Edinburgh to Perth
The M90 is the oldest motorway in Scotland and remains a very important piece of its road network. Linking the cities of Edinburgh and Perth, it originally began at Admiralty, near Dunfermline and ran for thirty miles, bypassing the towns of Kelty, Kinross and Bridge of Earn.
It is primarily a dual two lane motorway and was constructed in several contracts between 1964 and 1980. With the construction of the Queensferry Crossing in 2017, the M90 was extended southwards to Kirkliston, connecting with the M9 motorway for the first time. It has many interesting engineering features along its route.
A special road, bypassing Kelty and Kinross was first proposed in the 1940s to improve connections between the planned Forth Road Bridge (FRB) and Perth. The old A90, which was mostly single carriageway, passed through a number of towns and included a narrow, winding section at Glenfarg. Drivers seeking to cross the Firth of Forth via the centuries old ferry service also faced long delays. The Inverkeithing to Perth section of the proposed motorway was included in a 1963 government White Paper focussed on Scotland's economic development. The Paper outlined plans to build a motorway from the FRB to Milnathort by 1970.
Construction of the Forth Road Bridge began in November 1958, and included new approach roads to the north and south. The majority of this new road was built as all-purpose dual carriageway and numbered A90, however the northernmost two miles were built to motorway standards. The FRB and its approaches were completed in September 1964, with the M90 becoming Scotland's first motorway. This short motorway initially operated with no hard shoulders and terminated on the A90 at Duloch.
The northern approaches to the FRB included the construction of the A823(M), a short spur connecting the M90 at Masterton Interchange with the A823 in Rosyth. At just under a mile in length, it is one of the shortest motorways in the UK. It was originally intended that the route would be extended eastwards to Kirkcaldy and westwards to Kincardine Bridge as part of the East Fife Regional Road (EFRR). It was decided some years later that the EFRR would be located in a new corridor to the north, eventually built as the A92 from Halbeath to Kirkcaldy. South facing, free-flow slips were constructed in 1998, connecting the M90 directly to the A92.
M90 Construction Summary
Forth Road Bridge - North Approaches
1C - 2
4th September 1964
Crossgates, Cowdenbeath & Kelty Bypass
2 - 5
1st December 1969
Kinross & Milnathort Bypass
5 - 8
13th December 1971
Muirmont to Moncrieffe Hill
9 - 10
27th October 1977
Craigend to Broxden
10 - 12
24th May 1978
10 - 11
28th September 1978
A92 Halbeath Interchange
27th March 1998
M90 Intelligent Transport System
1 - 2A
4th December 2012
M9 J1A Upgrade*
M9 - 1
1st February 2013
1A - 1B
4th September 2017
The M90 was extended northwards from Duloch to a temporary terminus at Lochran, near Fruix in 1969. This seven mile section provided a bypass of Crossgates, Cowdenbeath & Kelty when it was opened by Lord Hughes, the then Minister of State for Scotland.
This section of the motorway runs across old mining ground with several shafts and workings requiring treatment before construction could begin, indeed several overbridges were built to withstand any potential earth movement. The road was initially constructed with no hard shoulders, although laybys were provided at one mile intervals. They were eventually added in the mid-1970s, having been allowed for in the original design. The project was designed by Fife County Council with input from W.A Fairhurst & Partners.
The project made use of "RRL Reflector Kerbs", an experimental system developed by the Road Research Laboratory to use vehicle headlights to highlight the edge of the road. The trial was ultimately deemed unsuccessful, but they were used extensively on the A9 between Perth & Inverness and the A77 between Kilmarnock & Prestwick.
The Kinross & Milnathort Bypass, opened in 1971 by George Younger MP, extended the motorway further. This eight mile section, found today between Junctions 5 and 8, has some notable features. In keeping with earlier contracts, this section was constructed without hard shoulders. The stretch remains the longest section of motorway in Scotland without them, although emergency laybys are present every 1/4 of a mile. The road was constructed with "unreinforced concrete" pavements, the first of their kind in the UK. Their use was part of an experiment by the Scottish Development Department, though it was overlaid with bituminous material between 2006 and 2017. This section of the motorway terminated north of Junction 8, connecting to the then A90 at Glenfarg.
Completion of the M90 between Arlary and Bridge of Earn was delayed. A Public Local Inquiry, held in 1971 to consider the proposed route of the motorway at Glenfarg, and the Oil Crisis of 1973 were amongst the contributing factors.
The inquiry was ordered due to concerns about the motorway's effect on the landscape, specifically at Balmanno Hill, and the controversial closure of the Glenfarg Railway Line in 1970 to make way for the road.
Due to the challenging geography, particularly at Balmanno Hill, the section between Junctions 8 and 9 was split into two contracts. The first section, completed in 1977, extended from Junction 8 to a temporary connection with the A90 at Arngask. The motorway is constructed immediately east of Glenfarg Village, resulting in long rock cuttings and the excavation of 500,000 cubic metres of material. This was the first section of M90 built with hard shoulders as part of its original construction.
The second section, from Arngask to the existing motorway at Bridge of Earn, was opened by Lord Mansfield in 1980, the last of the original M90 projects to be completed. The challenging geography at Balmanno Hill resulted in a curve of 694m radius, one of the sharpest on the UK motorway network. This was necessary to allow the motorway to descend gradually into the Earn Valley via the route of the former railway line.
Between Bridge of Earn and Friarton Bridge, the M90 climbs to Craigend Interchange, completed in 1977. The embankments at Bridge of Earn were complex to construct, due to silty ground, and were built at a rate of half a metre per month to avoid subsidence. Work on this began some time before the main construction contract. This section also required an incredibly high rock cutting at Moncrieff Hill. At 54m, it is one of the highest rock faces on the UK motorway system.
