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Trams trial

Last week NCE reported HM Railway Inspectorate was looking for approvals inspectors. But what do they do? Richard Thompson spent a day with one on Croydon's new tram system.

Britain's dithering over whether or not to sign up to the single currency is akin to Nero's fiddling while Rome burned. Because whether we like it or not the country is becoming more European every day.

Take Croydon. Its 1950s planned town centre is about to gain a distinctly Teutonic tram system. Graceful red and white trams, identical to those used in Cologne, are already silently gliding through its crowded pedestrian precincts and leafy outskirts. The town has the feel of a modern European business centre.

Unfortunately Croydon's residents are not so European. Britain's road users - particularly its notoriously anarchic pedestrians - have no idea how to behave around trams.

This is the key issue for railways inspector David Thornton. Thornton has to be convinced that Croydon's £200M Tramlink is completely safe before he will grant it the HM Railways Inspectorate approval it requires before it can open on 4 November.

'The central issue I am looking at is how the trams interact with other vehicles and pedestrians,' says Thornton. 'Tram design is all about trying to foresee what the motorist or pedestrian might do and try to mitigate against it. Several generations in this country have never seen a tram. So you can't just lift in Continental practice.'

A key feature of tramway design is that trams, unlike trains, operate by line of sight. This means the driver has to be able to see and predict what is going on. In that respect a tram has to be considered as another highway vehicle like a car.

'Only it can't swerve,' says Thornton. 'It can stop very quickly but you don't want that because the passengers inside will be thrown about.'

One example of how the designers have tried to make life easier for the driver is at East Croydon station. It will be the busiest stop on the Tramlink system with trams passing through every two minutes during rush hour. The new tram lines sit between the railway station exit and the old bus stop location.

'We had to consider that people are used to coming straight out of the station to bus stops,' Thornton explains. 'So I am happy to see the designers have put a barrier at the back of the tram stop with only two crossing points. This allows the driver to know and predict where pedestrians will try to cross.'

HMRI has worked with Tramlink client Croydon Tramtrack, engineer Gibb and the Amey/ McAlpine joint venture contractor from the beginning of the project to ensure it meets all the safety requirements.

The trams already running serve a number of purposes. Firstly they allow Thornton to assess how the tram interacts with other traffic and pedestrians. Second it allows the operator First Group to train its drivers and commission its sophisticated control room. It also allowed the joint venture to assess whether the network's operating systems function properly. But most important of all, it allows Croydon residents to get used to seeing the trams on the streets.

'We did the initial runs to check that the signalling system was working satisfactorily,' says joint venture deputy project manager Stuart Bawden. 'We then kept them running because HMRI want us to get people used to the idea of trams running, particularly on issues like parking. Parking on the tramway is illegal.'

Tramlink has been able to draw on the experiences of earlier UK tram schemes in Sheffield and Manchester. An important safety lesson learned from Sheffield has been the use of skid resistant road surfacing around the rails.

At Croydon the rail base is topped with modified bitumen with a high PSV stone filler similar to that used on bridge joints on highways to provide skid resistance.

The ability to stop safely on steep gradients is another key issue. On the first few test runs it was found the tram could not stop on the pedestrianised Crown Hill without using the emergency magnetic track brakes. Its 9% gradient is steepest part of the system. The reason was found to be debris on the tracks causing the wheels to skid. For the trams to stop using the gradual service brake, they have to slow down to 10km/h before they start the hill.

Sand bags have been used to simulate passenger loading conditions and washing up liquid has been used on the tracks to simulate wet and icy conditions. Thornton even went to Vienna, where Bombardier manufactures the trams, to witness braking trials.

'The trams are approved for running now,' says Thornton. 'We had to be satisfied the tram can stop on a steep gradient using the service brake. It is not acceptable for the tram to stop suddenly.'

One issue that has dismayed Croydon residents has been the appearance of large H-section stanchions on the town's pavements to carry the overhead power lines (NCE 25 March). This also raised an issue with HMRI.

'The columns add to the clutter on the pavement,' says Thornton. 'This can obscure visibility allowing people to step into the path of a tram without giving the driver any warning.'

Joint venture chief engineer Graeme Cunningham explains that power lines have been suspended from buildings where possible but many have not been suitable.

Thornton is keen to stress that it is not the inspector's job to inspect every nut and bolt. 'Our main function is looking at safety aspects and sniffing out possible problems. To some extent it is sampling,' he says. 'But a lot of it is experience. The inspector develops a nose.'

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