Cities are looking for ways to make themselves cleaner, greener, and more sustainable. So cities here and there are trying out pilot projects and even have permanent installations that other cities should seriously look at, like installing solar panels in places you wouldn’t think of otherwise.
Cycling is a popular hobby in the Netherlands. As such several companies combined forces for the installation of bike pathways that can collect harvest solar power to go back into the grid. The project consists of concrete panels topped with glass; there are silicon solar cells between the glass and concrete designed to trap energy of over fifty kilowatts annually per square meter. Although it doesn’t appear to be much, eventually the paths could cover over a hundred and thirty seven kilometers of the pathway.
Other projects include solar-powered markets that can set up anywhere, architectural designs that employ passive cooling and water collection, wind farms, and capturing storm water. Read about all of them at Housely.
https://en.wikipedia.org/wiki/Watt#Confusion_of_watts.2C_watt-hours_and_watts_per_hour
Also I don't know where the figure came from. After some googling the 75 meter road (240 feet) produces 3000kWh for the first half year = 41W/m:
http://www.triplepundit.com/2016/01/looking-at-the-dutch-solar-bike-path-after-one-year/