06:55 AM PDT on Wednesday, May 24, 2006

ALLEN SCHAUFFLER / KING5.com

SEATTLE -- Every morning and evening on Western Washington roadways it's painfully clear that there are too many vehicles and too little space. 

Mark Hallenbeck oversees the traffic research center at the University of Washington, and he has a surprising formula to illustrate it.

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Start with everyone who would like to drive I-5 through Seattle at peak commuting hours.  This includes people who have changed their work schedules or resorted to other forms of transportation to avoid the traffic.  Then assume that all of these people could drive at a brisk 70 miles an hour.

How big would I-5 have to be to accommodate all that traffic at that speed?

"What you really need are 22 lanes," Hallenbeck said.  "In one direction."

And as the population continues to grow, traffic is only going to get worse. That's why the Washington State Department of Transportation will soon launch a pilot project on Highway 167 to experiment with high occupancy toll lanes, or HOT lanes.

Here's how it works. As traffic slows, drivers have the option to switch into a HOT lane, but it will cost them. Electronic reader boards display the price for entering the lane, and prices change with the traffic. The greater the traffic, the higher the prices.

When a driver enters the HOT lane, sensors detect a chip on the vehicle's windshield and deduct the toll amount from the driver's account. Carpoolers and busses will not be not charged.

Hallenbeck predicts that giving drivers the option to move into the HOT lane would "get about 13 percent more vehicles through," therefore reducing traffic pressure on the roadway.

KING 5

A computer rendering of the Ship Canal bridge with 22 northbound lanes of traffic.

"I think we'll find there will be a lot of resistance to congestion pricing initially," Hallenbeck admits. "But sitting in traffic for free is still an option." Prices would range from approximately $1.50 to $3.50.

San Diego, Minneapolis and Houston are already experimenting with HOT lanes. WSDOT plans to begin the pilot program along Highway 167 sometime in 2008.