New Year’s Day marks the launch of what might be considered the broadcasting equivalent of Boston’s Big Dig.

At 3 a.m. on Sunday, NBC will flip the switch on NBC Boston, a newly launched O&O that will broadcast via a patchwork quilt of signals from three stations serving the nation’s ninth-largest TV market. NBC has been planning to shift the affiliation in Boston from its 22-year incumbent, Sunbeam Television-owned WHDH, to the new station for the past year.

The move is a gamble for NBCUniversal and parent company Comcast, which is the dominant cable provider in the market. The shuffle from a strong station to a startup threatens to dent NBC’s national ratings, at least until Beantown viewers figure out where to find “Today,” “The Tonight Show,” “Sunday Night Football,” “Saturday Night Live” and other signature shows.

NBC Boston, whose call letters are WBTS, faces the additional marketing challenge of not being able to promote a single channel number to viewers. Because the signal will be beamed out via three different stations, the channel number for over-the-air reception will vary depending on where viewers live. NBC Boston will be found at either 8.1 or 60.5 in the greater Boston area, or 60.2 for those in northeastern Massachusetts and southern New Hampshire. On the region’s major MVPDs, however (Comcast, Verizon, DirecTV, and Dish), NBC Boston will be found at a single designated channel near its largest rivals in the broadcast cluster.

NBCUniversal is counting on the appeal of its signature shows — notably “Sunday Night Football,” “The Voice” and buzzy newcomer “This Is Us” — to prompt viewers to surf around to find the station. The fate of NBC Boston will serve as a test of the power of digital signals, online navigational tools and programming brands to draw a crowd compared to the traditional TV muscle of a broadcast signal that easily penetrates a market. Boston has about 2.4 million television households, which represent about 2.1% of total U.S. TV households.

“Our first mission is to make sure people can find us,” said Mike St. Peter, president of NBC Boston, New England Cable News and Telemundo Boston. NBCU has mounted a marketing blitz that included everything from transit ads to spots on Pandora to dispatching its news anchor teams with food trucks to hand out hot chocolate and scones at busy shopping areas during the holidays.

To create NBC Boston, NBCUniversal acquired a digital low-power station to serve as the core signal in the market, even though it doesn’t have the same reach as its ABC, CBS or Fox rivals. But NBCUniversal already owned a New Hampshire-based Telemundo affiliate, WNEU, that serves the Boston market. WNEU will devote one of its digital multicast signals to simulcast NBC Boston, boosting the channel’s availability. But that still wasn’t enough to cover the market, so NBCU in December struck a deal to lease more digital simulcast space on another small station, WMFP in Lawrence, Mass.

NBCUniversal has poured money into building out NBC Boston’s news operation and assembling state-of-the-art weather forecasting resources — it is New England in the wintertime, after all. The station has the benefit of drawing on the resources of Comcast’s established New England Cable News channel, the largest regional news operation in the country. NECN, NBC Boston, and Telemundo Boston will share newsgathering resources and studio facilities.

“This is a big sports town and a big news town,” St. Peter said. “We have assembled a great team with lots of experience in this market. There’s a lot of news viewing [in Boston] and viewers expect a high standard of coverage.”

WHDH, meanwhile, is also amping up its local news operation. In place of network programming, the station will add newscasts at 9 p.m. and 10 p.m. Syndicated programs, including “Family Feud,” will help fill in other gaps. Paul Magnes, VP and general manager of WHDH, said they’ve been encouraged by the performance of a recently launched 7 p.m. newscast.

“A few years ago people would have said a 7 p.m. news would have been a crazy idea,” Magnes said. “But with the way people watch TV now with so much of primetime being watched on DVR, having more news turned out to be a terrific thing for us. We’re hoping this is the perfect time for us to invest more in local news.”

WHDH generally ranks No. 1 or No. 2 in Boston in key news time periods, vying for supremacy with the Hearst-owned ABC affiliate WCVB and the Cox-owned Fox affiliate WFXT. With the switch, it will jump from seven and a half hours of local news per day to 12 hours. WHDH will control all of the ad inventory in those local newscasts, unlike with network-provided programming, which could be a boon to the station if ratings are strong.

NBCU’s moves in Boston buck the tradition of networks seeking to avoid market affiliation shuffles at all costs. But old-school deference to incumbent affiliates is fading as distribution platforms proliferate. CBS made a switch in Indianapolis two years ago after failing to come to financial terms on a new deal with its longtime incumbent. Networks are driving hard bargains in seeking payments from affiliates in exchange for providing network programming. For decades, before the competitive landscape exploded, it was the networks that forked over compensation payments to affiliates for carrying their shows.

One local TV veteran unaffiliated with NBC or WHDH asserted that NBC Boston’s unconventional signal plan was something no network would have accepted from a third-party station owner. The executive likened it to Boston’s famed Big Dig highway and tunnel project that took more than 15 years and $15 billion to complete.

WHDH filed a lawsuit in federal court last March seeking to stop the NBC affiliation switch. Sunbeam argued that Comcast was using its clout in the market to force a disruption that would make it harder for Bostonians to find NBC programming without paying for cable or another MVPD provider. The suit asserted that Comcast’s real motive was to strengthen its cable business and consolidate market share in Boston, where Comcast also operates the regional Comcast Sports Network.

The suit was dismissed by a judge in May.

The NBC Boston station and related website have been featuring a countdown clock promoting the switchover since Nov. 10. On New Year’s Eve, WHDH will carry the NBC network’s programming hosted by Carson Daly from Times Square, while NBC Boston will offer six and a half hours of live coverage of Boston’s First Night celebration from Copley Square. That coverage, to be simulcast on NECN and Telemundo Boston, will be hosted by NBC’s Boston’s primary news anchors, Phil Lipof and Shannon Mulaire, and tubthump the switchover with segments planned featuring Jimmy Fallon, “NBC Nightly News” anchor Lester Holt and “Today’s” Matt Lauer and Savannah Guthrie.

At 3 a.m., the station will carry a rerun of the last two and half hours of the First Night celebration. The first NBC Boston newscast will air from 5:30 a.m. until 8 a.m., when the weekend edition of “Today” kicks in. Later in the day, NBC Boston will carry an NHL game and, of course, “Sunday Night Football” in primetime.

The arrival of NBC Boston promises to raise the tempo of the broadcast TV competition, particularly in local news, public affairs and lifestyle programming. WHDH’s Magnes said he’s seen more image-burnishing moves by rival stations in preparation for the shakeup on Jan. 1.

“There’s only so many ratings points available, and so many eyeballs available,” he said. “It’ll be interesting to see how the landscape shifts.”