Tamar Bridge 60th Birthday
There’s been a lot of talk in the regional news over the past few days about the Tamar Bridge and it’s 60th anniversary. Well, here’s the article I wrote for the Western Morning News a decade ago when the famous bridge had knocked up half a century…
We tend to take a lot in life for granted, even impressive man-made structures eventually pale into the background – but imagine if something important like a big bridge suddenly disappeared…
The Tamar Bridge, for example, has being doing sterling work for 50 long years this month – yet most of us give it hardly a thought and even moan about the occasional traffic queue we may encounter on the vital Devon-Cornwall link.
Photographer Steve Haywood gets a shot of engineer Richard Cole high up on the Tamar Bridge
But can you imagine what the queues for the Torpoint ferries would be like if there was no bridge? Can you envisage what it would be like to drive all the way to the next nearest Tamar crossing at Gunnislake along narrow roads?
Not likely… Which is why all West Country dwellers should be celebrating the bridge’s half-century anniversary later this month.
It was on October 24 1961 that the late Queen Mother officially opened the big span which, at the time, was the longest suspension bridge in the UK.
Since then countless millions have made the crossing. To give some idea of the numbers, present monthly traffic averages at around 650,000 each way – which works out at around 16 million crossings a year.
Or to put it another way - it’s estimated that of the longest-serving toll collectors working in the booths located on the Devon bank has personally taken 10 million tolls in the last 20 years.
Not that any of these staggering statistics regarding tolls is making anyone rich – the Tamar Bridge is publicly owned and all monies collected are spent on maintenance, upkeep and the occasional improvement.
Most readers will know that a major example of the latter was carried out in 2002 when the bridge was strengthened and widened to carry five lanes rather than three.
Far from taking the bridge for granted, we decided to take a long hard look at the vital link in the run-up to the 50th anniversary celebrations which will culminate in a special ceremony on 6 December when HRH the Princess Royal will revisit the structure having reopened it after the widening work.
The first thing to say about our visit is that climbing to the top of the bridge’s 200-foot towers is a breathtaking thing to do – both in the number of ladder steps climbed and in terms of the amazing views you get at the top.
But before we went aloft we met David List, who is general manager of both the Tamar Bridge and Torpoint Ferries – a combined job which is the only one of its kind in the UK.
“There’d been proposals for a bridge since the 1920s,” said Mr List when we met in the Tamar crossing offices situated on the Devon bank next to the bridge. “After the War talks started again and the two authorities either side of the river - Cornwall County Council and Plymouth City Council - promoted the idea of a bridge. They lobbied government without success, but by 1955 they were saying: ‘Right we’ll go our own way and build it ourselves’.
“The first process was to get the Tamar Bridge Act through parliament because you need more than planning permission to put a toll bridge up. Obviously you’ve got to have the landfall each side, and the approaches - you’ve got to cross the river which is invariably owned by somebody - in this case the Duchy of Cornwall and we actually pay them a small rent for using the airspace above - and then you need power to take money off people because it’s a public highway.
“So what you need is primary legislation,” Mr List went on. “The Tamar Bridge Act got Royal Assent in 1957. It is a very carefully worded piece of legislation because it is a public facility - it controls us and what we do. We can’t take loads of money off people then use it for Plymouth schools, or Cornwall social services or whatever… That money can only be used to operate maintain and improve the bridge and the ferry.
“Because the Torpoint Ferry was then in Cornish hands the decision was made to combine management of the ferries and the bridge - both are in public ownership so it makes sense that the tolls, traffic management and everything are kept in one place.
“Tragically, seven people died in building the bridge. There was a boating accident and five lives were lost in that - and two other people died on the project. In those days it wasn’t that unusual I’m afraid. Today it would be very tragic and unusual for someone to die on such a project. But if you look at the photos of the construction, people were just sitting on beams with no harnesses or anything.
“The bridge itself is a steel structure - there’s a truss which stiffens the section that carries the vehicle deck. A suspension bridge works on a washing line principle - the suspension cables are the washing line, the deck and road is like the washing - and the hangers down from the cables are like the pegs.
