Installation costs of building such roadways and parking lots are expected to cost at least 50 percent more than regular roads, and possibly more. Maintenance costs will also be higher because road surfaces accumulate rubber, salt, soil and other substances that block sunlight and must be removed. The durability of the panels may also be less, further increasing maintenance costs. In addition, the solar roadways system is designed to replace many other road features that also cost drivers for road systems.
On the other hand, how will the technology develop once a lot of other very smart, ambitious people and some big companies get involved?
Kind of related: "Why Owning Your Own Power Plant Might Not Be Crazy".