Lorries synchronised in a platoon

Smart roads and wireless communication keep the traffic flowing

Image credit: Scania

Wireless communications will help guide cars through congestion.

Traffic is building in the city as the car makes its way along the tarmac. You see an intersection around the corner highlighted on the sat nav. Before it comes into view, your vehicle slows slightly, but nowhere near enough to bring the vehicle to a halt. As you turn the corner, you see trucks and buses cross your path. But the car is not stopping.

The car seems to narrowly avoid a head-on collision as it moves into a shared lane. The oncoming vehicle darts out of the way just in time. The crossing traffic seems to stop for a moment, opening up a gap. With that, you sail through the junction. The children in the back of your car wave gleefully at the queue of vehicles left behind, stuck waiting for the old green signal to light up because their cars cannot guide themselves through.

You used to enjoy driving, even in the city, but the attraction of not waiting so long in the queue was one of the factors that convinced you to trade up to an automated car. And not just automated: it can talk to the traffic lights and the lights will talk back.

Junctions with the ability to tell vehicles when to move or to stop individually will make them more efficient, claims Carlo Ratti, director of the Senseable City Lab at the Massachusetts Institute of Technology (MIT). The smart junction moves the focus from flow at the level of aggregate traffic to that of individual vehicles. The car can change its speed as it approaches based on when the signal believes it will have a slot for the vehicle to sail straight through.

Research into the idea of slot-based junctions carried out by researchers at MIT, ETH Zurich and CNR in Italy used the same kind of queuing theory as that used to evaluate computer network switches. They tried strategies such as grouping vehicles into platoons and moving them as one rather than trying to interleave access car by car.

The most basic strategy – first-come, first-served – hit a capacity limit only 20 per cent higher than that of traditional light-controlled junctions. As traffic density increased, the batch strategy came close to doubling the capacity of the junction, though it would increase the waiting time for individual vehicles over the fairest strategy. The simulations also indicated that fuel consumption would fall as the scheduling scheme would, overall, lead to fewer vehicles idling at intersections.

Occupants might not like the waiting time of the platooning system but governments most likely will. Being able to increase road capacity would delay and possibly avoid the prospect raised in 2011 by Bill Ford, executive chairman of Ford. He warned of ‘global gridlock’ as the number of cars grows from one billion to a projected four billion by 2050.

Drivers on the M25 around London have already found that a road that changes its speed limit in response to traffic conditions reduces congestion overall. For much of the day, signs over the motorway at crunch points such as the junctions for the M4 and Heathrow Airport shift the speed limit up and down between 40mph and 70mph. According to Atkins Global, emissions fell between 2 and 8 per cent and the number of traffic-stalling shockwaves dropped from seven to five.

Vehicle-to-everything (V2X) technology lets the data used to manage roads make the final jump to the car itself. Not only will road signs talk to cars, the cars will talk to each other. It should make lane changing and merging onto motorways much safer. Small changes in apparent speed are today the key way to signal whether a vehicle on the main carriageway is moving to let you join. With vehicle-to-vehicle (V2V) communication, the car can send a message that says ‘go ahead, I won’t close that gap’.

The V2V messages can also act as a backup warning of a vehicle’s presence on the road when other sensors are providing inconclusive data. Demonstrations by V2V specialist Cohda Wireless, a spinout from the University of South Australia, used the signals to let vehicles announce their presence to others out of the direct line of sight. Cars heading towards a junction surrounded by buildings and other obstructions can tell whether hidden vehicles are likely to cross their path. Cyclists and pedestrians may start to wear transponders to signal their presence wirelessly around blind spots.

In November 2016, the European Commission published a list of functions it expects V2V and V2X to accomplish once the wireless networks needed to support them get up and running. Help for cyclists would probably have to wait for a second generation. But the commission built a list of ‘day one’ services that its researchers believe will provide a 3:1 benefit to cost ratio. The services include early warnings of slow or stationary traffic ahead, roadworks, sudden braking performed by vehicles in front and approaching emergency vehicles.

One major obstacle to a world where cars talk to everything on the road is a lack of reliable, high-speed radio communications. At the Eighth Future of Wireless Conference in London, held last year, David Wong, technology and innovation manager at the Society of Motor Manufacturers and Traders (SMMT) pointed out that less than half of the UK’s road network has 4G coverage.

The relatively easy part is making cars talk to each other. The motor industry has borrowed technology from the 802.11 Wi-Fi standards. Operating at close to 6GHz, 801.11p transmissions have a short range: just over 200m. The IEEE standards body responsible for it considered it good enough to provide cars with indications of when they want to change lanes or have to suddenly hit the brakes.

Rob Piechocki, researcher at the University of Bristol, says the committee halved the data rate to cope better with the Doppler shifts of fast-moving cars and made the process of connecting to nearby vehicles much faster, recognising they would often be fleeting links. Researchers at Bristol and other institutions are trying to find ways to supplement 802.11p cost-effectively.

One option is the cellular network, particularly with the upgrade to 5G that should start to get under way from the end of this decade and provide a further boost to data rates over longer distances. “Often it’s not about the data rate; it’s about providing reliability and connectivity. With cellular, it’s boom and bust much of the time,” says Andy Nix, professor of wireless communications at the University of Bristol.

But 5G is about more than bringing in new cellular protocols. A key theme of the 5G work is to make different radio networks work together. “We see ultimately the challenge being handled by a range of radios. You have 802.11p, LTE and millimetre-wave possibilities, ideally all being coordinated through software-defined networks. With multiple technologies, hopefully as one is weakening, another is kicking in,” Nix adds.

