Clyde Tunnel

Clyde Tunnel

The south portal of the Clyde Tunnel at Linthouse
Overview
Official name	Clyde Tunnel
Location	River Clyde,LinthouseandWhiteinchinGlasgow
Coordinates	55.86867°N 4.33115°W/55.86867; -4.33115
Route	part ofA739
Operation
Opened	3 July 1963
Operator	Glasgow City Council
Traffic	65,000
Toll	Free
Technical
Design engineer	Sir Alan Muir WoodofHalcrow
Length	762 m (2,500 ft) (northbound and southbound)
No.oflanes	4
Tunnel clearance	17 ft 6 in (5.3 m)

North entrance to one of the cyclist and pedestrian tunnels (east)

TheClyde Tunnelis a crossing beneath theRiver ClydeinGlasgow,Scotlandfor road traffic, cyclists and pedestrians. Two paralleltunneltubes connect the districts ofWhiteinchto the north andGovanto the south in the west of the city.

History

Efforts to improve the transport infrastructure of Glasgow post-World War IIwere hit by the problem of crossing the Clyde. Downstream of Jamaica Street in thecity centre,it was perceived to be impossible to build abridgedue to the prevalence ofshipping.The solution — to build a tunnel beneath the river — was not a new one, with theHarbour TunnelatFinniestonhaving been built in the 1890s. However, the Clyde Tunnel project was to be built in the boom of the car era and would be a much larger project. It was given the green light in 1948 but financial difficulties prevented work from beginning until 1957.

Construction

Construction began in 1957, withtunnelling shields,based onMarc Isambard Brunel's design used for theThames Tunnela century earlier, used to dig the two tunnels.The tunnels were cut perfectly circular with the road deck sitting a third of the way up.Under each road deck is the pedestrian/cycle tunnel and ventilation ducts. 16minersoperated the shield working shifts in acompressed airenvironment to ensure that the rock and the river above did not collapse into the tunneling area. The digging itself would be done only with great difficulty due to thegeologyof the area, hard rock sitting under a softsiltlayer beneath the river.

The techniques for decompression after a period of working in a high pressure atmosphere had not been perfected at this time and – also owing to the prevalence of workers refusing to go through the decompression sequence given the length of time required (around an hour) – there were a number of cases ofdecompression sicknessdiagnosed as a result, resulting in two fatalities.Work on the tunnel was halted for a time after an explosion when compressed air escaped through the tunnel lining into the river, flushing outward in a fountain.

The first completed tunnel tube, for northbound traffic, was eventually opened byElizabeth IIon 3 July 1963,with the southbound tunnel opening in March 1964. The total cost of the project was£10 million. (equivalent to £304,530,000 in 2023).By this time, the migration of port facilities downstream to the deeper waters of theFirth of Clydeand improvements inengineeringtechnology had allowed the consideration of bridges downstream of the city centre, namely theKingston Bridgeand, much further downstream than the Tunnel, theErskine Bridge.

The tunnels

The road tunnels are each 762 metres (2,500 feet) long with agradientapproaching 6% or 1:16. The width of the river at this point is 123 metres (404 ft). Each road tunnel carries two lanes of traffic as part of the A739 road, and are completely separate except for a very small crossover passage between the road tunnels at thenadir(barely large enough for a single pedestrian). They are monitored and controlled from the two Portal towers, one at each end of the tunnel, whereCCTVmonitors the entirety of the tunnel. Beneath the road tunnel decks run foot and cycle tunnels; and below those, the tunnels' services.

Pedestrian and cycle tunnels

Both tunnels are open to pedestrians in both directions. The eastern tunnel is open to cyclists going southbound, and the western tunnel to cyclists going northbound. In 2008,CCTVsecure entry systems were installed at the portals of these tunnels in order to reduce crime andanti-social behaviourin the tunnels.

Repair work

The estimate for traffic levels in the tunnel was between 9,000 and 13,000 vehicles per day during construction; on the first day of opening, 22,000 vehicles used the tunnel. Current estimates for traffic levels are around 65,000 vehicles per day. These unanticipated high volumes of traffic have increased the wear rate for the tunnel, causing it to close repeatedly for repair and renovation work, which has disrupted traffic in the area for over a decade, and has arguably led to the increase in traffic causing similar problems on the Kingston Bridge.

The more recent repairs, costing as much as the initial outlay for construction, involved installing a second, modern, fireproof layer, enabling the tunnel to meet European safety standards after St Gotthard andMont Blanc tunnel fires,along with new air extraction systems and newlighting.Work began in March 2005 and was scheduled to last until at least April 2006, with one of the tunnels closed during off-peak hours (19:00 to 07:00 daily). However, problems that were encountered meant the work was only completed in 2010.

The roadworks coincided with the "Hold Your Breath" project which aimed to add anartisticexperience to travel through the tunnel. The pedestrian tunnel also had its years ofgraffitiremoved as part of a beautification project, but it was often redone soon after being removed.

Breath holding

A popular game amongst local children, and some adults, is attempting to hold one's breath for the duration of the journey by motorized vehicle through the Clyde Tunnel. This is possible due to the short length of the tunnel – a car travelling at the 30 mph (50 km/h) limit takes 57 seconds to pass through. Success is hampered by snarl-ups (particularly at the interchange on the north end) slowing traffic. The breath-holding game was the subject of Scottish artistRoderick Buchanan'svideoGobstopper,for which he won theBeck's Futuresart prize in 2000.

External links

Media related toClyde Tunnelat Wikimedia Commons

• Glasgow Motorway Archive - Clyde Tunnel and Approaches
• Clyde Tunnel pageon the Glasgow City Council website
• TheHold Your Breathproject