A jam in London's Trafalgar Square Connie Ma/Flickr

The U.K. capital was a global leader in taming congestion 13 years ago. But the traffic has come back, with a vengeance.

In 2003, the city of London made a bold move in an effort to tame traffic: It instituted a congestion charge, making motorists pay a fee in order to drive into the city core. The law was the first of its kind in a major city, and similar schemes were later adopted in Stockholm, Milan, and other cities.

Today, 13 years later, the U.K. capital is drowning in vehicles: London has the worst road delays in Europe. What happened?

Several things, say transportation experts—and not all of them are bad. In a sense, London’s snarled streets are in part a reflection of its roaring success. It may also be a harbinger of what’s coming for many other cities.  

The positive spin on this is that London is now in a great position to provide a blueprint for better managing the future of urban congestion everywhere. But first, let’s take a closer look at what’s going wrong.

The Limits of Congestion Charging

London cars may now be moving “slower than a horse and cart” but that doesn’t necessarily mean the congestion charge was a failure. When introduced, it was designed largely to slash the number of private cars driving in to central London. In this, it has proved very successful. As the Financial Times reports, private car use has indeed dropped off sharply.

The problem is that the space vacated by those private cars has since been filled up (and then some) by other vehicles—specifically, private-hire cabs and online shopping delivery vans from the likes of Uber and Amazon. The on-demand economy is choking the city.

They weren’t a major factor in London traffic 13 years ago, and they’re are not deterred by the current £11.50 ($14) daily charge to drive into the zone. Because they count as public transit, Ubers don’t even pay the fee.

These new congestion-charge-immune vehicles motor into a city whose road space has shrunk, thanks to lane closures caused by major construction work and new cycle highways. Add London’s galloping population growth, which surpassed its previous peak of 8.6 million in 2015 and could reach 10 million by 2030, and you have a complex knot of problems that will take some unpicking. But how?

Install Better Traffic Systems

Transport for London, the city’s overseeing transit body, is developing better traffic signaling and predictive modeling to help control inner-London congestion, says Garrett Emmerson, TfL’s COO of Surface Transport. Two-thirds of London’s 6,000 traffic lights now use the SCOOT adaptive control system. This changes each set of lights’ signaling patterns to respond to demand—not working independently of each other but connected up to a system managing flow through junctions and key corridors.

This already-common system will soon be linked up to bus services, a major factor in a city that hosts 6.5 million journeys by bus passengers daily (compared to 10 million by private car). Data relayed by the SCOOT system could, for example, signal to bus drivers to give up their normal priority at traffic lights, if doing so would increase traffic flow. The sheer frequency of London’s buses still makes this challenging. “Joining up the traffic light and bus systems is harder in London, because our buses run so frequently that they don't run to timetables,” Emmerson says. “They run to headways [i.e. ensuring a fixed distance between each bus], so that there is an even flow of buses down the route. That makes it much more complicated for the traffic signal systems to understand what's happening with the buses, but we're now getting there.”

TfL is also trying to smooth flows by giving more information to private drivers. Over 1.5 million people (equivalent to a quarter of London’s drivers) now follow the TfL Twitter account, for example, which dispenses traffic alerts and other useful information. A possible next step Emerson and his colleagues are exploring is relaying traffic information to motorists via screens on the back of buses, which can display traffic advice specifically relevant to the bus’ GPS location.

These measures that are already underway could help grease the wheels of London’s road system. But to actually resolve rather than just ease the problem will probably take something more drastic.

Retractable bollards in a street in Barcelona. (Eric Fischer/Flickr)

Restrict Car Access Even Further

One more radical approach would be to further cut the amount of road space cars can use. TfL has already done this to an extent by creating new segregated cycle superhighways” carved from the road network, much to the consternation of certain Londoners. On this issue Emerson makes another important point: Bike lanes being used at full capacity actually can actually channel more people than motor-vehicles-only roads. “The cycle superhighways have taken out some road capacity [for motor vehicles], but there's more capacity for actual people,” he says. “The number of cyclists on these routes has grown over 50 percent in just 6 months, which means we're now getting more people down those corridors every hour than we ever did before.”

