San Diego’s much-maligned transit system is in the process of implementing a series of upgrades.

The trolley’s blue line, the most successful leg of the existing network, is heading toward final approval of an extension that would allow a rider to head from University City, through downtown San Diego, to the U.S.-Mexico border without a transfer.

And construction is now under way on a high-frequency bus line called bus rapid transit, or BRT, that’ll connect SDSU and the mid-city neighborhoods, Chula Vista and Escondido to downtown San Diego. It’s meant to have similar service levels to a rail system, at a fraction of the cost.

As those changes get under way, here’s a look at San Diego’s existing transit system in a national context.

Let’s start with a ranking from the American Public Transportation Association, a national advocacy group for public transportation, of the 25 cities with the most “unlinked passenger trips” on public transportation. That’s the number of times a resident boards public transit, without counting transfers as additional trips.

It’s a blunt measure of how many times people decided to use transit, but it also ends up giving a high ranking to large cities, like Los Angeles, without accounting for how many residents there never use public transportation.

San Diego ranks 14th, just after Denver and ahead of Minneapolis.

San Diego does a little bit better if you rank those same cities by passenger miles, rather than total boardings.

But these raw measurements of transit trips or transit miles traveled leave a major elephant in the room: Not many people use public transit as a primary means of transportation.

Here’s a chart showing how people in San Diego get to work. Public transportation accounts for all modes besides taxis.

How does that measly blue slice, accounting for 4.1 percent of the working population, or roughly 25,700 people, stack up with other large cities?

Not very well.

Here are the same 25 cities we looked at before, ranked by the share of the city’s population that commutes via public transit, according to the U.S. Census Bureau.

These numbers refer to the population of each specific city, not the overall metro area. The previous two top 25 lists ranked overall metro areas.

San Diego comes in second to last, ahead of just Phoenix, by this measurement.

That means there aren’t many people in San Diego who’ve been able to exchange their car payment, gas expenditures, time spent in traffic and any repairs for daily usage of the public transportation system.

Correction: An earlier version of this post said construction was set to begin on a bus rapid transit line. Construction got under way in July.

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