During World War II the U.S. Maritime Commission built 2,751 Liberty ships, the relatively small cargo ships that were our supply lifelines for the war. They were standardized, mass-produced vessels assembled from 250,000 prefabricated parts. They cost about $2 million each.

Serving on these vessels was dangerous and less than glamorous. But the war could not have been won without them.

I thought of the Liberty ships while driving my 2004 Toyota Prius gas/electric hybrid for the Living Lite trip. I drove it from Dallas to Ensenada, Mexico, on to Los Angeles and back again. By the end of the trip, about 4,890 miles, I saw the Prius as my personal Liberty ship.

Why do I liken the Prius to a Liberty ship?

Consider the trip statistics. The 4,890 miles were done on 106 gallons of gasoline. It averaged 46.3 miles to the gallon. Most of the driving was done on high-speed interstate highways — like 10 in South Texas, 15 in California and Nevada, and 40 in Arizona and New Mexico. That means I was driving at 75 miles an hour much of the time. That's not economy speed, which explains why I didn't get the rated 50 miles per gallon on the highway.

The least expensive gasoline I bought was $1.599 a gallon in Fair Oaks, Texas; the most expensive was $2.299 in Ocotillo, Calif. The total spent was $199.65. The car, which charges its battery as you drive and switches to electric power when the gas engine isn't needed, performed flawlessly up and down mountains and across deserts. There were moments, driving down steep mountain grades, when I felt like a glider pilot soaring in magnificent silence.

The Prius also did well on the L.A. freeways and in cities. It loved the broad, level boulevards of Phoenix, averaging nearly 55 mpg for 100 miles. I also had the weird experience of watching the average mileage rise while driving from Santa Monica to Pasadena in rush hour traffic on "the 10." Moving at 5 to 20 miles an hour, the car pulled its power only from the battery.

Imagine the change in Los Angeles if everyone had a Prius. Rush hour might not be any faster, but thousands of people wouldn't be belching fumes in traffic.

My wife and I now have a small Prius fleet: We own two. One is vintage 2003. The other is vintage 2004. Assuming a total of 24,000 miles a year and former mileage of 18, the shift to 45 mpg cars has cut our gasoline consumption from 1,333 to 533 gallons, a saving of 800 gallons a year. If gasoline rises to $2.38 a gallon, the cash savings will pay the $1,900 a year it costs to insure both vehicles in Dallas.While having the 5,000-mile service in Glendale, Calif., the sales manager told me Toyota had added a production shift. They are now making these cars 24 hours a day, trying to keep up with demand. He also said — and readers confirmed — that some dealers are adding more than $4,000 to the sticker price of the car.

One Chicago reader wrote that he was getting his car in Wyoming, having written to dealers in a dozen states.The April issue of Technology Review, the Massachusetts Institute of Technology's magazine of innovation, features a Prius on its cover and tells us "Why Your Next Car Will Be A Hybrid: How Toyota Set The Standard for a New Auto Era." The May issue of Consumer Reports compares the car with four conventional sedans. It recommends the Prius.

There is only one problem with this Liberty ship.

It is produced in Japan.

Ford will introduce an Escape hybrid in September. GM will introduce a Silverado hybrid at the same time. Detroit's response has been slow and reluctant. Washington's response has been worse. This has allowed Toyota (and Japan) to gain precious years of field and production experience.

If oil prices remain high, Detroit will be flat-footed and we'll be hemorrhaging from two arteries. We'll be paying up for oil. And we'll be importing the cars that use less of it.

Historians won't be kind.