EDITORIAL THE SUBSTANDARD SUBWAY THE MTA IS JUST DISCOVERING THAT COMMUTERS ARE HUMAN BEINGS.

THE planning geniuses at the Metropolitan Transportation Authority have made two very startling discoveries about Angelenos:

We drive cars, and we need bathrooms.

Somehow, when designing L.A.'s infamous $45.5 billion subway, MTA officials overlooked these phenomena. In a rare effort at cost-cutting, in arguably the biggest waste of money in the history of American public works projects, they decided to skimp on potties and parking lots. They installed none of the former, and too few of the latter.

It's as if even MTA officials themselves believed nobody would actually ride a subway to nowhere. But with a mandate to build and billions of dollars at their disposal, they plodded along with the construction anyway.

Never actually imagining that real human beings might someday ride the subway, they dispensed with real human conveniences.

But now that the subway is up and running - and clogged freeways have scared a modest number of commuters into riding it - these deficiencies have made themselves clear.

At the MTA's North Hollywood station, the 847-car lot often fills up before 9 a.m. on weekdays. When commuters are unable to find a parking spot, they're forced to circle around the neighborhood in a desperate search for available street parking.

We don't even want to guess what they do when they can't find a restroom.

Better late than never, the MTA is now addressing these problems.

To ease the parking crunch, it proposes adding room for 356 more cars by building a supplemental lot in North Hollywood and expanding capacity by restriping the existing NoHo and Universal Studios lots.

And to facilitate the commuters' hygiene, the MTA has sold an advertising firm the rights to an estimated $50 million in billboard space. In exchange, the MTA gets 10 percent of the ad revenues and 10 new, self- cleaning restrooms. Never mind that if you do the math, that comes to about $4 million a toilet - for the MTA, this is progress.

So now the L.A. Subway is finally bringing its amenities up to speed, we offer another suggestion: How about a functional fare-collection system?

Currently, the subway has no turnstiles, which makes paying the fare optional - an option that, if we had to guess, plenty of riders decline.

The result is the MTA probably is flushing away as much cash on its lost fares as it is on its overpriced commodes.

MTA officials report that ridership is up. But with no way to count nonpaying passengers, how would they know?

Probably by looking at the overcrowded parking lots.