The Forth Bridges

Main span: 3,300 ft.
Side spans: 1,340 ft.
North viaduct: 842 ft.
South viaduct: 1,437 ft.
Total length: 1½ m.
Height of towers: 512 ft.
Clearance: 150 ft.
Cables: 7,400 tons
Towers: 5,200 tons
Truss & deck: 16,000 tons
Truss depth: 27½ ft.
Concrete: 150,000 cu.yds.
Approach road (North): 4½ miles
Approach road (South): 4½ miles
30 minor structures
Dual 24 ft. carriageways

Central spans: each 1,710 ft.
Steel structure: 5,350 ft.
North viaduct: 967 ft.
South viaduct: 1,980 ft.
Total length: 1½ m.
Height of towers: 361 ft.
Rail level: 158 ft above H. W.
Granite masonry 740,000 cu.ft.
Rubble masonry 48,300 cu.yds.
Concrete: 64,300 cu.yds.
Steelwork: 54,160 tons
Rivets: 6,500,000
Largest tubular members: 12 ft. dia.
Double track railway which carries East coast main line.

The Forth Road Bridge from the viewing terrace.

At time of construction, the bridge was the longest suspension span in Europe, and the third longest in the world.

It was similar in dimensions to the ill-fated Tacoma Narrows bridge in the United States, and was one of the first long-span suspension bridges built taking into account the lessons learned from that failure.  The bridge deck truss is far more rigid than would have been expected, and wide openings in the deck allow gusts of wind to blow through with less effect.

The Forth Bridge, from the viewing terrace.

While the road bridge was built in the aftermath of the Tacoma Narrows collapse, the rail bridge was also constructed in the aftermath of disaster - the collapse of the Tay Bridge and the loss of a commuter train with 75 passengers in 1879.  [See: The Tay Bridge Disaster]  Construction of the Forth Bridge was halted immediately, and restarted, to a completely new design, in 1883. 

Until the 1990s, painting the bridge was a never-ending task, with the painters hanging contentedly in Boson's Chairs, but new 'Health and Safety' requirements mean enclosed scaffolding is now needed, and repainting will be on a longer-term schedule.

The Forth Bridge Hotel

The hotel is in the service area at the south end of the Road Bridge.

Access to the service area is from the A8000, about 100 metres east from the Echline interchange. 

Other services are elsewhere - public toilets are on the other side of the car park, alongside the Bridge administration building, and the filling station is directly alongside the A8000.

Pedestrian subway

Unknown to most motorists using the bridge, a pedestrian subway runs under the full width of the Toll Plaza.

It's well lit, clean, and graffiti free.  There's continuous closed-circuit video monitoring from the bridge control room and manned stations close to both exits, so vandals don't stand a chance.

Since the bridge opened in 1964, the small town of Queensferry has grown up the hill on both sides of the bridge, and the subway is now well used by locals walking between the two parts of the upper town.

The bridge from the SW

Picture taken from the footpath around the west side of the toll plaza, close to the west end of the subway. 

The two streetlights below are on a service road under the end of the bridge to the administration buildings on the southbound side.

The toll plaza from the bridge. 

The are four lanes of traffic on the approach to the tolls, two from the A90, out of the cutting on the left, and two down the ramp from the A8000 and A904.

After the tolls, traffic from all seven tollbooths, accelerating rapidly to 50 mph, converges into just two lanes on the bridge.  Traffic from the right has priority, but you've got to keep your wits about you for someone slower cutting in from the left.

From 1964 until about ten years ago, there were tolls in both directions, with a continuous line of reversable tollbooths right across the plaza.  To reduce queueing on the bridge itself, the southbound toll was abolished and the northbound tolls doubled,  with this line of tollbooths built about 30 ft. further back from the pinch point.

The bridge control building and the exit for  the A8000.

This view shows the bridge administration building surrounded by scaffolding and shrouded in polythene sheeting.  The building is being cleaned and a new surface finish applied.

The former southbound toll plaza now has a two lane bay/exit for bridge maintenance vehicles (and a bus stop), two lanes for the A8000 exit, and two through lanes on the A90.  

The nearest sign shows straight on for Edinburgh A90, and left exit for:

• Glasgow (M8)
• Stirling (M9)
• City Bypass (A720)
• Bo'ness (A904)
• Airport (A8)
• Kirkliston A8000

The gantry signs at the A8000 exit.

The gantry also functions as a footbridge between the tollbooths on the northbound side and the administration buildings on the southbound side.  Prior to elimination of the southbound tolls, the tollbooths stretched in a single line across the plaza, and collectors could cross in relative safety.

