Salt, Slopes and Second Thoughts: The Quiet Arithmetic Behind London's Winter Routes

Every October, in depot offices from Croydon to Enfield, a map is quietly redrawn. It is not a political map, or a planning map, but something more immediately consequential: the list of streets a borough will salt before dawn. By the time the first hard frost of the 2026-27 season arrives, that list will already be fixed, and the households on it — or off it — will have had almost no say in the matter.

A duty, but not an absolute one

English highway authorities have a statutory duty under the Highways Act 1980 to take reasonable care that roads are not dangerous to traffic. In practice, that has long been interpreted as a duty to act reasonably, not a guarantee of bare tarmac everywhere. The courts have consistently held that councils cannot be expected to treat every mile of adopted highway, and the law has been read accordingly.

That legal latitude is where the politics begins. London's 33 boroughs, plus Transport for London for the red routes, each publish a winter service plan setting out which parts of their network are treated first. The plans are public documents, but they are rarely read until something goes wrong.

What makes the cut

Broadly, the same criteria recur across the capital. Bus corridors rank near the top, because a single treated artery can keep dozens of services running. So do principal roads, steep hills, access routes to hospitals, and approaches to major stations. Some boroughs also include school streets adjacent to special educational needs provision, and routes used by community transport.

What almost never appears on a first-round list is the ordinary residential cul-de-sac. Officers are candid about why: salt is cheap, but the labour, vehicles and time are not, and a spreader sent down a side street is a spreader not sent down a hill.

In a typical outer London borough, the priority network covers somewhere between a quarter and a third of the total road length. In inner boroughs with dense bus networks, it can run higher. The remainder is treated reactively, if at all.

The ambulance question

A recurring point of friction is whether ambulance routes should be formally designated. London Ambulance Service does not have a statutory right of priority over the gritting list, and boroughs vary in how far they consult it. Some invite the service into the drafting process; others rely on hospital access roads alone.

This is where the priority map becomes more than an operational document. A paramedic crew unable to reach a steep residential street in a freezing January is not a theoretical problem, and the absence of a formal designation does not make it any less real. Several boroughs have quietly widened their networks in recent years following pressure from scrutiny committees, though the pattern is uneven.

Paying for preparedness

Winter maintenance is funded from general highways budgets, with salt stocks bought ahead of the season. The economics are unforgiving: salt bought in bulk in autumn is far cheaper than salt sourced in the middle of a cold snap, and a full salt barn is a form of insurance that shows up on no balance sheet.

The 2026-27 plans lodged with borough cabinets point to broadly stable allocations, with several authorities noting cost pressure on vehicles and fuel rather than on salt itself. The deeper issue is staffing. Gritting is largely delivered by drivers who do other work the rest of the year — refuse, street cleansing, parks — and a depleted depot roster narrows what can be achieved in a six-hour window.

The communications problem

When snow arrives, the first question residents ask is not about the plan but about their street. Boroughs increasingly publish live treatment logs and route maps, but the information is often fragmented across council websites, and the language — "priority one", "secondary network" — does little to explain why one road was treated and the next was not.

Some authorities have begun sending postcodes to a lookup tool so residents can check their own street. It is a modest innovation, but it shifts the conversation from general grievance to specific explanation, which is usually a good thing for trust.

Where the map stops

There is a temptation to see the gritting list as a technical matter best left to engineers. But the list is a set of priorities, and priorities are choices. A borough that treats its bus corridors first is making a judgement about the many over the few; a borough that adds a steep residential hill is making a judgement about risk over volume. Neither is wrong. Both deserve to be argued about in public rather than settled in a depot.

As the capital enters another winter, the salt spreader remains one of the most consequential vehicles in local government. It does not decide policy. It merely carries out a decision taken months earlier, on a map few residents have ever seen.

Residents wanting to know whether their road is on the list can find their borough's winter service plan on its council website, usually filed under highways maintenance rather than under anything resembling weather.