22.–23.05.2024 #polismobility

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Csilla Letay talking to Prof. Nicolas Hautière, senior researcher at the Université Gustave Eiffel

View of a part of a solar-powered road at the Savoie Technolac Science and Technology Park
© Florian Pépellin – licensed under CC-BY-SA 4.0

View of a part of a solar-powered road at the Savoie Technolac Science and Technology Park © Florian Pépellin – licensed under CC-BY-SA 4.0

“Road infrastructure such as the pavement or the green verges can be used to harvest energy. This energy can be used as electricity for the power supply of the different sensors and actuators.”

Prof. Hautière, when talking about the mobility transformation, vehicles, automated driving technologies, car-to-car communication, intermodality and micromobility are usually in the public focus. Infrastructure is spoken about rather under spatial aspects – but the concrete ground the vehicles are and will be driving upon mostly does not feature. Why is that?

This is a complex or more precisely a systemic question. Indeed, the interactions between the vehicle, the driver and the road infrastructure are the basic principles behind the design of the roads we currently use. Therefore, you must foresee how people will move in the future to shape the road of the future. It explains why most of the discussions are dealing solely with vehicular aspects. For instance, the motorway has been designed for motor vehicles. If we are likely to move in a different way, we have thus to reinvent a new generation of roads. The question becomes a lot trickier when you are talking about the required road infrastructure for autonomous cars or electric cars. Some will devise that these cars should be independent from the infrastructure, whereas some others could devise exactly the contrary opinion. This becomes a controversy for public policy makers, who needs to be enlightened in their choices as much as possible. From a spatial planning perspective, this could also have some consequences on the occupancy rate of individual vehicles on city motorways and the possible increase of urban sprawl caused by unregulated new vehicle technologies.

At the symposium “Science meets City” embedded in the polis- MOBILITY event in May you gave a lecture on the topic “Smart Roads as a Strategic Issue for Tomorrow’s Cities”. Do European cities and municipalities have this issue in mind enough?

Most cities in Europe are aware of the impact of individual car ownership on motorway congestion and the associated environ- mental externalities, and they try individually to mitigate this problem at their own level of responsibility. This is usually not sufficient to solve such a problem, mainly because of two complications. First, the cities are not able to act on the road traffic, which comes from outside their geographical area. Second, the local administration which maintains the roads is not always the one that is responsible for public transport planning.

When we are talking about smart cities – what is the role of roads in these kinds of projects? What can they provide, how will they be embedded? The ideas range from novel building materials to digital networking and self-sufficient energy concepts. What can the road of the future realistically achieve?

The main solution is to develop an efficient public transport network – like the subway. Given the cost and time needed to build such solutions, the most efficient alternative is to progressively develop dedicated lanes on city roads and motorways, which would be restricted to shared, automated, and low carbon mobility solutions.

What intelligent services will – or could – they be equipped with?

These lanes would be equipped with sensor networks, especially camera networks, to manage traffic and count the number of passengers within the vehicles. Also, they will feature V2I communications to optimize the traffic flow. Since vehicles are likely to be progressively automated and always run at the same lateral position, there is a potential risk of faster degradation of the pavement. In this perspective, sensors in the pavement along with new road materials, predictive maintenance approaches, or even maintenance robots could allow to the development of better management strategies of road infrastructure.

With the road of the future, road infrastructure such as charging stations or lanterns could be supplied with electricity locally and independently. How can we use roads as energy suppliers for vehicles in the future?

Road infrastructure such as the pavement or the green verges can be used to harvest energy. This energy can be used as electricity for the power supply of the different sensors and actuators. It can also be converted to heat for the thermal control of the pavement or the rehabilitation of housing close to the road. The vehicles themselves could be powered by locally produced energy using dynamic charging technologies such as inductive charging.

Potholes caused by frost, heat-induced blow-ups, age- or material-related cracks in the road surface cause maintenance costs in the billions every year. As a result of climate change, extreme weather events such as long periods of heat are becoming more frequent and also place a heavy strain on the road network. We are currently seeing in Germany that the road infrastructure is outdated and that we have to renew it extensively and at length. We are in a perpetual roadworks mode, which also causes even more congestion than there already is. What will – in this context – become relevant for the construction of new roads and the reconstruction of existing ones?

Modular pavements can be a good solution to accelerate the construction of new roads and the reconstruction of existing ones. This type of construction allows to embed new technologies natively and is potentially easier to automate thanks to advanced robotics solutions. However, such a breakthrough solution is difficult to be adopted by road construction companies. As a consequence, at the moment, it is also much more costly.

How can new technologies such as sensors or IoT technology as well as new materials help avoid this high need for repair in advance?

Embedded IoT sensors in the pavement are potentially a good solution to develop more predictive maintenance strategies. However, the maturity of such solutions is still difficult to assess since the lifetime of sensors is still shorter than the pavement lifetime. Now, it is rather a reinsurance solution for road owners when they use new materials or increase the rate of recycled materials in the pavement.

Novel mixes for concrete and asphalt, the addition of microorganisms ... What materials and solutions will play a role in this? Which materials make sense from an ecological and economic point of view?

The development of asphalt pavement made of recycled aggregates combined with novel bio-binders is likely to become a rather big success – on the condition that these biomaterials do not compete with the agriculture surfaces devoted to human feeding.

By how many years could the „lifetime“ of roads be extended approximately?

This is a difficult question to answer. The recent experiments show that this kind of pavement has an extended lifetime compared to classic oil bitumen-based pavement. However, the accelerated testing facilities may not be completely relevant to assess such bio sourced materials. In addition, the resources are still too small to cover all the needs and new resources must be identified to upscale the solution. More generally, the smart road solutions allow to develop new predictive maintenance strategies, so that maintenance costs will be reduced due to the “non-linearity” of road aging. In a sense, we might say that the road of the future will be perpetual or “forever open”.

Which pilot projects can you name, for example?

The national I-STREET project is an industrial one illustrating the integrated approach we are talking about. At the European level, the Biorepavation project developed a novel bio bitumen pavement solution. The INCIT-EV project will demonstrate inductive charging technologies. The HERON project is developing a robot for modular pavement inspection and construction. The Augmented CCAM project will discuss the physical and digital infrastructure needed for automated mobility.

So, when it comes to implementing fifth-generation roads – are we talking about ten, twenty, or rather thirty years?

As we are facing climate change, we need to have solutions on the shelves as soon as possible and implement them within the next ten years. However, if we consider the fifth-generation road as one that can benefit from the best current and future technologies, we may enter a new paradigm of continuous innovation where such deadlines might be not relevant anymore.

Thank you very much for the exciting insights.


Ing. PhD Habil., is senior researcher at the Université Gustave Eiffel. He is in charge of the “Route 5e Génération Project (R5G)” and acts as Director of the Components and Systems Department (COSYS)

Prof. Nicolas Hautière © privat