“A rope suspension bridge wobbles - you have to stiffen your bridge for traffic - and that’s what the truss does. It spreads the load so one peg isn’t taking all the weight - and also makes it stiff enough. This bridge has a relatively deep truss.
“I think all trainee engineers have seen the video of the Tacoma Bridge which goes into a sort of galloping resonance in high winds,” said Mr List referring to the infamous events which overtook the span in Washington State. “There is a view that our truss is particularly deep and stiff as a reaction to that incident - so ours is not the most slender suspension bridge.
“This is an exposed structure but because our span is relatively short high winds are not a big issue for us,” he added. “Also our prevailing wind is the south westerly and we’ve got a nice railway bridge here which baffles the worst of that.”
Looking back over the 50 year life of the bridge Mr List told me: “To begin with the crossing wasn’t cheap. Four shillings and sixpence - which is 22.5 pence today - that was a hell of a lot of money in 1961. The crossing is only 75 pence now for the discounted toll.”
He also talked about the strengthening and widening work: “Europe said all member states had to look at major highways and if there were any structures they had to handle European standard traffic into the future which includes vehicles up to 40 tonnes.
“On structures and highways it’s the big trucks that do all the damage. The cumulative damage can be to the power of four of the weight of the axles - so 10 times the axle weight – that’s 10,000 times the effect on the steel. One large truck can do the damage of 10,000 car axles.
“When an assessment was done of our bridge there was some good news - the towers and main cables were in good shape - but the problem was the deck was relatively weak and some areas of the truss needed strengthening. So if you’ve got to change the deck where all the traffic goes you’ve got a big problem - how do we take the traffic off there to do the improvements? So that’s why the cantilevers were added - the initial thought was that they would be the diversion - but they subsequently decided it wouldn’t cost much more to make those permanent and add capacity for good.
“It’s the first time a bridge has been strengthened and widened and open to the traffic at the same time. We did win a world first for that and got a lot of accolades like the British Construction Industry Award for that year.
“When I first came here in 1997 you regularly had traffic queuing back beyond the tunnel,” said Mr List. “Recently we’ve had congestion again with the resurfacing because we’re down to the old number of traffic lanes - just three - and that’s what happens. We are only resurfacing the Plymouth side span - this is where the heavy goods vehicles are approaching the toll plaza and the slower they go the more damage they do.”
Mr List also talked about the payment systems which had been used: “We had prepaid vouchers from the beginning - we only phased that out in 2007 - it’s always been a case of prepaying gets a better deal. Here’s it’s been up to 75 per cent discount over the years - usually around 50 per cent - which is the highest anyone gives in the country.
“We are trying to get people through the booths quickly and a voucher is better for that than money. So front-up with the toll in advance and you get a cheaper crossing.
“When we strengthened and widened the bridge we added capacity for traffic, but the toll booths became the bottleneck so that was the catalyst for the new TamarTag electronic toll system. You attach a transponder to the vehicle in the right place so it can be read easily. The roadside equipment talks to it - checks its ID with the records in the office - is it the right bridge for instance or is it a Dartford tag? The barrier goes up, vehicle departs and the tag is told, ‘I’ve taken a toll off you’. If you get to a certain threshold there will be a warning saying low balance. People can buy on the internet or over the phone.
“The limit we were hitting with manual tolling was about 500 vehicles an hour - with the tag systems we can get 700 to 800 an hour. In the morning rush hour there will be typically four or five cars waiting for each toll booth - every morning without fail it used to be back across the bridge and often into the tunnel. We now have over 84,000 tags out there which puts us ahead of all other operators except Dartford.
“The limit we were hitting with manual tolling was about 500 vehicles an hour - with the tag systems we can get 700 to 800 an hour. In the morning rush hour there will be usually four cars waiting for each toll booth - every morning without fail it used to be back into the tunnel.
