Highways always stay busy around the world. There are over a billion vehicles on the planet with no shortage of them on the road at any given minute. In the United States alone, there is over 160,000 miles of highway. If you think about how many cars travel at high speeds every day on these roads, you will realize that is quite a bit of potential energy from wind. Why not take advantage of this wind that can be generated from guaranteed traffic, especially in the higher speed and high-volume zones.
Highway windmills can be a great solution. There is much potential but probably not much utilization of this source of wind power. There are many different configurations of vertically or horizontally oriented windmills that can be placed along the upwards rising embankments or fixed to noise barriers. Highways with fast moving traffic and high-volume would serve as an optimal solution. Slow moving and high-volume traffic would still be acceptable in the inner cities and fast moving and low volume traffic should work well out in the countryside. Proper spacing is critical for the optimal air flow in this situation. The ideal placement will have to be analyzed using computational fluid dynamics software and calculations.
Highway windmills will be ideal for electricity generation and storage and will not really take up any extra space. All the lightning along the roads could be easily powered by some of these windmills. Stored energy could be sent down to all the small towns along the highways in the rural areas and to nearby city blocks in the dense urban and industrial areas. There would be almost no pollution from these windmills, except for some noise. Highway noise is already an existing problem, so the impact should be minimal. Birds do not typically get close to highways so any wildlife impacts would also be minimal. Overall this is a unique solution coming from the utilization of existing infrastructure.