Abnormal Load Bay
An abnormal load bay (often shortened to 'AIL bay' after the industry term, 'abnormal indivisible load'), is a parking area that is provided for very large vehicles that won't fit into the normal HGV parking spaces, and probably won't even fit into regular roadside lay-bys. They sometimes use the more catchy name of "long loads".
These bays are a mandatory feature of motorway service areas, and should be kept clear of cars and HGVs. In practice they are almost always used by vehicles who couldn't or didn't want to find the main parking area.
The bays only need to be able to handle one abnormal load and its assistance vehicles. These vehicles always plan their journeys in advance and factor in the necessary rest breaks. The abnormal load bay is usually attached to the main circulatory road, because abnormal loads can't handle narrow car park aisles.
They are not very interesting, but documentation talks about "AILs", so we wanted to explain.