For more than five decades, the average number of miles driven annually by Americans increased year by year, until around the turn of the century, when our driving habits suddenly headed in reverse. According to a new study released by US PIRG, American drivers logged 6 percent fewer miles in 2011 than they did 2004, a trend that is particularly pronounced in young people:

From 2001 and 2009, the average annual number of vehicle-miles traveled by young people (16 to 34-year-olds) decreased from 10,300 miles to 7,900 miles per capita – a drop of 23 percent. The trend away from steady growth in driving is likely to be long-lasting – even once the economy recovers. Young people are driving less for a host of reasons – higher gas prices, new licensing laws, improvements in technology that support alternative transportation, and changes in Generation Y’s values and preferences – all factors that are likely to have an impact for years to come.

Federal and local governments have historically made massive investments in new highway capacity on the assumption that driving will continue to increase at a rapid and steady pace. The changing transportation preferences of young people – and Americans overall – throw those assumptions into doubt. The time has come for transportation policy to reflect the needs and desires of today’s Americans – not the worn-out conventional wisdom from days gone by.

Yes, average annual mileage may recover somewhat with the economy, but a generation of Americans have learned that the automobile is not as freeing as it's cracked up to be. According to AAA, the average total cost of car ownership was $8,776 in 2011. By comparison, a transit pass costs about $100 a month. That's a lesson that will be hard to unlearn.

The viaduct, the 520 bridge, and the 405 widening projects are all under way, but one gets the feeling that this may be the last burst of major new highway construction in the region for quite some time if ever. Meanwhile, we're about to remove lanes from the I-90 bridge, and convert them to light rail, not because car-hating socialists are engaged in social engineering, but because the people demand it.

Transportation preferences are changing, especially among young people. And slowly, our transportation policies are changing in response.