First off it should be recognized that driving as we do it today, has zero reclaimed energy.
Energy harvesting road systems could easily follow a technological curve similar to computers and genetic mapping .
That is to say it could double in energy production every 2 years or so.
Israel has taken the idea and produced road rail and sidewalk energy harvesting systems. http://www.kurzweilai.net/innowattech-harvests-mechanical-energy-from-roadways
Other concepts can be integrated for safety.
even systems that could prevent road kill .
also it should be noted there is more than one way to make roads that harvest energy. starting with thin film solar and piezoelectric to mechanical systems such as Road Power Generation.
Jerry Brown had a chance this week to sign a bill to foster these advancements but sadly he veto'd it.
This little video touches on our current Energy state.
