To say that cars could use smaller battery packs because roads would convey power is quite "short" sighted. Unless the distance between such charged roads were tiny, we would still need significant range from the batteries alone.
Further, the danger to people and wildlife from exposed charging rails is not negligible.
Additionally, as anyone who has traveled in North America knows, most roads are routinely ripped up and rebuilt - with the anticipated added cost of replacing major power-bearing infrastructure.
Engine-sized nuclear reactors are a better bet than this.
http://iheardacouplethings.blogspot.com 
