M8

The first and last east-west motorway north of the M62, the M8 links up Edinburgh and Glasgow in style. It starts at the A720 Edinburgh City Bypass, powers across Scotland's central belt almost in a straight line, and dives right into the absolute centre of Glasgow. The most audacious urban motorway in the UK then blasts a path through the city and out the other side, connecting with the Erskine Bridge before returning traffic to the A8 towards Greenock.

Otherwise completed in 1995 with the construction of the section from the M9 to its terminus at the A720, the M8 remained unfinished thanks to a glaring six-mile gap between Newhouse and Baillieston, and for decades Scotland's most important motorway was interrupted between junctions 6 and 8 by a section of old A8 dual carriageway that struggled to cope with its traffic load. This put it in the same club as the M74 and M80 as a Scottish motorway with a permanently missing section - but by 2011 those roads had been completed. The long-delayed M8 completion project has now delivered the goods, with the final section of this motorway opened in April 2017.

A string of public artworks were placed along the side of the M8 between Edinburgh and Glasgow during the 1990s, partly to add some interest to the journey, thanks to something called the M8 Art Project. At various points motorists catch sight of the Sawtooth Ramps, a row of four square grassy pyramids; the Heavy Horse, a wire mesh horse sculpture by the artist who went on to design the Kelpies; Big Heids, a row of three enormous red busts modelled on random people from the streets of Motherwell; and the strangest of all, The Horn, a tall curved horn mounted beside the motorway that can be heard playing music, poetry and quotations to passing traffic.

The section through central Glasgow is notorious and thrilling. It's manically busy, forming two sides of a never-finished inner ring road, and the mix of local, long-distance and commuter traffic can be a recipe for chronic congestion. It is five lanes wide in places, but at crucial points in the centre narrows down to two. The knotted tangle of junctions includes Britain's closest exits and more than one unusual right-hand sliproad. It was designed and built following the design guidance for American urban freeways, and it shows: the urban M8 is nothing like other UK motorways and instead is clearly and visibly straight out of Los Angeles. Glasgow is unique among the UK's major cities in having no ring road of any significance and instead carrying through traffic right through its heart.

Relief for the city centre section arrived not in the form of a ring road or bypass for Glasgow but instead with more urban motorway building - something unthinkable elsewhere in the UK but which happened here as recently as 2011. The new M74 extension was built to calm the M8's troubles, bypassing the central Glasgow section completely and allowing traffic travelling from one side of the city to the other to avoid the city centre for the very first time. It's mostly elevated, pushing its way through the industrial areas south of the Clyde.