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Maintenance Compounds

Watford Gap works unit.
An example of a depot next to a service station.

Many older motorway services have a Highways England maintenance depot within them, usually signposted as a works unit. This page takes a brief look at why this is.


When the earliest motorways were being designed, it was decided that maintenance facilities should be provided every 12 miles. This figure was based on the capacity of a salt spreading vehicle at the time.

Meanwhile, in another meeting, it was decided that service stations should also be 12 miles apart. As a result, to reduce the number of exits on the motorway network and reduce the time taken to get maintenance depots through the planning process, it was decided depots would be shoehorned into existing service stations. There would be only one at each site. Ideally, they would use land which had been severed by the construction of the services but hadn't been used.

As motorway services are commercial facilities, sometimes their site would be reserved for later use. The depot would still be needed immediately. As a result, the depot would occupy the whole site until if/when the services were ready to be built.

Another advantage of this set-up is that in the 1960s, the Ministry would prepare the site of a forthcoming service station. Using the land was thought to be better than digging it up and leaving it.

Finally, building a maintenance compound at the same time as a service station meant the same architect and construction firm could do all the work. It was therefore decided that the spacing of all motorway maintenance depots would be based on the location of nearby services.


Salt dome.
Salt domes are difficult to disguise.

Service stations started to put more emphasis on giving motorists as relaxing a break as possible, often by taking advantage of their natural landscape. The Ministry quickly learned that there was nothing less relaxing and less scenic than the sight of a salt storage barn, and several motorway maintenance vehicles. This wasn't just frustrating for motorists, but for the operators who were being encouraged to invest in building a service station.

The second complaint from operators was that they were expected to plan their sites to get people safely from the motorway to the car park, but instead they were having to include and maintain wide, sweeping slip roads to get heavy lorries in and out of the depot. When Toddington was originally opened to bids, it's thought that the operators were so fed up of having to incorporate a depot into their design, they simply ignored it.

Finally, the biggest mistake made when designing the original services, surrounded by expensive land, was that they were far too small. Depots were taking away almost a quarter of that land, and it was desperately needed.

For all of these reasons, by about 1966, it was decided depots would no longer be tied into motorway services.

Depots Built

This is not a complete list of motorway maintenance depots (or indeed local authority maintenance depots), many of which are small compounds built at motorway junctions. These are ones which have affected service stations:

Red Herrings

There is one maintenance compound which is often mistaken by enthusiasts for an unbuilt service station, but it isn't. Perry Barr compound beneath the M6 was intended to be a city council maintenance depot, but it was realised that adding a (very tight) connection to the M6 would make it easier for motorway maintenance vehicles to access the nearby Spaghetti Junction. It was never intended to be a service station, or a junction.

A second example isn't well-known at all, but is still worth mentioning. With no land purchased at Redbourn, in 1959 a site was urgently needed to build a maintenance compound for the new M1. The site chosen was M1 J8 at Breakspears. A few years later it was considered as a possible site for a service area, but quickly ruled out because of the junction design.

At the time, Ministers expected all maintenance compounds to be part of a service area, so even they were confused by this anomaly, and some of their documentation wrongly suggests land here had been purchased to be turned into a service area. In 1961, an unrelated firm proposed building a motel here, which had its application refused.