Comment by ksplicer

This would only be true if additional lanes were built on top of each other instead of next to each other. As lanes are widened though they just keep pushing things apart and making other types of transit less pleasant, which will then create demand that wasn't there before (because people now need to be on roads longer to get where they want to go). There is a maximum density that cars can support that is LOWER than most cities are built up at.