Many options, no single solution to nation's traffic snarls

Ridership on public buses, trains and subways has reached its highest level nationally since the 1950s, and transit boosters cite this as evidence that expanded service and routes is a good investment.

To help fund new construction, the Obama administration has proposed letting states toll federal interstates.

New vehicles will increasingly be "smart cars," equipped with wireless technology that lets them share how fast they're going, their direction, whether they're braking and whether an accident just happened ahead.

Ford, Toyota and other automakers are working on the technology, but it could easily take a decade or more after smart cars hit showrooms before they replace enough older vehicles to realize their full benefits.

The University of Michigan Transportation Research Institute is setting up a mock city to test the technology in artificially dangerous situations like a truck running a red light.

"Self-driving" vehicles hold the potential to provide new mobility for the aged and the disabled, and reduce the demand for parking because they could be summoned by other users.

Nearly 80 prototypes have permission from the California Department of Motor Vehicles to test their skills on public roads, although a person must sit behind the wheel in case the on-board computers and sensors make a mistake.

While some Silicon Valley companies want to see these cars proliferate in the next few years, traditional automakers are taking an incremental approach by adding features such as automatic braking or lane-keeping on newer models.

Boston's public schools have experimented with an app that tracks how soon the school bus will arrive so parents who don't want their kids to wait in the cold too long can time drop-offs rather than opting for a drive all the way to school.