Millimetre-wave communications uses transmissions in a similar frequency range to that used for the radar sensors now being added to high-end vehicles. The big advantage of millimetre wave is that it allows very high bandwidths with less complex signalling than that needed for sub-5GHz cellular links. The downside is that millimetre-wave relies on line-of-sight communications, which makes it harder for receivers and transmitters to track each other. Imagine that moved to an environment where at least one of the transmitters is moving at 60mph.

However, the transmissions can be guided using electronic beamsteering techniques. The Bristol team is working with train operator First Group as part of the Mantra Project to see how the techniques work under a more controlled environment: that of carriages moving on rails. They can then adapt the system to handle vehicles on a road.

A big problem with millimetre-wave communication for fast-moving vehicles is initiating the conversation. “Think about two people in a dark room who can only communicate by flashing torches at each other and, at first, they don’t know where the other person is. They both have to switch on the torches and align them in the dark, and do it quickly,” says Piechocki.

Mixing networks provides a way around the problem. Sending coordinates derived using GPS over a cellular link will give vehicles a much better idea of where to focus the beams. The cellular link provides a way of authenticating transmitters before they come into range – wasting far less of the millimetre-wave channel’s bandwidth before the vehicle zooms back out of range.

The question then is who pays for the deployment of millimetre-wave transceivers by the roadside or on top of motorway gantries and for the additional cellular base stations? In the UK, local authorities have responsibility for implementing traffic-management systems. A survey of UK councils performed last year by Atkins found many are interested in V2X but have no plans to act on it until the technology becomes more tangible, and many are already struggling to find finance for projects. It is a problem that will be seen worldwide.

Reporting to the US Senate appropriations committee late last year, Nidhi Kalra, co-director of RAND’s Center for Decision Making Under Uncertainty, said: “There are market distortions in our transportation systems that mean we don’t take full advantage of the opportunities for cost-saving. Pollution is a real cost to our society. The question is who pays for it? While the market doesn’t take account of this, there is no incentive to fix it. We need to revisit things that are already preventing us from reaching these goals.”

Cities may find it easier to address issues of pollution and with it find money to pay for V2X infrastructure. Nix points to the maintenance of low-pollution zones: “A vehicle may have to have certain features to enter a city: intelligent engine management for example. The V2X technology can adjust the engine controls when it enters the zone. If your car can’t talk to the city, you pay a pollution tax.”

The same transceivers would inform vehicles of available parking spaces near the destination to avoid creating more pollution while driving around looking for one. Cities such as San Francisco and Santander have already begun to deploy the parking sensors that make such a system possible. Some cities may even use paid-for preferential access to junctions to recoup more of the investment. Dustin Carlino and colleagues from the University of Texas modelled one automated auction scheme that would allow vehicles to bid for fast-track slots at V2X-enabled junctions.

Cities may start to rip out intersections entirely and pedestrianise more of the urban space because the technology starts to reduce the number of vehicles entering the city overall. Planners in Scandinavia think it will be possible because communications will drive car-sharing and a reduction in personal vehicle ownership.

At the 2016 Nordic Smart Cities event, Krista Huhtala-Jenks, responsible for digital services at the Finnish Ministry of Transport and Communications, explained: “We need to get vehicle miles down but personal miles up. That means more people using shared access. If they travel in a car, the car will be full. That’s the reason why in Finland we are testing automated minibuses. They will act as the first-last mile public-transport solution for many people.”

The automated minibuses will travel around picking up and dropping off commuters where they need to go, to encourage them to avoid private transport. “We want more people using shared access. We need to solve that bit and change people’s behaviour before we have autonomous vehicles,” she added. Communication between the city and the transport will be one of the ingredients for moving to that point. But the future may equally be one where car owners bribe their way through junctions for a quicker journey home.

Anonymity on the streets

The one big advantage of V2V signalling is that other cars can work out exactly where your vehicle is and what it is going to do next. The big disadvantage is that so too can anyone else who gains access to the network, and, with a little additional effort, they can reshape the world around them.

Without effective security it will become too easy for a car to pretend to be an ambulance and carve a quick route through heavy traffic. Or for house owners fed up with the noise of passing traffic to declare there to be a roadblock outside and simply wait for satnav systems to reroute around them.

The problems of security go way beyond simply determining whether a transponder is fitted to an emergency vehicle.

Rob Piechocki, a communications technology researcher at the University of Bristol, explains: “When it comes to security, there are a number of competing requirements that need to be mutually satisfied. Privacy messes up many of the existing solutions: how do you provide authentication and security and also provide privacy?”

If the network cannot guarantee privacy, car occupants will be too easy to track – by governments, private companies and hackers. And that will slow down public acceptance of such systems.

At the same time, regulators and the industry do not want to give up the ability to collect data from vehicles. The car companies are keen to have vehicles providing live mapping data as they drive around to avoid the cost of managing fleets of dedicated survey vehicles in the way that Google does now.

Deborah Hersman, president and chief executive officer of the US-based National Safety Council, told senators late last year that the ability to retrieve and share post-crash data in a standard format is essential to the development of autonomous vehicles: “If you can’t access it, you won’t learn the lessons.”

Recognising the tension between security and personal data protection, the European Commission has made privacy part of its package of requirements for V2X. Unfortunately researchers have yet to come up with a way for a vehicle to declare it is legitimate without giving away an identity that can be linked to individuals.

One method is to use disposable pseudonyms and use those in combination with traditional public-key encryption.

“The interest is not so much in encryption but that we can trust the data being sent,” says Piechocki.

“If something is deemed untrustworthy, they will revoke the entire set of pseudonyms it holds. But that means keeping track of the valid pseudonyms. The open question is how do you deal with that without clogging up the network with security?”

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