Like millions of other Americans on Tuesday evening, Nancy Backus spent a quiet evening at home, monitoring the results of the general election.

As Auburn’s mayor and as a member of the Sound Transit Board, however, Backus had a particularly keen interest in one measure — ST3, Sound Transit’s ambitious, $53.8 billion plan to add more light rail and more transit buses in King, Pierce and Snohomish counties by 2044.

A measure its opponents derided as too expensive and predicted would ultimately prove ineffective at solving the region’s traffic agglutination.

But from 8 p.m. to 8:45 p.m, a computer glitch at King County Elections kept the results in King from hundreds of thousands of eyeballs glued to computer screens throughout the three-county area, including Backus’s.

And in that interval, all that could be said about ST3 was that Pierce County was thumping it by a convincing margin of 55.53 percent to 44.47 percent.

But when early election returns from King finally rolled in and showed ST3 winning, (likewise in Snohomish County), Backus could finally breathe a bit easier.

“It looks like it is going to pass. I think that the people in this region have taken a historic action to build a true, regional mass transit system. And you know, that’s what we’ve talked about for decades,” Backus said.

Here are the updated results for ST3 in the three counties, as reported by the Secretary of State’s webpage at 3.53 p.m. Wednesday.

Approve: 54.8 percent, (446,875 votes)

Reject: 45.2 percent (368,622 votes)

Breaking the results down for each county yields the following:

King: 58.35 percent approve (323,113 votes) to 41.65 percent reject (230,658 votes)

Snohomish: 51.58 percent approve (55,544 votes) to 48.42 percent reject (52,133 votes).

Pierce: 44.28 percent approve (68,218 votes) to 55.72 percent reject (85,831 votes).

Should the results survive the trickling in of additional votes in the coming days, its framers say ST3 will complete a 116-mile regional system, five times larger than that of today, reaching Everett, Tacoma, the Seattle neighborhoods of Ballard and West Seattle, and new Eastside destinations of Redmond, south Kirkland, Bellevue and central Issaquah.

According to Sound Transit, the estimated cost to implement ST3 is $53.8 billion in year-of-expenditure dollars, of which $27.7 billion is to be financed with new local taxes.

ST3 would accomplish this by increasing the following local taxes:

• Sales tax by 0.5 percent, or 50 cents on a $100 purchase;

• License tabs by a motor vehicle excise tax increase of 0.8 percent, or $80 annually on a $10,000 vehicle;

• And property taxes by 25 cents for each $1,000 of assessed valuation, or $100 annually for a house assessed at $400,000.

On the “what-do-we-get-for-our-money,” side, the plan describes, among other things, 62 miles of light rail and stations serving 37 new areas to the north, south, east and west of today’s light rail route. And allowing existing bus routes, now caught in congestion, to run on freeway shoulders, where possible.