How to read a transport assessment before you bid

01 What a transport assessment is, and when one is required

A transport assessment (TA) is the study that sets out how a development will be reached, how many trips it will generate, what that does to the surrounding network, and what has to be built or committed to in order to make it acceptable. It supports the planning application and is negotiated with the local highway authority, which on most sites is the county or unitary authority, and with National Highways where a strategic road is affected.

National planning policy asks for an assessment where a development would generate significant amounts of movement. The thresholds that trigger one are set locally, so the same warehouse can need a full assessment in one authority and a lighter statement in the next. For big-shed logistics the question is usually not whether there is a TA in the data room, but whether the one that is there still describes the scheme you are bidding on.

In London the picture is layered. Schemes affecting the Transport for London road network or the strategic network are assessed against TfL's guidance as well as the borough's, with more weight on trips by every mode and on street quality, not just on whether a junction has spare vehicular capacity.

02 Assessment or statement: which document you are holding

The two documents are not interchangeable. A transport statement is a proportionate summary used where the transport effects are limited: a description of the site, its accessibility, an estimate of trips and a light touch on mitigation. A transport assessment is the fuller evidence base, with survey data, junction modelling, a cumulative assessment and a negotiated mitigation package. A travel plan is a third thing again: the ongoing commitment to manage how people get to the site once it is occupied.

The distinction matters commercially because the lighter document leaves more unresolved. If the vendor's pack contains a transport statement for a scheme you intend to intensify, or to convert to a use with a different trip profile, expect the highway authority to ask for a full assessment. That is fee, survey season and negotiation time, and it sits on the critical path to a consent.

03 Trip generation: the number that decides the scheme

Everything downstream in a transport assessment is driven by the trip generation forecast, and that forecast is a judgement, not a measurement. It is usually built by taking observed trip rates from comparable sites, most often via the industry TRICS database, and applying them to the floorspace and use proposed. Choose different comparison sites and you get a different scheme.

On industrial and logistics this is where to spend your reading time. Ask which comparison sites were used and whether they resemble the operation the site will actually host. A regional distribution centre running multiple shifts around the clock generates a very different profile from a multi-let trade estate: different peak hours, a different HGV share, different staff parking demand, and a different answer on whether the network pinch point falls inside the modelled peak at all. A trip rate drawn from general industrial floorspace will understate a modern fulfilment operation.

Check too what the assessment counted as the baseline. Where a site is already occupied, existing trips are often netted off, so the assessed impact is the increase rather than the total. That is legitimate, but it means a vacant or lightly used site can carry a much larger assessed impact than the floorspace alone suggests.

04 Access, servicing and the site layout

The assessment also fixes the physical arrangement the consent depends on: where the access sits, what visibility splays it needs, how HGVs turn into and around the yard, and how many car and cycle spaces are provided. These are the lines that quietly constrain the developable area.

Look for the swept path analysis for the largest vehicle the operator will use, the yard depth the layout assumes, and whether refuse, fire and delivery access all work on the same plan. Look at parking provision against the local standard and against what an occupier will demand, including electric vehicle charging and cycle parking, because a shortfall becomes either a design change or a reason for objection. And read the construction traffic management section, which on a constrained urban site can carry real cost and real neighbour risk.

05 The mitigation package: section 278, section 106 and travel plans

A transport assessment ends in commitments, and those commitments are where a bid gets priced. They arrive in three forms.

A section 278 agreement under the Highways Act 1980 is the contract with the highway authority for works to the existing public highway: the access, the junction, the signals, the widening. It carries design approval, technical and inspection fees, and normally a bond for the value of the works. Its sibling, a section 38 agreement, covers new estate roads that the authority will adopt.

A section 106 obligation may carry financial contributions towards off-site transport measures, bus services or monitoring. Unlike the section 278 contract, a section 106 is registered as a local land charge and binds successors in title, so it follows the site to you.

A travel plan is the long tail: targets for mode share, monitoring surveys, sometimes a financial penalty or a bond if targets are missed, running for years after occupation. It is usually secured by condition or by the section 106, and it is routinely underestimated in an appraisal because it looks administrative rather than financial.

For each of these, the questions before a bid are the same three. What is the agreed scope? Is there a cost or a bond figure, or is it still open? And is delivery tied to a trigger, such as a condition preventing occupation until the works are complete, that could hold up income?

06 Red flags to catch before you bid

Some findings should change your number rather than your notes. Watch for an assessment written for a different scheme, whether a different floorspace, a different use class or a different unit mix from the one being marketed. Watch for baseline surveys from an atypical period, or counts old enough that the highway authority will want them redone.

