In the 1930s, it took four years to complete the Golden Gate Bridge, the soaring span across the bay that connects Oakland to San Francisco.

It took less than a decade to complete the central water line from the Catskill Mountains to New York City, a mammoth 92-mile aqueduct and tunnel system worthy of the Roman Empire. That job was finished in 1915.

The first New York City subway line, stretching almost the length of the island and including more than two-dozen stations, opened in 1904 after less than four years of construction.

Contrast that with this: In April, officials broke ground on New York City's first new major subway line in three-quarters of a century. If all goes as planned - a big if - it will take six years to build the $3.8 billion first portion, a segment that runs 33 blocks and has just three new stations.

It will take far longer to build a small section of a new subway line today, even though we have state-of-the-art tunnel-boring machines and other high-tech wonders, than it did to construct the original line, which was built using workers with pick axes and mules to haul away debris. In fact, it seems to take far longer to build almost everything today - whether it be a bridge, road or shopping center. Your average enclosed shopping mall, which is not much more than a big empty box set on a parking lot, takes two or three years to build. Contrast that with the 102-story Empire State Building, an engineering marvel that's intricately decorated inside and out with art-deco metal, tile and brickwork and was completed in 1931 in a mere 13 months.

I've been thinking about this issue for quite a while, and I've collected a lot of anecdotal evidence that suggests that building times are much longer today - although it's hard to say for sure without doing years of serious research. But if I'm right, there are important implications for transportation. Progress - readiness for the future - usually involves the construction of big infrastructure projects, and if building big takes longer today, then that means improving our transportation system will take a very long time.

It's a strange phenomenon. We are richer and more technologically advanced than we were in olden days, which I think of as roughly before World War II. (Shoot, it took just eight years to build the Erie Canal, which opened in 1825.) Yet the richer we are, the longer things seem to take.

When I ask city officials and civil engineers about this, they agree with my thesis but have no satisfying explanations. The usual suspect is environmental and regulatory review, but I'm not including that in my perspective. I'm just talking about actual construction time.

Other advanced nations are experiencing the same phenomena. Things don't happen that quickly in Western Europe, with the exception of France, where the state has enormous authority to approve and build things on a short timetable.

Meanwhile, the emerging great cities of Asia, places such as Shanghai, Beijing and Mumbai, build at a pace that rivals the schedules of yore. Beijing, for example, had only one subway line a generation ago. When the Olympics open in 2008, it will have five major subway lines. Within a generation, it will have built a system that rivals those of London, Paris and New York. In and around Shanghai, new, elevated freeways appear practically overnight and entire new sections of the city are approved and built in a matter of months.

It's not necessarily all bad if it takes longer to do things today. Safety standards are probably higher. Pay, in relative terms, is probably higher. Perhaps a century ago you could throw thousands of workers on a project because they didn't expect to earn very much. But shouldn't machines make up the difference?

Funding appears to be part of the problem. We can't throw money at a project as fast as we used to. But how could this be, given that we are richer today than a century ago?

For the sake of fresh data, it will be interesting to see how long it takes to rebuild the elevated freeway sections that collapsed in April in San Francisco after a fuel tanker truck crashed and exploded. This is a very vital freeway connection that hundreds of thousands used daily. Will it take months or years to rebuild?

The best questions are those you don't have an answer to, and this is one of them. I look forward to ideas from readers.