Eco-responsible and safe roads could soon be a reality

Soon the long construction sites which, under the pretext of redoing the road, block traffic are over; no more municipal budgets swallowed up in illumination of empty streets at night; no more accidents on icy roads that have not been notified to the driver; no more polluting materials … In short, no more daddy’s road: technology now makes it possible to improve safety, sobriety and cleanliness.

In the light of the sun

It’s a small country road somewhere in the Landes, south of Dax. At first glance, there is nothing very original, at least by day. At night, on the other hand, it stands out, in every sense of the word. From 80 meters away, before you get into a bend, you can see two illuminated bands on the edges of the road. A special paint, developed by a Bordeaux start-up, OliKrom, was affixed a few weeks ago. By day, it stores light; at night, it returns it, for at least eight hours, signaling a dangerous turn. In Europe, this type of so-called “photoluminescent” paint already covers cycle paths. It even eliminates the need for night lighting!

A variant is called the “thermochromic” process. The promise is attractive: it is to coat the pavement with a product that changes color according to the outside temperature. In winter, the motorist can be warned of an icy road. But the authorities have ruled otherwise: too expensive, when a good sensor in the car already indicates that the road is icy, at least when it is likely to be.

A more profitable technique has been developed by Eurovia, a subsidiary of Vinci. Its name is quite a program: Power Road. The power in question is that of the sun. Its energy is absorbed during the day by sensors placed in the roadway. “It’s a kind of heated super-floor”, explains Nicolas Hautière, deputy to the director in charge of the R5G project (5th generation road) at the French Institute of Science and Technology for Transport, Planning and Networks (Ifsttar), a specialized body of Gustave-Eiffel University. In summer, the sensors restore energy to cool the tarmac and prevent it from melting; in winter, they heat it up, preventing the formation of frost. This process has been tested in particular on the A10, near the Saint-Arnoult toll, in the Yvelines region.

Another process aimed at improving road safety: by playing on the quality of the asphalt covering the road, we know how to make them more “catchy”. In bends, the tires grip them better. Some bitumens are also made to absorb large amounts of water. A mix developed by the Tarmac company acts like a very thirsty sponge: it can swallow 6000 liters of water per minute and per square meter! The system is however reserved for countries where the temperature is mild all year round: below zero degrees, the stored water can freeze and cause the road to explode, like a bottle of water in a freezer …

The pieces of a puzzle

The cities will take a little breath: it is now possible to reduce by up to 80% the bills for public lighting, which is the main item of expenditure for energy. What is this little miracle due to? To a system combining light-emitting diode (leds) lighting with sensors and a light-colored asphalt. Buried in the road, the sensors count the number of cars; Connected to these sensors, the lighting varies, to the point of turning off if no vehicle is reported. We can almost do without light thanks to the light color of the road …

The asphalt that covers streets and roads is an aggregate of different materials, the variations of which are endless: you can play on the space between the aggregates to reduce the noise emitted by vehicles, but also to improve tire grip. The communities, which pay for road repairs, however seem less sensitive to these advantages than a few years ago: demand is falling …

Each year, 70,000 kilometers of roads are renovated in France. Hence, each time, construction sites which scarred the roadway and slowed down traffic. Ifsttar has developed, with industrialists and two local authorities (Nantes Métropole and Saint-Aubin-lès-Elbeuf), a concept called “removable urban roadway”. The system is quite simple: it is a kind of slabs that fit together and come apart like the pieces of a puzzle. They replace the roadway, therefore limiting the trenches and those pesky deviations that never end …

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