The city with the nation's highest parking tax (50 percent) should think about building a project unprecedented in transportation history: the world's biggest parking garage, a 40-story skyscraper in the heart of Downtown Pittsburgh.

Each floor would contain 1,000 parking spaces. Floors one-10 would provide a direct ramp to and from the Parkway North; floors 11-20, the Parkway East; floors 21-30, the Parkway West; and floors 31-40, the proposed Mon-Fayette Expressway serving points south.

A futuristic 40,000-space parking hub in the dilapidated Forbes-Fifth corridor could be a tribute to the oil industry in the original home of Gulf Oil Corp. A tourist attraction as high and wide as Egypt's Great Pyramid. A shrine to our love of automobiles. A symbol of the American way.

Why not?

I mused about the far-fetched idea after reading about a Feb. 17 ground-breaking for a 1,500-space, $37 million parking garage that the federal government is building for the VA Pittsburgh Healthcare System in Oakland.

Researching the PG's news library showed at least 16 parking garages are under construction or have been built here since 2000.

It wasn't possible to determine exact numbers, but we're talking at least 16,000 new spaces costing more than $300 million in parking garages alone!

This doesn't count four parking garages with 2,510 spaces the Pittsburgh Urban Redevelopment Authority wants to add at the Pittsburgh Technology Center along Second Avenue.

This doesn't count private and public parking garages built in the city before 2000. And it doesn't count private and public surface parking lots, many of which have been expanded or upgraded.

Building one really gigantic parking garage would make Pittsburgh the "World's Most Parkable City."

The recent parking garage building boom is as an indication -- if not a wake-up call -- of where the region's transportation policy is headed.

Under construction

The 1,500-space garage that's part of a $200 million Veterans Affairs project in Oakland.

A 1,050-space, $35 million garage the Pittsburgh Parking Authority's building at 11th Street and Liberty Avenue, along with a new Greyhound Bus Terminal.

The Stadium Authority's 1,255-space, 10-level, $29 million garage at Reedsdale and West General Robinson Street, on the North Shore, including space for a light-rail station that may not be built.

UPMC's three parking garages, including an 800-space garage just for staff, as part of a new Children's Hospital in Lawrenceville.

Recently constructed

2000 -- Mellon Bank opened a privately owned, 650-space garage, part of a new Client Service Center on Ross Street.

2001 -- The Sports and Exhibition Authority opened a 925-space, $22 million garage on General Robinson Street, near PNC Park.

The Pittsburgh Parking Authority opened the 1,240-space, $18 million First Avenue Garage, incorporating a light-rail station in the design.

2003 -- A 710-space garage opened at the David L. Lawrence Convention Center, part of the $375 million new center.

The Pittsburgh Cultural Trust opened an 800-space garage on Penn Avenue.

2005 -- Phipps Conservatory and Botanical Gardens in Oakland opened a 200-space garage.

Albeit in the suburbs, the Port Authority opened a 2,200-space, seven-level, $24 million garage next to the South Hills Village light-rail station, the largest garage ever built in Western Pennsylvania.

At the SouthSide Works, private developers opened the last of three parking garages built within a three-year period -- the Furnace, Ingot and Hot Metal garages.

On one hand, the frenzy to add parking seems understandable. Recent U.S. Census Bureau figures showed more than 180,000 suburbanites a day flow into Downtown, Oakland and other neighborhoods, boosting Pittsburgh's population by 41 percent, the fourth-highest proportional "day surge" in the United States.

On the other hand, about half of those people commute by bus or trolley, again one of the nation's top percentages.

Building parking like there's no tomorrow seems paradoxical when:

Thirty-four percent of the bridges in the 10-county region are obsolete and/or structurally deficient; outdated traffic signals cause drivers to burn 12 percent more fuel than necessary; the two-mile Route 28 "missing link" between East Ohio Street and Millvale is still on the drawing board after 30 years; and the Port Authority will face the biggest money crisis in its history at the end of the year.

But I'll make you a bet.

When a gambling casino comes to Pittsburgh, one of the first things to be built will be a giant parking garage.

Trip back in time. Because of growing popularity, the nonprofit Pennsylvania Trolley Museum is expanding the schedule for its 2006 season and 43rd year of operation.

"We have really been growing, with attendance last year of over 21,000 visitors," said Scott Becker, executive director of the sprawling facility near Washington, Pa.

But opening earlier and adding Mondays and Fridays in spring and fall, rather than weekends only, means the museum needs more volunteers to sustain its public programs.

Two-hour "volunteer open houses" will be held at 1 and 7 p.m. Tuesday and again at 10 a.m. Saturday for people to learn about volunteer opportunities, from selling tickets to rebuilding old trolleys. In 2005, more than 150 people contributed 26,000 volunteer hours.

The Pennsylvania Trolley Museum's collection has grown to almost 50 trolleys from as far as Brazil and two miles of active, operating trolley line at the Meadowlands off Interstate 79. A 28,000-square-foot trolley display building opened last year.

Mr. Becker asked prospective volunteers to contact the museum by e-mail at vsm@pa-trolley.org or by calling 724-228-9256.

Elsewhere. Twenty municipalities in the Kansas City, Mo., area have created Operation Green Light, a $13 million effort to coordinate traffic signals on busy highway corridors during morning and evening rush hours.

Believe it! On June 29, 1956, President Dwight Eisenhower signed the legislation creating the nation's interstate highway system. Now, 50 years later, the system contains 42,800 miles of limited-access roads criss-crossing the country.

Plate du jour. Dave Williams, of Murrysville, is UP2HERE. That's his Pennsylvania personalized license plate. "Take it for what it is," he e-mailed.