While digital technologies are transforming vehicles and how we interact with them, they are also reshaping city transport infrastructure. Smart infrastructure technologies, collectively known as intelligent transportation systems (ITS), are being embedded in traffic lights, car parks, toll-booths, roads and bridges, making them increasingly able to communicate with each other and with the vehicles that use them. Together these innovations offer the prospect of a transport infrastructure system that suffers less congestion, is safer, and can be maintained predictively.

How can circular economy principles be applied to take full advantage of such intelligent assets and help them contribute to wider smart city solutions? A large part of the answer lies in letting a highly networked transport system behave more like an ecosystem than a mechanism, relying less on top down control and more on local rules in an environment with rich feedback between vehicles and the infrastructure on which they rely.

Keeping the traffic and the information flowing

A circular economy, like an ecosystem, lacks an overarching controlling influence and is rich in feedback. How can these flows of information be used to make a transport system more circular? Take traffic lights. Helbing and Laemmer show that putting digital sensing and communication technologies in a set of traffic lights allows cars to control the lights rather than the other way round, reducing average delay times by up to 40%. This perhaps surprising result stems from the fact that traffic is a complex adaptive system. It turns out the most effective way to manage such a system is to make each set of lights subject to some simple ‘bottom-up’ rules, such as recognising ‘platoons’ of cars coming towards it and prioritising their passage, and to let the system achieve an emergent (dynamic) equilibrium by itself. Even state of the art mechanisms that control light sequences ‘top-down’ still reply on average rather than actual traffic patterns – even if they take account of rush hours for example – and so will under-perform the simple rule approach. The whole system is simply too complex to optimise in real time – the necessary computations are beyond even a supercomputer. Such an approach also cannot respond as nimbly to a shock to the system such as an accident.

Photo credit: _Sredni_Vashtar_ via Visualhunt.com / CC BY
Photo credit: _Sredni_Vashtar_ via Visualhunt.com / CC BY

The benefits can be extended to two-wheeled vehicles. Copenhagen, where half of all residents commute by bike is installing 380 smart traffic signals that can prioritize the progress of cyclists through traffic to speed up their commutes. Sensors can detect a platoon of bikes approaching an intersection and allow it through by signalling the lights to turn green, and continue to do so along certain routes to give the platoon an uninterrupted journey, adjusting the timings of the lights using data from cameras that estimate the cyclists’ speed. The city expects the signals to reduce travel times by 10% and hopes they will encourage yet more commuters into the saddle.

While smart traffic signals outperform pre-programmed ones, once the flow of information grows further they could become obsolete altogether. Modelling by the MIT Sensable Lab has shown that autonomous intersections can merge flows of sensor-laden self-driving cars using a slot-based system, replacing traffic lights with precisely directed streams of vehicles, potentially doubling the number of cars that could safely use an intersection over a given period.

Traffic infrastructure can also use bottom up rules and data flows to increase safety. Endowing traffic lights with digital collision avoidance systems would allow them to recognise when a crash between two approaching vehicles was imminent, based on their trajectories, and warn the drivers or – in future – even directly activate their vehicle’s brakes. A similar approach can be taken to speed limits. Intelligent speed adaptation (ISA) helps a driver keep to the limit by correlating information about her vehicle’s positions over time with a digital speed limit map to determine her speed. The system can warn a speeding driver using traffic signals, or even slow him down automatically if his car is self-driving. France has developed an ISA system that automatically slows fast-moving vehicles (via traffic signals) in extreme weather conditions.

Using digital technologies to systematically decrease congestion but increase safety – and reduce the often unpriced negative effects on public health and the climate due to  the emissions from idling cars – has a sizeable economic benefit. In the U.S., it is estimated that traffic jams cost USD 10 billion a year and waste more than 10 billion litres of fuel (Helbing). Minimising such negative externalities is a core principle of a circular economy. Wider economic benefits can also be won: a 2009 Reason Foundation study found that reducing congestion and increasing travel speeds enough to improve by 10% access to regional employment, retail, education and city centres increased production of goods and services in that region by 1%.

FlickrCC: Glen Scott
FlickrCC: Glen Scott

Smart pricing, smart investing

Digital technologies that systematically reduce congestion by increasing flows of information serve to increase the efficiency with which transport infrastructure is used. They can also be harnessed to set prices for that usage at busy times to further improve traffic outcomes. Smart toll-booths that can sense traffic flows could potentially be used to set differential prices in real-time for using a section of road or a bridge. They would indirectly price the negative externality of congestion to optimise traffic flow (though implementation would need to carefully consider issues such as availability of alternatives, price limits and distributional effects among drivers).

