Some points they don't address:

    * Maintaining the high-friction surface of the glass as it is worn down
    * Keeping the road surface transparent to sunlight as it is abraded away and covered with dirt, motor oil and ground rubber
    * Huge energy requirements for melting snow, especially in areas where snow, ice and winter storms would reduce the energy generated by the panels
    * The _actual_ cost of their road surface compared to asphalt