When the federal government announced less than two weeks ago that California would get $2.25 billion to help develop a high-speed rail system, it made me wonder if the time has finally come for this good idea.

If built, California’s high-speed train, or HST, would be of great interest to the state’s business and political leaders. After all, you could board a train in Los Angeles, speed along at up to 220 miles an hour, and arrive in San Francisco a little more than two hours later. Spurs would go to other cities, such as Anaheim, San Diego and Sacramento.

Alas, the more I read up on it, the more I felt like I had boarded the blue train that Johnny Cash crooned about. There’s a real funding question and a seriously optimistic view of the ridership.

But let’s start with this basic question: If the HST existed and you were planning a trip from Los Angeles to San Francisco, why would you consider boarding it?

Well, the cost of an HST ticket is projected to be 83 percent that of an airline ticket, so the train gets the nod on price.

However, if you were taking a family trip, you would likely take a car. It’s a much better deal, particularly if you have multiple kids.

If you were taking a business trip, you’d probably care less about the cost and more about the convenience of the train schedule vs. that of the airlines. We don’t know the train schedules yet, but since planes fly from LAX to San Francisco all times of the day and night (Southwest Airlines alone flies 11 times a day there), airlines would seem to have the advantage. A trip by air would be about an hour shorter than one by the HST, too.

Surface transportation to and from a train station is a wild card; it may be more convenient than the airport, but that depends on where your house or office is located. And let’s assume security procedures at an HST station would be about as rigorous as at the airport. (If not, I wouldn’t want to board the train.) So there may be no time saved there.

In short, the HST is no category killer. It would complement, not replace, your other transportation choices.

Yet the official projections assume it would dominate all forms of transportation and then some. The California High-Speed Rail Authority projects 13.5 million riders in the first year of operation, 2020, and 41 million by 2035.

Think about that smaller number, 13.5 million. In all, there are now only 8 million trips – by air and by car – each year between San Francisco and Los Angeles, estimated one expert at a panel last fall at the University of California at Berkeley.

Maybe the 8 million number is low, and let’s assume the HST would draw passengers from more that those two cities. But consider the Acela line that runs from Washington to New York to Boston – and the country’s busiest and fastest passenger rail line. It carries only 3.4 million a year. Suddenly, that 13.5 million figure seems like it came out of dreamland.

And 41 million? As one letter in the Wall Street Journal pointed out, that’s 112,000 riders each day, or 4,680 an hour – every hour of every day.

Trouble is, they need all those riders to make the numbers work. Ahh, the numbers. Let’s take a quick look.

Voters more than a year ago approved more than $9 billion for the project. That sounds like a car load, but the HST needs $45 billion to get going. To help fill the gap, officials are hoping to get $10 billion-$12 billion of private investment or financing. But private money tends not to show up until the end, when the deal is about done.

That means we’re now depending on federal money. That $2.25 billion we just got from the feds? That was about half of what California sought this year. And it looks like there’ll only be a few dribs and drabs for high-speed rail coming from the feds in the next few years. HST officials say they need a total of $17 billion-$19 billion in federal money.

In short, the HST is shaping up as a good idea whose time has not yet come. With apologies to the Man in Black, I don’t hear the train a-comin’.