I'm sure you all have seen them, I just wonder if anyone knows what they do: I have noticed traffic sensors of some sort in various places over the last few months. They consist of two long wires which look like co-ax cable duct-taped across the road/street/lane/highway. They are connected to a box which is left on the side of the road (usually padlocked to something). The box is powered by a small array of solar cells on top. Anybody know what they do? I first thought they might be checking speed, but then they started showing up on highways. My hunch is that at highway speeds and volumes (and lane crossings, etc.), a device would need more computing power than could be provided by solar cells to decipher wheel passings and convert to average speeds. They may be checking volume - counting up the # of axles which pass by the sensor. But then why would it need two cables, and why have I seen them sometimes only going into 1 lane on the highway? I'm just curious if I should be speeding over them to mess up the data collection or not.