Further large excavations were required for the slip roads of the interchange and construction was further complicated by the presence of the Moncrieff Railway Tunnel below the site. Blasting was restricted and vibrations were monitored by the use of extensive recording equipment. The M90 passes through Craigend on a compound curve, the northern part of which is 694m, the same as at Balmanno Hill, and the southern, 520m.
At Craigend, the motorway splits into two sections, each completed in 1978. One proceeds westwards towards the A9 at Broxden Roundabout and the second continues northwards towards Friarton Bridge and the A90.
The western stretch is notable for its gradient uphill of nearly 5% and downhill of nearly 6% (the spur to Friarton Bridge), the steepest of any motorway in the UK. The eastern section crosses the River Tay at Friarton Bridge, and was originally numbered M85.
The M85 was renumbered M90 in 1994, as part of the upgrading of the Perth to Aberdeen road to dual carriageway standards. The change was made to create a continuous route which was given the A90 number. The M85 had been one of the UK's shortest motorways.
Friarton Bridge, designed by Freeman Fox & Partners, is one of the longest sections of elevated motorway in Scotland with a total length of 831m. A twin steel box girder bridge with nine spans and a clearance of 25m above the River Tay, it has a main span of 174m. Eight reinforced concrete piers each support a single carriageway, with Piers 6 & 7 (the main river span) being cross connected at the top by portal beams. The southern portion of the bridge is curved with a radius 690m and a maximum super-elevation of 7%. The bridge was built by Cleveland Bridge &
Over 2km of new dual carriageway was constructed at the northern end of the bridge. This included the Barnhill Interchange, a unique design utilising an open ended roundabout to allow mostly free-flow movements. The bridge's approaches were opened in advance of the main crossing in October 1976 and were built by Shellabear Price Ltd.
Junctions on the M90 are numbered from south to north, from the M9 Junction 1A (Kirkliston) to Junction 12 (Broxden). The first two miles of the route were constructed as a spur of the M9, completed in 1970 and 2007. The spur was upgraded and renumbered M90 in advance of the completion of the Queensferry Crossing, with work including the construction of north facing slip roads on the M9 at J1A. It is constructed to rural motorway standards and has two lanes in each direction.
At Junction 1 (Scotstoun), the motorway merges with the A90 via a fork junction and widens briefly to dual three lane carriageways. This continues to Junction 1A (South Queensferry) which is a full access roundabout at the A904.
After crossing the Firth of Forth via the Queensferry Crossing, Junction 1B (Ferrytoll) provides access to Inverkeithing & Rosyth. A large Park & Ride facility is provided to the east of the junction. The junction also allows for temporary access to the Forth Road Bridge in the event of closures of the Queensferry Crossing. Junction 1C (Admiralty) marks the start of the original M90, and is a full access roundabout connecting with the A985 and A921. Between these junctions, the motorway has three running lanes in each direction with intermittent hard shoulders.
Less than 400m north is Junction 2 (Masterton), a partially completed Octopus type design allowing access to Dunfermline via the A823(M). North of Masterton, the M90 narrows to dual two lane carriageway, with the southbound hard shoulder featuring a controlled bus lane on approach to Queensferry Crossing. The bus lane was the first of its type on the Scottish motorway system when completed in late 2012. An extensive intelligent transport system was installed as part of the project.
Junctions 2A and 3 are part of Halbeath Interchange. Junction 2A allows free flow access onto the A92 to Kirkcaldy via east facing slip roads. More than half of the traffic using the M90 between Junctions 1B and 3 joins or leaves the motorway at this point. Junction 3 is a roundabout interchange and allows access to Dunfermline, Duloch and the large Amazon warehouse located next to the motorway. North of here, the M90 becomes rural, passing Hill of Beath and Kelty to the west. Junction 4 (Cocklaw) is a full access fork allowing access into Kelty on the B914.
North of Junction 4, the M90 passes through predominantly agricultural land. It passes west of Loch Leven before bypassing the towns of Kinross and Milnathort. On passing Lochran Farm, the motorway loses its hard shoulder, although frequent lay-bys, some equipped with emergency telephones are provided. Junction 5 (Gairney Bridge) is a full access fork junction with the B9097; and Junction 6 (Kinross) is a roundabout interchange providing access to Kinross and the motorway service area at the A922 and A977. The service area was completed in early 1980s and is currently operated by Moto.
Junction 7 (Hilton) is a half diamond interchange with north facing slip roads. It provides access to the A91 west of Milnathort. Junction 8 (Arlary) is a fork type junction which connects to the A91 towards St. Andrews via another fork junction west of Mawcarse. North of here, the motorway regains its hard shoulders and climbs towards the Ochil Hills. It curves around Balmanno Hill before descending to Bridge of Earn at Junction 9. This junction is a diamond interchange type, connecting to the A912 towards Bridge of Earn and central Fife.
Junction 10 (Craigend) is the most northerly three-level interchange in the UK and is where the M90 splits into two sections. The western spur meets the A9 and A93 at J12 (Broxden Roundabout), the most northerly section of motorway in the UK. The eastern stretch passes below Craigend Interchange and crosses Friarton Bridge, becoming the A90 dual carriageway north of J11 (Barnhill). This junction is a semi-modified roundabout interchange and allows for journeys into Perth along the A85.
From the Archive
This article was first published in January 2022 and updated in October 2022. With thanks to Ronnie Land, formerly of Babtie, Shaw & Morton