When temperatures drop, it can be tricky to judge road conditions accurately. Soon, however, some roads could give drivers clear icy warnings by turning themselves pink.
A new temperature-sensitive varnish developed by researchers at French company Eurovia can be applied to road surfaces to warn drivers about dangerous conditions. The technique – still at the testing stage – might help prevent ice-related traffic accidents in future, the researchers say.
The varnish is made of a polymer containing a thermochromic pigment. The same type of coating is already used to make bath thermometers and frozen food packaging that responds to temperature change. However, it is the first time such a coating has been used to monitor road temperatures.
This winter, researchers at Eurovia tested the varnish on roads at different sites in France. They painted squares around a metre across onto the roads and observed how the normally transparent varnish turned dark pink when temperatures dropped below 1 °C (see image, right). When the temperature rose back above 2 °C, the coating became colourless again.
The beauty of the system, says project leader Thomas Devanne, is that information would be available in real time, allowing roads to be salted exactly where and when needed, or cautioning drivers to take extra care as roads start to become dangerous.
Devanne adds that the coating could be used anywhere that becomes icy in winter – on roads and highways, or even on pavements to warn pedestrians to watch their step.
“We have been proud to test this new coating, whose purpose is to make our roads safer,” Devanne told New Scientist.
“Our first on-site tests have produced some encouraging results – the coating is resistant to harsh weather conditions and is mechanically resistant too,” he says. “However, we have still have some work ahead of us to optimise the final product.”
The two most important challenges are improving the night visibility of the coating and ensuring it lasts throughout the summer months, when it would be exposed to higher levels of ultraviolet rays from the Sun.
“I think this is a very nice idea but the UV stability of the pigment used in these thermochromic materials will be one of the key issues to be addressed,” says Stuart Rowan of Case Western University in the US.
Rowan’s colleague Chris Weder points out that the team will also have to be certain of the accuracy of the temperature-induced colour changes.
“On beer bottles, thermochromics are really just a gimmick,” he adds. “However, Eurovia’s application, in contrast, strikes me as very useful and reflects some out-of-the-box thinking.”
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