While building more bike infrastructure should lure more drivers out of their private cars, it would be less effective on easing van and private-hire cab congestion on the road space that remains. To do that, you might need to entirely restrict car access to certain areas, a strategy suggested by Ashok Sinha of the London Cycling Campaign.

“One of the biggest barriers to cycling is fear of collisions—that's addressed not just by cycling infrastructure but by reducing traffic volumes and speed in places where most traffic really isn't necessary, such as residential areas,” Sinha says. “You can ask yourself: ‘What is the purpose of most traffic going through a particular area?’ In a lot of cases it isn't necessary for traffic to go through narrow streets. Instead, motor vehicles could be re-routed through a coarser grid of higher-volume roads, which would leave the smaller roads within them much calmer. This would mean more people could walk and cycle through them, already common practice in the Netherlands, where most cycling is done on roads or paths that aren't specifically separate.”

Such a system could be introduced in a more sophisticated way than by simply blocking off roads, Sinha notes. Street plans could be reshaped so that it was possible to drive in and out of an area, but not to drive through it. Bollards can also be retractable, sinking into the ground when emergency access was required or during quieter periods of the day.

Boston’s Big Dig may have inspired ex-mayor Boris Johnson to construct major road tunnels under London. (John Niedermeyer/Flickr)

Dig, Baby, Dig

Another way to get cars off surface streets—build sub-surface ones. Burying the highway can be a wildly expensive traffic solution, as Boston demonstrated with its infamous Big Dig, but several similar projects are being tried in European cities. Stockholm is currently constructing a huge subterranean bypass that, when completed in roughly ten years’ time, will channel through-traffic across the city away from the existing surface road system. London’s former Mayor Johnson proposed a similar solution for the UK capital in February.

The plan has some attractions. If existing arterial roads were buried, the areas around them would be far less polluted, while burying car lanes could also free up road space at surface level for building more homes. The idea nonetheless has some obvious drawbacks, encapsulated by a speech made by Darren Johnson, a Green Party representative addressing the London Assembly last year. “Sticking traffic in underground tunnels is counterproductive,” he said. “It will do nothing to get cars off the roads. If these plans go ahead, we will waste the money that we need to be spending on encouraging public transport, cycling, and walking.”

Given the huge expense of burying roads (and the departure from London politics of the plan’s main advocate, ex-Mayor Johnson) it seems unlikely that this direction will be adopted in the near future.

Create “Bus Gateways”

In London, it’s not solely cars, truck and vans that cause congestion. Buses are so numerous along key corridors such as Oxford Street that they form bus-jams that belch out Beijing-level pollution. Rethinking routes could ease these jams by reducing the number of larger buses driving empty.

“At the moment you have a situation where double-decker buses are coming into Central London, rapidly depositing passengers before traveling along the rest of their route, often with few people left on them,” says Ashok Sinha. “TfL are currently looking at the possibility of creating several ‘bus gateways’ around the edge of Central London, where larger buses could arrive, drop their passengers, and turn back out of the city. Passengers could then transfer onto smaller hopper-style electric buses to continue their journey, with the larger buses essentially acting as shuttles.”

Clearly this is a system that would need careful management if the gateways themselves weren’t to become bottlenecks. But while passengers would need time to change buses, they could potentially earn this time back if the smaller electric vehicles can make better progress.

A road shield making an entrance to London’s congestion charge zone. (Mariordo59/Flickr)

Introduce Surge Pricing

Just because London’s congestion charge doesn’t deter Amazon and Uber doesn’t mean that the entire concept of congestion pricing should be jettisoned. David Begg, professor of Sustainable Transport at Plymouth University and publisher of Transport Times, argues that the system needs updating, extending and streamlining. In fact, the city could borrow a page from the Uber playbook and introduce congestion surge pricing. Such a system would raise or lower congestion charge fees depending on the hour of the day. This would provide a genuine disincentive to driving at busy times rather than just a skim-off tax that deters only the less wealthy.

