Volvo used a stretch of highway in California to create a tongue-in-cheek advertisement about pinching energy from other cars on the road to power its SUV, the XC90 T8. The 300kW T8 is a plug-in hybrid that runs a four-cylinder turbocharged engine that gets an extra boost from an electric motor. Volvo set up rubber mats on the road in which tubes contain water. Passing cars run over the mats, squeezing the water through the tubes to run a generator which powers a charge station. A practical solution? Perhaps not. Would it work better in a city? Who knows. But it’s a pointer to the various roles electricity will have in the world of transport.