Fri. Jul 1st, 2022


London has the oldest underground railway in the world, and on May 24th, it will welcome its newest addition to the family. Crossrail is the realization of a dream first mooted in 1941, but one that would only start being built in 2009. It is one of the biggest infrastructure projects in the western world, arriving several years late and several more billion pounds over budget. But it’s hoped that this gigantic system will spur growth, relieve congestion on its Victorian-era network and remind the world of what Britain can do when it puts its mind to something. No pressure, then.

The London Underground as it exists today was borne out of a historical railway boom, with competing companies building routes to serve the city’s major economic hubs. Its many quirks are a consequence of nearly 200 years of politics, commerce, geography and geology shaping how things work. It comprises eleven lines, 272 stations and 250 miles of track, which is now under the aegis of a dedicated body, Transport for London.

Despite the wealth of transport links, many of the lines were built to serve a city far smaller than its present population. Not to mention that London is the center of gravity for far more than just the people living within its metropolitan area – it dominates much of the southeast of the country. It’s for this reason that Crossrail was given the green light, as both a way to relieve congestion on its tiny, Victorian-era tunnels, and to recognize just how broad London’s influence had become.

Crossrail Ltd.

Crossrail runs from Shenfield, a commuter suburb 35 miles northeast of London in the neighboring county of Essex, via the Great Eastern Main Line. It then runs through the city, connecting to the Great Western Main Line and then on to Reading, a large town 40 miles west of London. When fully running, it is expected to serve 200 million passengers a year, increasing London and the south east’s total rail capacity by around 10 percent in total. Crossrail is primarily an above-ground line, aside from the Central Operating Section (COS); the tunnels that run through London itself.

“It’s hard to fathom how there is space in this city to put in new stations, new infrastructure,” says Olga Konopka, Principal Delivery Engineer at Crossrail. She cited an example of how when the new Crossrail tunnels pass existing Jubilee line tunnels, the gap between them is just two meters (6.5 feet). A fleet of eight 1,000-ton Tunnel Boring Machines (TBMs) were tasked with weaving a new route through some of the most congested soil anywhere in the world. It’s one of the reasons that Crossrail’s birth hasn’t been an easy one – since you’ve got hundreds of years worth of infrastructure that you can’t touch during the construction process.

The TBMs pulled around seven million tonnes of material out of the ground, but Crossrail’s leaders said that almost all of it was re-used. For instance, around three million tonnes of soil was donated to the Royal Society for the Protection of Birds. This was used to construct a new wetland nature reserve at Wallasea Island in neighboring Essex. The rest of the clay soil was used to restore landfill, raise land and, in one instance, help build a golf course.

Image of a passenger being walked to safety along the Crossrail emergency escape route during trial running.

Luca Marino / Crossrail Ltd.

Some 26 miles of tunnels have been dug below the city, which took between May 2012 and May 2015 to complete. Konopka explained that as well as being “the biggest civil engineering project in Europe,” it also produced the largest tunnels dug for the London underground. The Central Line, for instance, has a diameter of roughly 3.5 meters (around 11.5 feet), while Crossrail tunnels are 6.2 meters (around 20 feet) wide. “Crossrail tunnels have an emergency walkway in them, which is a massive improvement to health and safety from the current infrastructure,” she said.

Konopka explained that there was some art and artistry baked into the system to help things run smoother and smarter. For instance, the gradient of the railway line gently inclines in the tunnel sections approaching a station. That way, a train slows down more efficiently since some of its forward motion is being sapped by the hill it has to climb. The situation is reversed when you pull out of a station, the track sloping almost imperceptibly downward in order to give the train a speedy departure.

It should be clear by now that Crossrail, despite the fact that it is an electric railway running under a city, is not a regular subway. It may feature on the Underground Map, and even has a line name – The Elizabeth line – but it’s not an official part of the underground itself. (Pedants beware: Crossrail denotes the project, the Elizabeth line is the thing you’ll actually be riding.) Because it connects to mainline stations at either end, and uses full-size mainline trains, it is a railway unlike anything else in the UK. In fact, the closest comparator is Paris’ Réseau Express Régional (RER), a series of lines that connect commuter suburbs to the city itself, and then moves people between stops in the city – a railway that acts like a subway when it’s in the middle of a city.

Southall platform, sign and boarding ramp.jpg

Crossrail Ltd.

One thing that was often repeated was the fact that Crossrail was a project designed to marry the very old and the very new into one seamless whole. “Farringdon was the first part of the Underground,” said Konopka, “we need[ed] to somehow marry up the old and the new, and that’s been the biggest struggle.” And making a 21st century railway run in perfect harmony with a pair of railways built in the Victorian era is one of the reasons that Crossrail’s deadline slipped from 2018 to 2022. (COVID-19, of course, was the other.)

“Conceptually, the project is brilliant,” says Colin Brown, Technical Director of the Crossrail project, but “it joins up to railways that were built in Victorian times, and that’s where your problem starts,” he said. “The Great Western was built by [Legendary engineering pioneer Isembard Kingdom] Brunel,” he explained, “and the Great Eastern wasn’t far behind it.” “The technology on those two railways has evolved over many years,” he said “but hasn’t been changed since the ‘60s or ‘70s.”