“We need to move towards a dynamic charge that reflects the level of congestion,” Begg says. “It's no different from the way we pay for other utilities—you get a reduction for using electricity during the night rather than at peak hours. You can get off-peak prices on trains. The market and price mechanism is working for other utilities, just not for roads.”

Reroute Delivery Vans

London’s problem with online delivery vans isn’t just that they are too many of them. It’s where they are: delivering to people’s workplaces in the city during the day rather than to their homes in the evening. This needs to change, says Begg. “We have to encourage delivery vehicles to make more evening drops-off to homes, when people want the parcels to be delivered, rather than during the day or the middle of the rush hour. It costs more for delivery companies to deliver in the rush hour because they're traveling slower, they're using more fuel, more drivers time. You would have thought that congestion itself would have given an economic incentive for the Amazons of this world to deliver in the evening, but currently it's not working.”

Another way of diverting delivery vans from the city core could be to provide more local depots for click-and-collect shopping—places where shoppers can pick up goods by providing a customer code.

Hold Out for Autonomous Vehicles

In the current discussion of urban transit and congestion, autonomous vehicles inevitably show up as the future fix-all. There’s a vigorous debate raging in transit-geek circles about whether AVs will relieve or exacerbate current traffic trends. But there should be at least one clear benefit: High-speed highways filled exclusively with driverless cars should at least be less prone to human-error-caused jams. That should help ease delays for suburban commuters heading into the city.

“Humans tend to drive at different speeds relative to the other,” says Carnegie Mellon University’s Raj Rajkumar, an expert in vehicular information technology. “We also tend to at first underreact to things around us because we are distracted, then overreact to compensate for the delay. That cycle ultimately causes a cascading effect. First, one person cuts up another vehicle on the road, causing them to slow down. The driver behind then slows down too much until eventually a vehicle comes to a stop and a jam starts to form.”

This popular explainer video from CGP Grey illustrates the process.

As Rajkumar says, a platooned formation of autonomous vehicles could break this jamming cycle of under- and overreaction to create a smoother flow. “If all the cars that end up in these jams were self-driving, they would be constantly reacting appropriately. The net result of that is that they could all be moving forward at a collectively uniform speed and therefore the throughput of existing roads would go up.”

Self-driving also holds promise for fixed-route vehicles such as buses and vans—major sources of London congestion—since they’ll probably be among the first vehicles to go fully autonomous. But when that happens remains an open question. Despite headline-grabbing stunts like Uber’s recent autonomous beer delivery and Tesla’s claim that all its new vehicles are fully rigged for self-driving, by Rajkumar’s estimations AV technology won’t be fully mature for another ten years, and it could be 40 years until they truly own the roads. In the long interim, autonomous vehicles will need navigate among and around us imperfect humans, so their ability to dramatically reduce congestion will be limited.

Let Congestion Itself Produce a Modal Shift

Could London’s traffic get so bad that drivers simply give up and try to get around some other way? David Begg does not advocate this as an option (nor does TfL). But he does point out that, if action is not taken, this problem may essentially solve itself: Simply staying home will become London’s unofficial default means of reducing pressure from drivers. This white-flag strategy could have some benefits: According to the London Cycling Campaign’s research, 25 percent of Londoners would like to cycle more than they do. Making the driving experience more miserable is one way to encourage more of them to switch over.

“The way we run our road system is the last remnant of the Stalinist state,” Begg says. “We ration demand by queueing. We can do that, and accept that there's not going to be any proper road pricing system, but what will happen is congestion will be the regulator.”

Letting congestion essentially flourish unchecked this way would be likely to create political backlash from driver/voters, a disincentive to commercial deliveries, dangerous problems for emergency access, and no drop in air pollution. As such, it’s hardly tempting. But it could be the future London is lumbering towards anyway unless real changes are made, warns Begg.

“If we go down that road, we just have to say, ‘We've not got a solution for congestion. It's going to get progressively worse and traffic will be at walking speeds.’ If we do that, we have to collectively accept it. Alternatively, we can take radical action.”

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