Note that the National Speed Limit signs on the A90 (white disk with black bar) really do mean 70 mph - the automatic 30 mph limit on all roads with streetlights doesn't apply to classified roads in Scotland.

The speed limit on the A8000 through the Echline and Ferrytoll roundabouts is 40 mph.  The remainder of the A8000 has a 60 mph limit, but traffic is usually much slower due to congestion on the two-lane road.

Another view of the toll plaza from the north

Traffic from all seven tollbooths can be seen merging into two lanes on the bridge.

This view also shows the recent expansion of the town of Queensferry, with new housing built right up beside the toll plaza, and hotels, a petrol station, and fast-food restaurants at the top of the hill beside the Echline roundabout.

The Tollbooths from the northwest.

The side turning from which the photo was taken is the service road, which leads under the bridge and back up to the administration buildings on the southbound side.  It's normally closed to traffic.

Close view of the tollbooths.

The large light signals are flashing green arrows indicating that the lane is open.  When the lane is closed, the metal gate is swung out, with red lights showing both on the gate and on the tollbooth.

All the tollbooths are manned, with payment by cash or pre-pay voucher only.  Automated collection systems are on hold until the government position on congestion charging is clarified.

Another view of the tollbooths.

The large black panels above the tollbooths are matrix displays showing the class of vehicle which has just passed through the toll - they're visible from the control room in the administration building.

Another view of the tollbooths, with the administration and hotel buildings in the background.

View north through the toll plaza towards the bridge. 

The width limit between the tollbooths is 9'6" - the leftmost booth has a wider lane for trucks, and a second lane which can be opened up for oversize traffic.  The carriageways on the bridge itself are 24' wide.

The bright retro-reflective signs show the problems of the midday sun in a Scottish winter.  The sun at noon is still only about 12 degrees above the horizon, with glare causing problems throughout daylight hours.

View north showing the toll plaza and the bridge.

This is fairly light daytime traffic, but even so there is some queueing. 

At northbound peaks, delays at the tolls can result in congestion up to five miles away.

Southbound peaks, even with no southbound tolls, still cause congestion three to four miles from the bridge.  The biggest restriction now is the A8000, which funnels more than half of the traffic from the bridge through a single lane.

A wide view of the toll plaza, showing the approach lanes from the A8000.

The large area of hatching which separates the A8000 and A90 traffic was originally grass.  It was filled in at the time the tollbooths were repositioned.

It should be noted that the mainline flow on the A90 has only three tollbooths, but traffic joining from the A8000 gets four.  A90 traffic is predominantly private cars, and with nearly five miles of dual lane carriageway available for queueing.

Traffic from the A8000 has a higher proportion of large and slow commercial vehicles, and very  limited queueing space, so this flow needs more tollbooths to keep things moving smoothly.

The hotel building.

The service area at the bridge consists of this hotel and restaurant building, bridge administration buildings, and a separate filling station.  The viewing terrace is also accessed from the car park.

The service area is accessed from the A8000, about 80 metres east from the Echline interchange.

This view is from the A8000 ramp, on the far side of the A90 dual-carriageway.

(My current main transport is the midnight blue Rover Mini 1000 parked in front of the hotel.)

Looking southeast on the A90

This view, under the Echline interchange bridges, was taken from the A8000 ramp down to the toll plaza.

The A90 dual-carriageway runs 4½ miles towards Edinburgh, with three grade separated junctions.  Westbound traffic on this stage is already slowing for the tolls as it passes under the two bridges of the Echline roundabout.

(This photo was taken just an hour after midday!)

View of the bridge from the A8000 ramp.

The 15 ft. side walkways on the bridge are open to pedestrians and cyclists, and are also used by bridge maintenance and emergency traffic. They see a lot of traffic in the summer months.

Proposals have been made to use them as bus or HOV lanes, but the weight penalty of new pedestrian/cycle lanes, plus a potential 50% increase in the total vehicle weight on the bridge, could compromise the safety margins on the suspension cables. 

The main bridge deck is in four separate sections, with wide openings between to reduce the effects of wind buffeting on the bridge structure.  There's no direct access between the sections, apart from three short crossovers between the main carriageways which were added to assist with maintenance works.

View north from the overbridge at the Echline interchange. 

The normal speed limit on the toll plaza and on the bridge is 50 mph, although this can be reduced with VMS on the bridge itself for high winds or poor visibility. 

High winds are a major problem on the bridge.  With moderate conditions, a 30 mph speed limit is imposed and high-sided vehicles double-up for the crossing. 

With more extreme conditions, the bridge is closed altogether to high-sided vehicles, and also to motorcyclists, cyclists, and pedestrians.  A 40 mile diversion route via the Kincardine Bridge is permanently signposted.