Section 38 adoption and the commuted sum negotiation
Bonds, inspection fees and commuted sums decide the real cost of adopting estate roads under section 38 of the Highways Act 1980. Here is how each is set and where the negotiation sits.
The section 38 adoption cost on a small estate is rarely the construction bill. It is the bond, the technical approval and inspection fees, and the commuted sum the highway authority asks for to take on long term maintenance. Those three items are negotiable in part, they are set by each highway authority's own published schedule, and they land at the point in a scheme where the land price is already fixed.
Section 38 of the Highways Act 1980 is the agreement under which a highway authority agrees to adopt a road built by someone else, so that it becomes highway maintainable at public expense. Section 278 of the same Act covers works to an existing highway, such as a new junction or a footway crossing. Most residential schemes need both.
What adoption under section 38 actually involves
The agreement is a deed between the developer and the highway authority, usually secured before the road is built and often required by a planning condition or an obligation under section 106. It fixes the specification, the programme, the security and the maintenance arrangements.
The sequence runs roughly like this:
- Pre-application discussion with the highway authority's development management team, ideally before the layout is fixed.
- Technical approval of construction drawings against the authority's design guide, with Manual for Streets informing geometry and street character on residential roads.
- Execution of the section 38 agreement, with the bond or other security in place.
- Construction under inspection, with the authority charging for inspections.
- A provisional certificate when the works are complete to the authority's satisfaction.
- The maintenance period, during which the developer remains liable for defects.
- A final certificate and adoption, with release of the bond.
The point to hold on to is that adoption is a specification question long before it is a money question. A layout that the authority will not adopt, because the carriageway width is wrong or the turning head will not take a refuse vehicle, gets expensive at technical approval rather than at planning.
Fees, bonds and inspection charges
Highway authorities set their own charges and publish them, usually as a percentage of the estimated works value for technical approval and inspection, plus legal fees for preparing the agreement. The percentages differ between authorities, so take them from the authority's current published schedule rather than from the last scheme you did in a different county.
The bond is the item that catches developers out. It is security for the cost the authority would face in completing and correcting the works if the developer failed partway through, so it is sized against the full works value, sometimes with an uplift. A surety bond costs an annual premium and ties up facility headroom; a cash deposit ties up cash. Either way it sits on the balance sheet from the date the agreement is signed until the final certificate, which on a phased site can be several years.
Ask the authority early whether it will accept a staged bond that reduces as phases are certified. Many will. Few volunteer it.
How commuted sums are calculated
A commuted sum is a capital payment representing the future maintenance cost of assets the authority would not otherwise carry, or that cost more to maintain than a standard adopted road. Common triggers are structures such as retaining walls and culverts, pumping stations, surface water drainage features within the highway, street trees, non-standard surfacing, verges and any lighting above the authority's standard specification.
The method is usually a whole life calculation: the authority takes the expected maintenance and replacement events over a design life, applies its current unit rates, and discounts back to a present value. Design lives of several decades are common for structures. Because every input comes from the authority's own rate schedule, the sum is not a figure you can estimate nationally, and any consultant who quotes one without naming the authority is guessing.
Illustrative example: a scheme with a single adopted retaining wall, two attenuation features in the highway verge and eighteen street trees will typically attract three separate commuted sums, each calculated on a different design life. Removing the attenuation from the adopted highway and placing it on managed open space can remove one of them entirely, which is a layout decision taken at the design stage.
What you can do is reduce the exposure. Specify to the authority's standard details wherever the scheme allows. Keep unusual assets out of the adopted extent. Where the authority's drainage team wants a feature adopted and the lead local flood authority wants it managed differently, resolve that before you submit, because the Drainage Strategy is where the split of responsibility gets written down.
The maintenance period and what it costs
Twelve months is the usual maintenance period after the provisional certificate, though authorities take longer where planting or structures are involved. During it the developer fixes defects, keeps the bond in place and continues to carry the road on its own insurance.
Budget for three things: a defects allowance, the bond premium for the extra period, and the cost of keeping a site presence. On a site where the last plots sell slowly, the maintenance period can outlast the sales programme, and the road surface takes damage from construction traffic on the final phases. Sequencing the wearing course late is standard practice for exactly this reason, and it needs to be written into the Construction Traffic Management Plan rather than assumed.
Where a private road costs less, and where it does not
A private road avoids the bond, the inspection fees and the commuted sums. That is a real saving, and on a cul-de-sac of six houses with no through movement it can be the sensible answer.
It is a poor answer at scale. A private estate needs a management company, an estate rentcharge or service charge mechanism, and a funded sinking fund for resurfacing. Buyers' solicitors will raise enquiries. Some lenders ask for a deed of covenant or a road bond before they will lend. And residents who pay council tax and a service charge for the same road tend to lobby the authority for adoption later, at which point the road has to be brought up to adoptable standard at the residents' expense.
| Route | Up front cost | Ongoing liability | Common friction |
|---|---|---|---|
| Section 38 adoption | Bond, fees, commuted sums | Ends at final certificate | Technical approval delays, adoptable layout constraints |
| Private road with management company | Company set up, sinking fund design | Permanent, sits with residents | Lender enquiries, service charge disputes, later adoption requests |
| Hybrid: spine adopted, courtyards private | Reduced bond and sums | Split | Boundary of adopted extent must be drawn precisely |
The hybrid is what most medium sized schemes end up doing. Draw the adopted extent on a plan at the layout stage and hold it, because moving that line after technical approval means redrawing the drainage and the lighting design too.
Budgeting from the outline stage
Put a highways provision into the appraisal at outline, before the layout is designed, and split it into technical approval and inspection fees, bond cost, section 278 works, and commuted sums. Then revisit it at reserved matters when the adopted extent is known.
Two habits help. Ask the highway authority for its current fee schedule and commuted sum policy in writing at the pre-application stage, and date the copy you worked to. And check whether the planning permission ties adoption to a trigger point, because a condition requiring the road to be adopted before occupation of a set number of dwellings can force you into a bond you had planned to avoid. Where the scheme is large enough to need a Transport Assessment, the adoption strategy should be consistent with what that document says about access and servicing.
This is general guidance, not legal advice; check the position with your local highway authority or a qualified professional before relying on it.
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Frequently asked questions
What is the difference between a section 38 and a section 278 agreement?
Section 38 of the Highways Act 1980 covers adoption of a new road built by a developer so it becomes maintainable at public expense. Section 278 covers works carried out to an existing public highway, such as a new priority junction or a signalised access. Most residential schemes with a new estate road need both agreements running in parallel.
How is a commuted sum worked out?
The highway authority takes the maintenance and replacement events expected over an asset's design life, applies its own current unit rates and discounts the total to a present value. Structures, drainage features, street trees and non-standard surfacing each attract their own calculation. Because the inputs come from the authority's schedule, there is no national figure.
Can the bond be reduced as construction progresses?
Many highway authorities will accept a staged bond that steps down as phases reach provisional certificate, which frees up facility headroom on a long programme. It is rarely offered unprompted. Raise it when the heads of terms for the agreement are being drafted rather than after the deed is executed.
How long is the maintenance period before adoption?
Twelve months from the provisional certificate is typical, and authorities often extend it where planting, structures or drainage features are involved. During that period the developer remains liable for defects, keeps the security in place and carries the road on its own insurance. Late laying of the wearing course is standard practice to limit construction damage.
Do private estate roads still need highway authority approval?
The road itself is not adopted, so it is not built to an adoption agreement, but the access onto the public highway still needs a section 278 agreement and the planning permission will normally condition the access design. Buyers' solicitors and lenders will also scrutinise the management company and sinking fund arrangements.
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.