For most of its life, the M90 and its friend the A823(M) were all alone. The route connects Edinburgh, via the Forth Road Bridge, to Perth and the north and north-east of Scotland. Since it first opened in 1964, it has been separated from the rest of the motorway network by the Forth Road Bridge, which was part of the A90 and not a motorway.

A second crossing of the Forth is now under way, which will be classified M90, and in preparation for its opening a formerly anonymous spur of the M9 has already been numbered as part of the M90. That means that the M90 now does technically connect to the rest of the motorway network - though it isn't actually continuous yet!

At the northern end of its route the motorway splits as it approaches Perth, causing an interesting feature. Heading north, the spur route to the A9 is longer than the remaining motorway straight ahead to the north east.

The M90 is only just a motorway. It has some ridiculously sharp corners (including what is reputedly the tightest curve on the motorway network), and large parts of it lack hard shoulders, instead just having frequent lay-bys. This can, of course, be excused given the challenging geography.

Ronnie Land, who worked on the scheme in the 1960s, notes that the three-way motorway interchange south of Perth required the removal of some 900,000 cubic metres (31,783,000 cubic feet) of material. The minimum curve radius used on the route is 694m (2,278ft); a minimum of 914m (3,000ft) was standard practice at the time. Likewise the maximum gradient then permitted by design standards was 1 in 30 (1 in 20 for hilly areas); some of the M90's slip roads are a little steeper than 1 in 17.

In the early 1990s, mass renumbering of roads up the east side of Scotland was carried out to give the route from Edinburgh to Aberdeen one continuous number, A90. This did some strange things to the area south of Perth where the M90 splits.

Before the change, the M90 went up the west side of the fork to meet the A9. As the A90's traditional northern terminus was Perth, this was the end of the line. The A85 passed through Perth on the east-west axis, and went on to Dundee, and so the motorway to the east of Perth, over the Friarton Bridge, was M85. The change caused the M90 designation to switch from the west to the east of Perth, eating up the entirety of the very short M85, in order to connect the motorway to the extended A-Road. The bit it left behind is now signposted '(A9)' northbound and '(M90)' southbound. This means that the northernmost motorway in the UK has no number.

The numbering as it stands now makes more sense than before: the M85 was always the more popular route, and the junction where the three sections of motorway meet south of Perth gives priority to traffic between the south and Dundee.

Start
Edinburgh
End
Perth
Passes
Forth Road Bridge
Connects to
Length
38 miles
Open Junctions Section
Aug 1964 J1-2 Forth Road Bridge Approach
Dec 1969 J2-3 Crossgates → Kelty
Jul 1970 J3-5 Cowdenbeath Bypass
May 1972 J5-8 Kinross and Milnathort Bypass
Mar 1977 J8-8* Arlary → Arngask
Dec 1977 J9-10 Muirmont → Craigend
May 1978 J10-11 Craigend → A90 Opened as M85
Oct 1980 J8*-9 Arngask → Muirmont
Sep 2007 Kirkliston → South Queensferry Opened as a spur of M9

Exit list

Junction   Northbound               Southbound  
11 Dundee
Aberdeen
A90
Perth
A85






A85
NORTH
A90
N/A
LanesLanesLanesLanes Signs LanesLanesLanesLanes Signs
1 mile, 2 lanes  
River or canal Tay River or canal Tay
  1 mile, 2 lanes
10 Perth (N)
Pitlochry
(A9)
Crieff (A85)
Perth
A912
A912

(A9)

A912
Perth
Stirling
Pitlochry
(A9)
LanesLanesLanesLanes LanesLanesLanesLanes
3 miles, 2 lanes 3 miles, 2 lanes
9 Bridge of Earn
Aberargie
A912
A912 A912 Bridge of Earn
Aberargie
A912
LanesLanesLanesLanes LanesLanesLanesLanes
9 miles, 2 lanes  
8 Cupar
St Andrews
A91
(A91)
LanesLanesLanesLanes
3 miles, 2 lanes 11 miles, 2 lanes
7 A91 A911 Stirling
A91
Milnathort
A911
LanesLanesLanesLanes
  1 mile, 2 lanes
6 Kinross
Milnathort
A977
Services Kinross
A977 A977 Kinross
Crook of Devon
A977
Services Kinross
LanesLanesLanesLanes LanesLanesLanesLanes
3 miles, 2 lanes 3 miles, 2 lanes
5 Cleish
Crook of Devon
B9097
B9097 B9097 Cleish
Ballingry
B9097
LanesLanesLanesLanes LanesLanesLanesLanes
3 miles, 2 lanes 3 miles, 2 lanes
4 Kelty
Ballingry
A909
B914 A909 Kelty
Lochgelly
A909
LanesLanesLanesLanes LanesLanesLanesLanes
4 miles, 2 lanes 4 miles, 2 lanes
3 Dunfermline
A92
A92 A92 Dunfermline
Kirkcaldy
Glenrothes
A92
LanesLanesLanesLanes LanesLanesLanesLanes
0.5 miles, 2 lanes  
2A Kirkcaldy
Glenrothes
A92
(A92)
LanesLanesLanesLanes
2.5 miles, 2 lanes 3 miles, 2 lanes
2 Dunfermline
Rosyth
A823(M) Link
A823(M) Dunfermline
Rosyth
A823(M) Link
LanesLanesLanesLanes LanesLanesLanesLanes
0.5 miles, 2 lanes 0.5 miles, 2 lanes
1 Kincardine
A985
Dalgety Bay
Inverkeithing
A921
A985





A90
A921




Inverkeithing
A921
Kincardine
Glasgow
A985
LanesLanesLanesLanes Signs LanesLanesLanesLanes Signs
   
Route follows A90 for 4.3 miles
M90 Queensferry Crossing due to open August 2017
 
A90

A90
Edinburgh
A90
LanesLanesLanesLanesLanes Signs LanesLanesLanesLanesLanes Signs
2 miles, 2 lanes 2 miles, 2 lanes
M9 J1A N/A M9









SOUTH
M9
(M8)
(A8)
(A89)





Airport Airport (A8)
Broxburn (A89)
Glasgow
Edinburgh
(M8) Link
Kincardine
Stirling
M9 Link
LanesLanesLanesLanes LanesLanesLanesLanes
Routes

Picture credits

With thanks to Michael Clarkson, Jon Davey and Liam Philliban for information on this page.