In the 46 years since its first train rolled, BART has been a pioneer of technical innovation.

It had the first automatic train control system when it opened. It had the first automatic fare vending. The Transbay Tube was the first submerged tube for transit.

As the line extends from Berryessa through downtown San Jose, BART should embrace another first in the nation: A single-bore tunnel, with trains entering stations one above the other instead of side by side under Santa Clara Street.

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The Valley Transportation Authority is all in. So is the city of San Jose — its professional staff as well as Mayor Sam Liccardo and the city council.

But to qualify for federal funding, BART has to agree. While the VTA will build the tunnel, as it did the tracks to Berryessa, and will pay maintenance and operating costs, BART employees will operate the line. And BART is dubious of the single tunnel. It’s more comfortable to keep it the same as the rest of the system.

We’re confident BART’s staff and board will rise to the occasion. This is the future of tunneling technology, and BART, for all its flaws in maintenance and other areas, has not shied away from innovation.

The large, single bore will go deeper than side-by-side tunnels, avoiding utilities. The technology has been used for years for water delivery and such, but only recently has it been scaled to handle transit. It might be less expensive. It will definitely take less time to build.

The main plus for San Jose is that the deeper single tunnel would avoid massive disruption of downtown during five years of construction — no small advantage for a blighted urban core just now catching a wave of market demand.

The old cut-and-cover construction for stations would mean having three blocks of the city’s main east-west street, Santa Clara, from Market to Third, fully ripped up for the greater part of five years. The single-tunnel stations are smaller. Vents and such would have to be installed, but it would be no different from routine utility repairs in the street.

BART dismisses the five-year disruption as short-term. But that’s like insisting on using a big incision to remove your gall bladder instead of having laparoscopic surgery. You can survive both, but why opt for more pain?

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Mercury News editorial: BART to San Jose brings good news BART’s concerns include safety of evacuation in case of a disaster, but VTA engineers are confident these can be answered. The other major concern is that the system would require more training for operators. No question there, but that shouldn’t be an impediment to better technology.

Barcelona is the world pioneer for single-tunnel systems. It works great. And it’s safe. Other American cities are looking at single-bore for future construction, after years of “big dig” projects going bad. BART surely will look at it for its next transbay tube.

It can go first in Silicon Valley, where the world looks to innovation.