The gist: The best-kept secret among transportation experts is the near-universal agreement that variable tolls--known as congestion pricing--offer the only real solution to worsening gridlock.

The details: With congestion pricing, phantom tollbooth scanners deduct tolls from prepaid smart cards posted on cars' dashboards; the tolls would rise as rush hours approached and taper off as traffic dwindled.

Demonstrated in Ontario and southern California--and recently installed in London--such tolls could generate enough revenue annually to offset many local taxes while easing the congestion that annually squanders more than hundreds of millions of hours of time and gallons of gasoline in Northwest cities.

The keys to public acceptance of congestion pricing are creating pilot projects for drivers to experience and first making toll lanes available where there are also free lanes.

A Northwest reality?

Congestion pricing is inching closer to reality in the Northwest. In Washington, the Puget Sound Regional Council is conducting a pilot project to apply congestion pricing in transportation planning.

One reason to believe traffic taxes will ultimately arrive in the Northwest, even if piecemeal and incrementally, is the lack of alternatives.

For example, even if the citizens of greater Seattle tax themselves almost $1 billion extra each year, for mass transit, roads, and other transportation improvements as specified in the region's approved master transportation plan, afternoon gridlock will still spread to almost half the freeway network in the central Puget Sound region by 2020.

The time residents spend stuck in traffic will triple; average freeway traffic speed will fall to 21 miles (34 kilometers) per hour. Tolls, on the other hand, could tame congestion even while generating enough money to repeal local sales taxes.

Read recent updates on congestion pricing on Sightline's blog.