumed to use and why. On a constrained network, the assignment assumption can matter more than the trip rate, and an authority that disagrees with it will reject the conclusions rather than the numbers.

Include the treatment of internal trips, linked trips and pass-by trips where the land use justifies them, with the evidence you will rely on. These reductions are legitimate and they are also the ones most often applied without support.

Surveys, neutral months and collision data

Traffic counts and junction turning counts have to be taken in neutral conditions. That means avoiding school holidays, the weeks either side of them, August, December and any period affected by roadworks on the network or a local event.

Name the survey window in the note and the fallback if weather or roadworks intervene. Where surveys already exist, from another scheme or the authority's own monitoring, propose using them and say how old they are.

Collision data is normally requested for the most recent five-year period on the network within the study area, from the authority or the national dataset. Agree the period and the extent in the note, because a longer period on a wider network changes the picture. How that data should be handled once you have it is covered in the note on using personal injury collision data properly.

Parking surveys, where on-street capacity is in issue, follow the established overnight and weekend methodology and have their own neutral period rules. The approach to justifying provision above or below the local standard is set out in the guidance on evidencing parking provision.

Getting the note agreed in writing

Send the note as a document, not as an email body, and ask for written confirmation of agreement or of any changes. A reply that says content noted is not agreement, and it will not help you later.

Where the authority will not engage without a fee, take the planning performance agreement or the chargeable pre-application route. The cost is small against a re-modelling exercise, and the meeting that comes with it usually surfaces the local issue that no dataset would have told you about, such as a school crossing patrol or a lorry ban on a preferred route.

Keep the agreed note as an appendix to the submitted assessment. When a consultee queries the study area 14 weeks later, the answer is a page reference rather than a recollection.

When the authority changes its mind

It happens, usually because the officer has changed, a new scheme has been permitted nearby, or a member has raised a junction at committee.

Deal with it in three steps. Ask for the reason in writing. Check whether the change is material to the conclusions or merely additional, because adding a junction that comfortably passes is faster than arguing about it. Then quantify the cost and time, and put that to the authority alongside the agreed note.

Where the new request would change the outcome, it deserves a proper response rather than compliance. An assessment scoped in agreement, carried out to the agreed method and appended with the correspondence, is a strong position at appeal, and inspectors notice when an authority has moved the goalposts.

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