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Engineering the night tube

Night tube

The long awaited night tube in London will open in August this year, carrying passengers on the Piccadilly, Northern, Central, Jubilee and Victoria Lines every 10 minutes throughout the night on Fridays and Saturdays. Transport for London (TfL) has spoken to New Civil Engineer about the engineering behind the new service.

One of the biggest challenges, explained TfL network services director Kevin Dunning, was around the reprogramming of the signalling equipment on the different lines.

“If we couldn’t get the signalling systems changed then we wouldn’t have a night tube,” he said.

With the exception of the Piccadilly Line, he said that the trains all operated on an automatic train operation (ATO) system, meaning that the speed and the starting and stopping of the train was not controlled by the driver and therefore had to be reprogrammed with the new service. He said that in particular, the Central Line presented some of the biggest quirks.

“The Central Line would reset its management system every 24 hours and, of course, you don’t want it to reboot during the night,” said Dunning. “Therefore we had to upgrade the system to make sure that it would run itself for 48 hours solid.

“As part of this we actually had to go trackside and physically change the actual printed circuit boards. We’re talking 1990s technology as it’s one of our oldest ATO lines.”

The lines which have been chosen to open in August are five out of the seven ‘deep level’ lines on the network. This choice has been based on those which give good coverage to the whole of London rather than having any specific engineering barrier to opening them, said Dunning.

“Those lines cover a large percentage of the map, the main places that people want to get to,” he added

“Why did we not do the sub-surface lines, the Circle Line, the District Line and the Hammersmith and City? That’s all about demand really. If the demand grows for the night time economy then there’s no reason why we wouldn’t look at the sub-surface lines, but it needs to be demand driven.”

Noise and vibration of the track has also been one of the issues which the team has had to tackle. Dunning said that one of the main causes of the noise came from the contact between the rails and the wheels of the train. He said that over time, the surfaces become worn and needed to be re-ground to return them to their original profiles. In preparation for the night tube, he said that TFL had stepped up this process to ensure that it was as quiet as possible.

“Infrastructure on a network, track is a good example of that, you take the same approach wherever it is. To minimise the noise and vibration we’ve spent around £50M on grinding to make it as quiet and up to the best standard we can,” he explained

Traditionally, maintenance has been carried out primarily in night shifts from Monday to Friday. However, with the introduction of the night tube the pattern has had to be moved to Sunday to Thursday, which has meant the maintenance regime is largely unaffected by the new service.

Night tube work

Night tube work

One of the main causes of the noise came from the contact between the rails and the wheels of the train.  TfL network services director Kevin Dunning said that over time, the surfaces become worn and needed to be re-ground to return them to their original profiles. In preparation for the night tube, he said that TfL had stepped up this process to ensure that it was as quiet as possible.

Further to this, Dunning said that having carried out analysis on running the additional tube trains, the wear and tear on the system would only be increased by 1% to 2%. Therefore the impact of the new service was small.

“Considering the service we run throughout the day, seven days a week, this is really low level and the additional cost to maintenance is quite minimal,” he stated.

Looking forward to the future and the prospect of expanding the scheme, Dunning said that this was possible, however innovative solutions would need to be looked at to modernise maintenance of the assets.

“I think there’s still opportunity to run a longer service if the demand is there and we then need to think about technology to be able to do less frequent ‘boots on track’,” explained Dunning.

“We need to modernise our maintenance. We need to modernise the way we monitor our assets where we’re not having to touch them and become more risk based.

“The trains themselves and the depots aren’t really affected by it. The hard bit is the access, how do you access the stations, signalling and track to do maintenance.”

He said that this was already starting to be addressed by some of the newer signalling systems allowing maintenance to be carried out while trains were running.

“With the new signalling systems there is less track side equipment as they’re computer based. That’s a course to a modern railway where you don’t have to shut it down to do work,” said Dunning.

“For example, there are cameras fitted to the new S7 trains to allow us to get track data.”

Other considerations have also had to be taken into account around passenger safety when using the night tube. Stations which have access to both night tube and non-night tube running lines have had to be modified with the installation of around 300 new gates fitted to stop passengers straying onto the wrong lines. This, said Dunning, has had a knock-on effect on fire evacuations procedures in the stations which have had to be re-written.

“[There will be] gates that will be locked normally because you don’t want people to walk through, but are also part of a fire exit that will release in such an event,” he explained.

 

 

 

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