Commuted sums, explained to a normal person

Somewhere near the end of a Section 38 or Section 278 agreement, a number appears that nobody mentioned at the planning stage. It's called a commuted sum, and it's worth understanding before it understands you.

Here's the idea. When a developer builds a new road and hands it to the highway authority, the council takes on the job of looking after it for ever. Standard tarmac, standard kerbs and standard lighting are covered by the normal maintenance budget. Anything beyond standard isn't, so the council asks for a one-off payment to cover the extra cost of maintaining it over the long term. Usually that's thirty years, sometimes longer for structures. That payment is the commuted sum.

What tends to attract one:

• Fancy surfacing. Block paving, resin, coloured surfacing. Lovely on the day, pricey when it needs lifting to fix a service.
• Trees and planting in the highway. Someone has to prune them, water them and replace the ones that don't make it.
• Extra street lighting, or columns and lanterns that aren't the council's standard kit.
• Features. Raised tables, build-outs, anything with a bit of character.

None of this is the council being awkward. They're pricing a promise to look after something for a very long time with a budget that isn't growing. Fair enough.

The trick is not to be surprised by it. We raise commuted sums early, before the layout is fixed and the architect has fallen for the herringbone paving. Often the answer is a small design nudge: a standard material here, a tree in a garden rather than a verge there, planting that's in the adopted highway only where it really earns its place. The road still looks good, and the number at the end stays sensible.

And where a feature matters, we'll help make the case for it with the number alongside, so the client decides with their eyes open.

If you've got an agreement coming up and want to know what the commuted sum might look like before anyone else tells you, give us a shout.