“The bridge should be here for well over another century because at the time of strengthening and widening we had an estimated 120 year life. The Brunel Bridge has outlasted that and it was built without the same control standards we have,” said Mr List talking of the bridge’s future.
“Our paint isn’t perfect and we have to do a full re-coat of the bridge in the next five years which is going to be expensive. It’s the kind of work the tolls are paying for.”
At this point we were joined by Mike Pender, one of two bridge operations managers, who’s worked on the bridge for over 25 years – and it is a poignant fact that Mr Pender’s father was one of the seven people who died during the building of the big span…
“I’ve thought about my father working here – it is very poignant, but me being here is a pure coincidence,” he said, explaining that he literally walked into the job while working for a security firm after police had uncovered a massive fraud operation concerning the tolls.
“I’m basically in charge of the day to day running of the bridge,” said Mr Pender. “We’ve got six toll booths and seven lanes of traffic. In the main bridge control room we’ve always got a duty supervisor and they are helped in the busier period by a control room assistant. The control room is in use 24 hours a day so we need a team of five supervisors and three assistants to cover. We have contracted toll collection staff – they are currently provided by OCS.
“I was here in 1986 when they were constructing the Saltash Tunnel and that made a big difference,” added Mr Pender who has put together a scrap book containing press clippings about the bridge.
“In the old days there were only two cameras - it was just a case of controlling the three lanes of traffic with a dial switch. Now it’s a lot more complicated,” he said, showing us the high-tech control room which overlooks the bridge.
And it was onto the bridge we went next in the company of engineering manager Richard Cole. It was he who fitted photographer Steve Hayward and me with harnesses so we could climb the tower on the Plymouth side.
“We’re going up 75 metres – that’s over 200 feet from the water level. We come up here regularly to inspect the structure,” he said as we climbed a series of ladders inside the tower. “The cables are important - we regularly inspect them and also the hangers which we and contractors abseil down in a bosun’s chair.
“You get used to it,” said Mr Cole as we looked down into the watery abyss. “The main cable is about a foot wide and it has anti-slip paint which is important - and we clip on so we’ve always got two points of contact. It gets pretty windy. It does get to a state where it gets uncomfortable - you will feel the tower is moving – so we have maximum wind speeds for that type of work.”
It occasionally felt like the tower moving as large trucks passed by below – and nothing, not even a royal edict, would persuade me to step out onto the narrow cables which Mr Cole has to inspect on a regular basis.
But what I could see from the lofty vantage point is that the Tamar Bridge is a very impressive structure indeed – and never again will I pass over it and take a single nut or bolt of it for granted…
Tamar Bridge Fact File
Main span is 335 metres between the two towers.
The side spans between towers and the land are 114 metres long making the bridge a total of 642 metres long.
The towers are constructed from reinforced concrete rather than steel and rise from the caisson foundations to a height of 73 metres.
The tower walls are 0.6 metres thick and taper inwards as they rise. The caisson foundations were founded on rock at an average depth of 13 metres below ordnance datum. The main road deck is suspended at approximately the mid-height of the towers, 37m.
The two main cables are each 350mm in diameter and each comprises 31 galvanised coil wire ropes 65mm in diameter. The locked coil ropes are each made from approximately 120 individual wires.
Each of the 31 ropes weighs 14 tonnes and is approximately 670 metres in length.
The coil ropes are connected to steel rods which are embedded in the concrete anchorages 16 metres into the rock.
The total weight of the two main cables is approximately 850 tonnes.
The roadway was suspended from the main cables using 120 separate locked coil wire hanger ropes, 60 to each cable and spaced at 9.1 metre centres.
The road deck is supported by a steel stiffening truss constructed in sections each weighing approximately 80 tonnes, with a total weight approaching 3000 tonnes.
The recent strengthening and widening work added two new cantilever lanes, 18 additional wire ropes and additional steel strengthening plates.
The original suspended weight of the Tamar Bridge was 7900 tonnes. The current structure now weighs 7925 tonnes despite the addition of new lanes, cables and strengthening.
In the year 2010 approximately 16 million vehicles crossed the bridge.
