[Paladin2]

Many times adding a lane significantly improves congestion, at least for a few years. All one has to do is plan for the space to put lanes and build them in advance of the demand (typically not done due to liomited resources).

There are plenty of places where there was traffic congestion prior to building the interstates that have been successfully relieved by an interstate built in the 1960's. The congestion is still gone 40 years later while the number of lanes hasen't been increased. Think of Iowa, North and South Dakota, Montana, Nebraska. Especially river crossings.

[Alberta's Child]

Take a look at one of the annual reports prepared by an organization like the Texas Transportation Institute that details the most congested segments of roadway in the nation. You could widen every one of those roadways to 40 lanes per direction next week, and within 5 years they would be operating at the same level of congestion as they are experiencing today.

It's simply the nature of how things work. It's a principle in economics called "The Tragedy of the Commons."

Haven't you ever wondered why littering along a highway warrents a special statute in most states? It's because many people who wouldn't even think of dropping a single cigarette butt in their own back yard think nothing of littering in a place that "nobody" (or "everybody") owns.