Then look at what the mitigation depends on. Junction improvements that need third-party land the seller does not control are a deal risk, not a cost line. A section 278 with no agreed design or cost, or an unquantified bond, leaves an open-ended number in the appraisal. An unimplemented highways agreement attached to a lapsed or superseded consent tells you the transport case has to be made again. And a travel plan with monitoring obligations running well past practical completion is a management liability that belongs in the hold period, not the build cost.

None of these is automatically fatal. The job before a bid is to turn each one into a cost, a programme risk or a reason to walk, and to be certain none of them are sitting unread in an appendix.

07 Frequently asked questions

What should a transport assessment include?

A description of the development and its access arrangements, baseline data on existing traffic and safety on the surrounding network, an assessment of walking, cycling and public transport options, a trip generation forecast across all modes, junction and network modelling of the effect of those trips, the cumulative effect of other committed development, parking and servicing provision, construction traffic management, and the mitigation and travel plan measures proposed to deal with what the modelling shows.

What is the difference between a transport assessment and a transport statement?

A transport statement is the lighter document, used where a development's transport effects are limited. A transport assessment is the fuller evidence base, with modelling and a mitigation package, required where a development generates significant amounts of movement. The thresholds are set locally rather than nationally, so a scheme that only warranted a statement in one authority can require a full assessment in another. If the data room holds only a statement, check that the highway authority has accepted it for the scheme you intend to build.

How much does a transport assessment cost?

It varies with the scale of the scheme and how much modelling the highway authority expects. A statement on a small unit is a modest fixed fee; a full assessment for a large distribution scheme, with traffic surveys, junction modelling and several rounds of negotiation with the highway authority, costs considerably more. For a bid the fee is rarely the point. What matters is the mitigation the assessment commits the scheme to, because the highway works and the travel plan obligations are the numbers that reach the appraisal.

How long is a transport assessment valid for?

There is no statutory shelf life, but the evidence underneath it ages. Baseline traffic counts more than a few years old are routinely challenged, committed development in the area changes the cumulative case, and local transport policy moves. An assessment written for an earlier consent may need its surveys refreshed and its modelling rerun before it can support a new application, which is programme time to allow for rather than an assumption to carry into a bid.

What is a section 278 agreement?

A section 278 agreement, under the Highways Act 1980, is the contract between a developer and the local highway authority that allows works to be carried out to the existing public highway at the developer's expense. On an industrial or logistics scheme it is how the site access, the junction improvement and any signalling or widening the transport assessment recommends actually get built. It usually comes with design approval, a technical fee, an inspection regime and a bond or other security for the cost of the works.

What is the difference between a section 38 and a section 278 agreement?

A section 278 agreement covers works to a highway that already exists, such as a new access or a junction upgrade. A section 38 agreement covers new roads built as part of the development that the highway authority then adopts and maintains at public expense. Many schemes need both: a section 278 to connect to the network and a section 38 to hand over the estate roads. Both are under the Highways Act 1980, and both usually carry a bond until the works are complete and adopted.

What happens if there is no section 38 agreement?

The estate roads stay private and unadopted, and the owners of the land they serve keep the cost of maintaining, lighting and insuring them indefinitely. That is a legitimate way to run an industrial estate, and plenty do, but it needs to be a decision rather than a discovery. Check who actually owns the road, whether every unit has a registered right of way over it, how the maintenance cost is collected from the occupiers, and what condition the surface and drainage are in. An unadopted road with no working mechanism for recovering its upkeep is a service charge dispute and a repair liability nobody has budgeted for.

How long does it take for a council to adopt a road?

Longer than most programmes assume. Adoption follows the section 38 agreement in stages: the design is approved, the road is built to the authority's specification, it is inspected, and then a maintenance period runs, usually measured in months to a year or more, before the authority takes it over and the bond is released. Any defect found along the way restarts part of that clock. For a bid the consequence is that a scheme can be built, occupied and income producing while the estate roads are still unadopted and the bond is still outstanding, so ask where in that sequence the site sits rather than whether an agreement exists.

Do section 278 agreements run with the land?

Not in the way a section 106 obligation does. A section 106 planning obligation is registered as a local land charge and binds successors in title. A section 278 is a contract with the highway authority, normally backed by a bond, so on a sale it has to be dealt with expressly, by novation or by a fresh agreement. What does follow the site is the planning condition that ties occupation or commencement to the highway works being delivered, which is why an unbuilt section 278 is a live obligation for a buyer even when the contract sits with someone else.

Do you need planning permission for a section 278?

A section 278 agreement is not a substitute for planning permission. In practice the highway works are authorised by the planning permission for the development, and the section 278 is the legal mechanism for carrying them out on land the highway authority controls. Works that fall outside the red line of the consent may need their own permission, or may be covered by the highway authority's own permitted development rights. Check that the works the agreement describes match the works the consent authorises.