SAN FRANCISCO (CBS SF) — When BART began transporting passengers 45 years ago, it was a modern marvel. But now, entering middle age it’s unique design and construction have combined to create challenges.

It was 45 years ago Monday that the massive transit system opened for business.

“It very definitely had a future feel, it was during the aerospace age,” said BART Operations General Manager Paul Oversier of the system’s sleek passenger cars.

Mike Healy, the system’s first spokesman, watched a tape of his KPIX 5 interview on opening day.

“We have about 5,000 people coming through up till noon, now that’s the count we have at this point,” he said during the 1972 interview.

He laughed at the fashion of the day and his facial hair.

“That’s me with the mustache, and that’s Carl Gustav, King of Sweden,” he said of the interview. “You know, BART was a phenomenon. It was the new, modern space age transportation system.”

The cars design was considered futuristic on opening day.

“It really was,” said Randy Rentschler of the Metropolitan Transportation Commission. “It was almost a fetish for rockets, and planes, and they put that fetish on a train, and that’s resulted in one of the most unique designs in the entire world.”

But the uniqueness that made BART sexy in the 1970s now has created challenges.

“BART is a one off system, there’s no question about it,” Oversier said. “The fact that no other transit system in the United States chose to follow our wide gauge.”

Rentschler agrees.

“It’s built into the system, the train is a lightweight system, the cars are unique, the wheels are unique, the power system is unique,” he said.

It is the same story behind the notoriously long escalator repairs. They were built by German company that has gone out of business making the replacement parts almost impossible to find and often have to be custom fabricated.

Then there is the 19 miles of track without a buypass lane. One small problem can cause big delays

“A 4 minute delay will probably mean 15-20 minute late trains,” Oversier said.

And the stations that often become overcrowded.

“The stations aren’t big enough,” Rentschler said. “The Embarcadero station where we are now, simply can’t handle the capacity that’s being asked of it.”

So as it turns 45, the once train of the future is struggling to carry the weight of the present.