David Levinson:

Remember traffic. It was only 30 years ago that people were complaining about getting stuck in traffic. But traffic peaked in the early part of the Century, and has fallen ever since. A few observers picked this up early, but many transportation agencies were in denial.
 At the time, most analysts saw only two possible futures:
 Future 1: Per capita vehicle travel resumes an upward path. This forecast was the proverbial ostrich with its sand-encased head.
 Future 2: Per capita vehicle travel remains flat but traffic grows with population. Future 2 was already causing concerns as it created pressures on revenues (which were then dependent on falling gas tax revenue), yet DOTs still claimed needs for new construction and expansion of existing roadways despite overall falling demand. Some argued that though demand was falling on average, it wasn’t mean it is falling everywhere. And there were still unsolved problems that don’t go away just because travel isn’t increasing.
 No one in power foresaw what actually happened.
 Future 3: Per capita vehicle travel falls significantly.
 At first people attributed this to the Great Recession of the late Bush Presidency, but the evidence was that travel began dropping before the economy tanked. Technology restructured personal travel the way it completely devastated many other industries (remember newspapers, the post office, buying records and paper books, your land-line phone, canals, long distance passenger trains, broadcast television, electric utilities, going to College). Just look at this picture of demand for mail: