Road vs Rail

As urban areas grow, efficient transportation becomes more of a challenge. Patterns of growth among other things probably play the largest role in determining the kind transportation that would suit a given region. Cities need to plan for growth by appropriately building the required transportation infrastructure. In the US, any such proposal for building infrastructure is put to vote. There is an ongoing debate in many cities in the US, where residents are choosing between rails and roads. Rail makes sense for densely populated areas, roads make sense otherwise. But I guess the problem lies with the definition of "dense". Obviously density has to be studied on a case by case basis and cannot have a general threshold value. But thanks to the politics involved, people on either side of the debate paint a black and white picture. As a result there are so many biased views, and its hard to see what the real issues are.