A small start-up called Solar Roadways is seeking funding to commercialize what looks like a revolutionary idea – smart roads made of glass that generate power, can be programed with all the usual information that roads have now (and more) and which stay clear in winter (though micro-heating elements). It’s one of those inventions that looks amazing but of courses raises a lot of questions: what is the EROI (energy return on investment – i.e. will they actually use more energy to construct and maintain than they generate)? What is the longer-term lifespan of the elements? And does the ‘two-way communication’ capacity of these roads mean that all roads would also be automated surveillance devices – and is that a problem?