M1 Junction 42 to Junction 43 (Lofthouse / Leeds)

This is the busiest stretch of the M1 there is. It is also one of the shortest, and it has no exit, no services and no hard-shoulder running — a mile and a half of five-lane motorway between two motorway interchanges, carrying more traffic than any other measured length of the road.

More traffic than anywhere else on the M1, in a mile and a half

That makes it the 1st busiest of the 42 measured stretches of M1 mainline, and the 39th for the share of its traffic that is lorries. The average across the measured M1 is 119,883 vehicles a day — see how busy the M1 is junction by junction.

Half the traffic leaves before Leeds

Junction 42 is Lofthouse Interchange, where the M1 crosses the M62 — it is junction 29 of the M62 as well. Junction 43 is Belle Isle Interchange, where the M621 peels off towards Leeds city centre. Neither junction gives you a local road: there is no way off this stretch except onto another motorway.

The Department for Transport’s figures show what that means in practice. This stretch carries 159,683 vehicles a day. The M1 continuing east beyond junction 43 carries 79,481. Roughly half the traffic on the busiest stretch of the M1 is not staying on the M1 at all — it is heading into Leeds.

That matters if you are driving it. The M621 takes priority through junction 43, so the default is to be carried towards central Leeds rather than to stay on the M1. Northbound drivers who are not watching the signs end up in the city.

Southbound is the busier direction, and it has been for years

The two carriageways here are not equal. In 2025 the Department for Transport counted 84,469 vehicles a day southbound against 75,214 northbound — southbound carrying about 12% more. That is not a one-year quirk: southbound has been the heavier direction here in every year since 2018.

The bottleneck is the roundabout at the south end

National Highways has published its own assessment of Lofthouse Interchange, and it is blunt. Around 75,000 vehicles move through the junction every day, with “significant queuing at peak times”, and its forecast is 107,000 a day by 2044 producing queues of up to a kilometre on the M62 eastbound approach. The roundabout dates from the 1960s and is signal-controlled.

National Highways consulted in late 2021 on three options, from a replacement roundabout to demolishing it entirely in favour of free-flowing links. Of 841 responses, 84% backed the full free-flow option. The last public update on that consultation was in August 2022, and the scheme does not appear in National Highways’ current list of Yorkshire and North East projects. We could not find any statement that it has been cancelled either — only that it is not currently listed.

Not a smart motorway — and the speed limit changes here

Five lanes each way, and a hard shoulder throughout. National Highways’ own smart motorways map shows all-lane running on the M1 between junctions 39 and 42, but nothing between junctions 42 and 43. The variable speed limits that apply on the approach from the south end at junction 42, and the national speed limit begins again there.

It used to be the end of the motorway, and it used to be privately run

The M1 through here opened on 27 October 1967 and originally ran on into central Leeds. In February 1999 the M1–A1 Link Road opened and the old route into the city was re-designated the M621, which is why the motorway now bends east at junction 43 instead of carrying straight on. The link road was built and maintained under a 30-year private concession that only expired on 25 March 2026, when this length passed back into National Highways’ ordinary maintenance contract.

Traffic figures on this page are Department for Transport road traffic statistics, annual average daily flow for 2025, both directions combined. Annual average daily flow counts how many vehicles use a stretch across the year. It does not measure how fast they travel, so the busiest stretch is not automatically the slowest.