Britain’s railways, including the two main lines that Crossrail connects, use an antiquated, analog signaling system to communicate hazard warnings to drivers. This system, after a series of fatal train disasters in the ‘90s, was updated slightly to improve safety, but remains a 20th century tool. The digital replacement is ETCS (European Train Control System), which brings digital technology into the railways and promises a much safer network overall. While Crossrail was built with ETCS as standard, it also had to play nice with its analog predecessors.

Subway systems, however, use an entirely different signaling system called Communications Based Train Control (CTBC). Given the density of trains using tunnels under cities, and the need for accurate location data, CBTC is key to run services with small gaps between each train. Crossrail may not be a subway, but it will run 24 trains per hour inside the tunnels, and so needs to behave like one while it’s underground. Not to mention that CBTC is the only system that can also run the more subway-esque functions, like platform screen doors and tunnel vent interfaces.

Brown explained his dismay at the patchwork of systems and why it wouldn’t have been simpler just to pay to standardize the technology. For a variety of reasons, it wasn’t deemed feasible, and so engineers have spent years finding ways to make the old and new, analog and digital, above-ground and below-ground systems work as one cohesive whole. “You’ve [never had] a mainline train morphing into a metro train and then morphing back out again,” said Brown – at least not in the UK.

CBTC is also predominantly automatic, with drivers acting in a more supervisory role while the trains are underground.This automatic system will even operate the train when it needs to reorient itself ready for its next leg of the journey. “When it gets to Paddington,” said Pradeep Vasudev, Head of System Integration, “the driver pushes a button and then he walks from one cab to the other [at the other end of the train] while the train drives itself.” This system is also sufficiently smart that it can help find ways for the timetable to recover when a train breaks down or an incident causes a delay elsewhere on the line.

And because the system is now so much more complex, and broad, means that the timetabling systems are paramount. “For the first time, a train in Bristol [120 miles west of London] breaking down could affect a train on the Great Eastern [Main Line] in Shenfield [Crossrail’s Eastern Terminus, 35 miles northeast of London],” said Vasudev. And, of course, on the software engineering side, all of this information, and calculation, needs to be boiled down to a series of simple commands that a staffer can use to recover the service when things go awry.

One problem that Crossrail was also forced to address was the privatization of Britain’s railways in the early ‘90s. Rather than a centrally-planned and operated railway, the then Government decided to franchise each region’s railway operator. Consequently the Crossrail project had to engage with a variety of operators running different lines and find some happy harmony. “We have MTR driving, we have RFLI who owns the central section of the railway, we have London Underground, who operates a lot of the stations, we have Network Rail on either side, when we go into Heathrow, we’ve got Heathrow Express which is a different operator,” said Vasudev.

“Some of that, you’ll never get away from the fact that an operator is key, regardless of how much information the system can give you,” said Vasudev. Lee Price is one such operator, a former personal trainer and badminton coach who joined the company in 2016. Price’s story is common among new Crossrail drivers, coming from outside the train driving fraternity rather than within. This was because the project opted not to poach drivers from other underground or mainline services to avoid denting staffing levels elsewhere. (Not to mention that it helps bring the economic benefits of the system to more people, creating training and job opportunities.)

Image of an unfinished tunnel at Woolwich station.

Andrew Parish / Crossrail Ltd.

Price is now a veteran of the service, and trains other drivers, although he too isn’t yet rated for the entire route. Since it’s being used as three separate railways, it will only be after the central section is opened that drivers will be running back and forth on a regular basis.

Unlike a mainline train, or a subway, the role shifts depending on where along the route the train is. “On the East and the West, you’ll be physically driving [the train],” he said, while in the COS, “in theory, the train is automatic, but we’re there for more of a safety [role].” “Although you’re doing less, you still have to remain alert,” he added, especially in the dark tunnels that require drivers to “keep their awareness up.”

Crossrail opens to the public on May 24th, with services running between Paddington and Abbey Wood. On the day, the various arms of the service will be rebranded from TFL Rail – a placeholder name – to the Elizabeth line. 12 trains per hour will run along the line, starting at 6:30am and ending at 11:00pm each weekday, with a fuller service ramping up over time. One of the new mainline stations, Bond Street, has yet to open thanks to service delays.

Work on the project is not likely to be complete for a long while yet, but if the railway does help boost London’s fortunes, it won’t be long before eyes look forward to the next project. Crossrail 2 is a proposed line running from Broxbourne and Cheshunt in London’s northeast down to Chessington, southwest of the city. It is designed to join up routes north and south of the city, and relieve congestion on those journeys as much as Crossrail is expected to do from east to west.

Unfortunately, COVID-19 and government funding cuts have put the project on ice for the foreseeable future. But one thing that is clear, is that the expertise, the lessons learned from Crossrail’s slower-than-expected birth, are currently embedded in the team that’s just finishing their work. To let all of that experience wither on the vine would seem like a criminal waste of resources. Then again, there will be voices asking why London deserves yet another expansion of its public transport network when other major cities have nothing. As always, politics, economics, geography and geology will determine the future of the most famous tube in the world.

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