It's a well known feature of transportation planning that traffic expands to fill available road space: http://www.culturechange.org/issue8/traffic%20expands.ht

It's a well known feature of transportation planning that traffic expands to fill available road space: http://www.culturechange.org/issue8/traffic%20expands.htm http://www.culturechange.org/issue8/traffic%20expands.htm The argument is, if the traffic is just going to expand to fill the new roads we build, then why not build more densely instead and help people have shorter commutes. Also some arguments around vicious cycles of building more roads, leading to more traffic, leading to demand for more, bigger roads, etc, vs. supporting biking/walking/public transit