in Brighton a tram would be a good idea for wide thoroughfares into the center: London road, Lewes road and the A259. you could terminate at park and rides at the edge of the city. but then, they could do that with a bus service. im not sure why trams are better than buses, they do seem to...
traffic and travel by road in central London, or pretty much any where, is horrendous. car travel is a either a luxury for those that prefer their own company or a necessity. price per mile isnt going to impact either group much.