M90 motorway

The M90 is a motorway that runs from junction 1a of the M9, at the south end of the Forth Road Bridge, to Perth, passing Dunfermline and Kinross on the way. It is the most northerly motorway in the United Kingdom, the northernmost point being a spur into the western suburbs of Perth at Broxden.

History

The first section of the M90 opened in 1964 to coincide with the opening of the Forth Road Bridge and Masterton junction (junction 2). The next section, Crossgates – Kelty and Cowdenbeath Bypass, opened on 1 December 1969, with the next section, Kinross and Milnathort Bypass, opening in May 1972.

The final two sections were due to begin construction around 1973/74, but due to the oil crisis, were put on hold. The next section from Arlary (Jct 8 with A91) to Arngask was opened in March 1977, with the final section between Arngask (GlenFarg) and Muirmont opening in August 1980; which connected up with the completed Friarton Bridge and Perth Bypass to Broxden.

Details

M90, North of Kelty at the boundary between Fife and Kinross-shire

The M90's most substantial engineering feature is the Friarton Bridge in Perth, a tall concrete pillared structure which traverses the River Tay. The bridge carries eastbound traffic from Broxden towards Dundee and along the Firth of Tay. The Queensferry Crossing will open as part of the motorway in 2016.

The road constitutes most of the southerly part of the A90 corridor from Edinburgh, through Perth, Dundee and Aberdeen to Peterhead along the North Sea coast.

A large part of the northern section of the motorway follows the route of the former main railway line between Perth and Edinburgh via Glenfarg, Kinross and the Forth Bridge, which was closed in 1970 despite this not being recommended by the Beeching report. It is not obvious when first driving along the road but close inspection of the 1:25,000 scale Ordnance Survey maps of the route illustrates this.

Another unusual feature of the M90 is that the Kinross and Milnathort Bypass, the eight-mile section of the M90 between Fruix and Arlary, was the first motorway in Britain to be constructed using unreinforced concrete pavements. The south-bound carriageway have since been overlaid over by tarmac, whereas the north-bound carriageway remain unchanged.

Near to its northern terminus, the motorway splits into two branches. The construction of this three-way interchange required the removal of over a million cubic yards of material, mostly rock. The motorway bends through more than 90 degrees, on a compound curve partly of 570 yards and partly of 760 yards radius. One branch heads in a north-easterly direction, flowing into the A90 at its end, numbered junction 11. (This branch was formerly the M85 motorway, until the A85 was renumbered as A90.) The other branch forms part of the western bypass of Perth, and meets the A9 at its end, numbered junction 12. The gradient is 4.57% uphill and 5.65% downhill on this section. The slip roads forming this branch merge with shared priority to allow HGVs to maintain momentum on the steep upgrade.The Broxden to Muirmont slip road at the centre of the interchange has a radius of 150 yards, necessitating maximum superelevation of 7%.

Issues

The M90 lacks hard shoulders for an eight-mile section. In this section there are emergency lay-bys at ¼-mile intervals instead.

The M90 here has another of the tightest corners on the UK motorway network, for which some traffic can be forced to slow down. The corner cuts through the northern side of the Ochil Hills and has a curve radius of 760 yards (a recommended minimum of 1,000 yards was standard practice at the time of construction). This corner also coincides with one of the steepest sections of the motorway, for which north-bound [heavy goods vehicles (HGVs) are sign-posted to stay in a low gear and often brake continuously through the turn. South-bound HGVs are normally substantially reduced in speed as they make the incline.

Southern extension

As part of the Queensferry Crossing scheme, the M90 will be extended across the Firth of Forth over a new cable-stayed bridge, connecting to the northern end of the M9 spur at Scotstoun Interchange. The former M9 spur is now part of M90, in preparation for the completion of the crossing.

Junctions

M90 motorway
Northbound exits	Junction	Southbound exits
Perthshire
Glasgow, Inverness, Stirling A9 Crianlarich (A85) Perth A93	J12	Start of motorway
Road continues as A90 to Dundee, Aberdeen and Forfar	J11	Perth A85, Inverness A9 Non-motorway traffic
Perth, Crieff A85		Start of motorway
Branches join
Perth, Stirling, Glasgow (A9)	J10	Perth, Stirling, Pitlochry (A9)
Bridge of Earn, Aberargie A912	J9	Bridge of Earn, Aberargie A912
Kinross-shire
Cupar, St Andrews A91	J8	No exit
No exit	J7	Stirling A91 Milnathort A911
Kinross, Milnathort A977 Kinross services	J6	Kinross, Crook of Devon A977 Kinross services
Cleish, Crook of Devon B9097	J5	Cleish, Ballingry B9097
Fife
Kelty, Ballingry A909	J4	Kelty, Lochgelly A909
Dunfermline A907	J3	Dunfermline A907, Kirkcaldy, Glenrothes A92
Kirkcaldy, Glenrothes A92	J2A	No exit
Dunfermline, Rosyth A823 (M)	J2	Dunfermline, Rosyth A823(M)
Start of motorway	J1	Inverkeithing A921 Kincardine, Glasgow A985
Inverkeithing and Dalgety Bay A921 Kincardine, Glasgow A985 Non-motorway traffic		Road continues as A90 to Edinburgh, M9, M8 to Glasgow, Edinburgh Airport, Livingston and Carlisle

Outside links

• CBRD Motorway Database - M90
• The Motorway Archive - M90
• Pathetic Motorways - M90