A similar approach can be applied to parking spaces. The app SFpark, developed by the San Francisco Municipal Transportation Agency, tracks vacant parking spaces in 15 of the 20 city-owned parking garages (covering 12,250 spaces), and in 7,000 of the city’s 28,800 metered car park spaces, setting their prices in real time according to availability and demand. Charging for parking in the first place has an economic benefit to those on low incomes, according to UCLA economist Donald Shoup. He argues that the cost of building large lots for free parking outside, for instance, apartment buildings and supermarkets increases rents and grocery prices respectively, effectively forcing those unable to afford to drive to subsidise those who can.

The investment case for a real-time information traffic management system, including elements such as those discussed, seems clear. The U.S. Government Accountability Office estimates that establishing such as system in all states and the country’s 50 largest cities would cost $1.2 billion and provide $30.2 billion worth of benefits to mobility, the environment, and safety – a benefit-cost of ratio of 25:1. Making such an investment counters the structural waste in the transport sector of an infrastructure capacity that is at once over-sized (most of the time) and congested (during busy periods).

Giving roads a voice

Another type of structural waste in the transport infrastructure system is the disruption caused by unplanned maintenance. ITS technology helps here too. Smart sensors can assess the state of repair of roads and bridges, for example, communicate that to their manufacturers, and thereby facilitate the on-demand planning of repair, refurbishment and remanufacture activities. This avoids waiting until a piece of infrastructure fails, or having to follow an unnecessarily frequent planned repair schedule. Such an approach increases the feasibility of product-as-a-service type business models and the ability to unlock their increased resource productivity and profitability.

FlickrCC: Paul Jansen
FlickrCC: Paul Jansen

One way to generate the feedback necessary to such systems is to make vehicles sensitive to infrastructure conditions. In Boston, a smartphone app called Street Bump identifies potholes from data collected when cars drive over them and automatically sends their locations to the transport department. The infrastructure itself can also get smarter. New highly sensitive piezoresistive sensors, which measure changes in electrical resistance, can be embedded in the concrete of a bridge to monitor the stresses on it. The sensors not only provide data wirelessly to traffic managers on the bridge’s load bearing capacity, but also provide engineers with a stream of real-time data about the health of its structure. In the event of an earthquake, for instance, the sensors can assess the bridge’s dynamic performance, and help determine its residual capacity.

Drivers can also benefit directly from road infrastructure data. The Finnish company Vaisala has designed infra-red laser sensors that can be embedded in a road surface to measure its temperature and assess whether it is covered in ice, snow or water. The data are transmitted to traffic management systems that can alert drivers to adverse conditions via overhead signs. The information generated by mobile devices could provide data required to optimise resource management. This enhanced visibility means that damage assets can be minimised or prevented and infrastructure improved.

Plugging into the city

Flows of vehicle-to-infrastructure information can extend beyond transport. Nissan is launching a pilot project in the UK where 100 of its Leaf electric cars can be plugged into the national electricity grid, allowing motorists to charge their cars and allow the batteries in them to act as additional grid capacity, helping meet demand at peak times by selling power back to the grid. This increases the grid’s diversity and therefore resilience, a central pillar of a circular economy. The effect can be further bolstered by adding smart sensors to the grid to track disturbances and quickly re-route power in the event of failures, and by installing smart meters in homes to offer both lower tariffs when demand is low and payments to reduce usage when it is high.

Paradoxically, few of the technical advances in transport infrastructure will change the look and feel of cities. A set of traffic lights that has smart sensors looks much like one that does not. Sensors embedded in a bridge will be largely invisible. Rather it is innovation in virtual networks that will have the most visible effects. The city of Helsinki is aiming to render car ownership obsolete by unlocking the ‘ecosystem of mobility’ in the form of a ‘mobility as a service’ app that uses real-time information on availability and price to enable citizens to plan and pay for their journey – by bus, taxi, ferry or bike – more cheaply, efficiently and with greater flexibility. Such ‘ambient technology’ will reduce the size and importance of central stations and increase that of decentralised transport nodes. But it is the substantial shrinking of the car fleet caused by the advent of autonomous vehicles (in optimistic projections) that could free up whole lanes on city streets (by eliminating parked cars) and reclaim space allocated to parking lots and home garages, that could bring about the more fundamental change to our cityscapes.

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The Author

Ian Banks

Ian Banks

Ian is an editor at the Ellen MacArthur Foundation, where he was part of the teams that prepared 'The New Plastics Economy’ and ‘Delivering the Circular Economy - A Toolkit for Policymakers’ reports. Previously he worked at a consultancy largely on climate and energy economics.