Axle sensors

Off to Renfrew yesterday afternoon to deposit accumulated cheques (our banks are there, not here); between the Ontario-Quebec border and Renfrew we passed over no fewer than six pairs of parallel cables stretched across the road. I was going to Ask MetaFilter about it when we got home, but it turns out the question has already been asked, and answered: they’re axle sensors, which measure traffic and average speed. These were all on county roads; I wonder what they’re up to.