Niesha Brown is expecting to see less of her 5-year-old son. Arthur Arschin is counting on getting less sleep. Cary Dicken is taking a wait-and-see approach.

The Long Islanders are among the 600,000 rail passengers who use Penn Station daily — and who will be affected by extensive track repairs that will partly shut down the nation’s busiest train hub for nearly two months starting Monday.

Transportation officials are relying on a web of alternatives to move the masses — from express buses and ferries to diverting trains to other subway-linked terminals. Even work on key roads and bridges serving Manhattan was finished ahead of time as demanded by Gov. Andrew Cuomo.

Nonetheless, officials are urging the commuting public to stick with mass transit and not drive, to keep from creating massive traffic backups.

But despite the options and reassurances, riders are anxious about what lies ahead. That was evident Saturday at Penn.

Brown, 44, a geriatrics registered nurse from Uniondale, is prepared to wake up earlier and get home later.

advertisement | advertise on newsday

She works a 7 a.m. to 7 p.m. shift at NYU Langone Medical Center in Manhattan and dreads how the transit mess may add 45 minutes to her commute each way.

“My plan is to take the LIRR into Jamaica and subway from there,” she said. “Or drive, which I totally hate — during rush hour.”

Arschin, 65, of Jericho, an attorney with a practice in Manhattan, is going to change the time on his alarm clock.

“I’m definitely gonna have to wake up early,” he said of his plan to catch a train out of Hicksville. He intends to avoid the brunt of the evening commute by staying longer at the office.

“I usually leave late,” he said, “but I’m gonna leave later.”

Dicken, 39, a fertility doctor from Port Washington, is trying to stay flexible about getting into Manhattan.

“I’m gonna ride it out. I don’t really have another option,” she said. “ . . . See how it goes next week and make adjustments as necessary.”

During the repair work, LIRR service will be reduced by 20 percent between 6 and 10 a.m. and 4 and 8 p.m., officials said. The railroad will run extra off-peak trains, lengthen trains with additional cars, reroute trains to stations where riders can transfer for free to subways, and provide ferries and express coach buses at no additional cost.

To help prevent traffic jams, tow trucks and maintenance crews will be pre-positioned on major highways, said Ron Epstein, assistant commissioner with the state Department of Transportation.

Temporary ferry service will debut Monday morning from Glen Cove, and about 200 express buses will be deployed at park-and-ride lots, officials said. An additional seven lots have been added, including one at Bethpage State Park.

advertisement | advertise on newsday

While the Penn repairs technically began this weekend, they will last until just before Labor Day — on Friday, Sept. 1.

How will all this play out? State officials aren’t making predictions, but they will be watching closely.

The “war room” is in place, Epstein said Friday.

“Every day, both in the morning and the p.m., we will see what works and needs to be adjusted. We will modify accordingly,” he said.

The state transportation department and the Metropolitan Tranportation Authority will be reacting in real time, Epstein said, keeping motorists informed if bus or ferry lots are full and directing them to other options. LIRR riders will be notified of service changes via social media, websites and printed bulletins, or “seat drops,” distributed on trains.

advertisement | advertise on newsday

Not every chokepoint could be fixed in time after Amtrak’s April announcement — following a series of fiercely criticized outages — that Penn’s maintenance couldn’t be delayed any longer.

Still, a good number were. A cashless tolling system at the Verrazano-Narrows Bridge was installed ahead of schedule, along with upgrades at the Robert F. Kennedy Bridge and the Queens Midtown and Hugh L. Carey tunnels.

The state will make only emergency road repairs during the day, restricting other projects to the night, Epstein said.

New York City put a weekday “construction embargo” on Manhattan roads that commuters will need to navigate, though it ends on Aug. 1, a city transportation official said.

Along with the Port Authority’s Bayonne Bridge, the Verrazano joins the RFK Bridge, Henry Hudson Bridge, Carey and Midtown tunnels, Cross Bay Bridge and Marine Parkway Bridge in eliminating the need to stop and pay a toll.

On Long Island, the two ferries that will carry passengers to Wall Street and 34th Street in Manhattan have made test runs to the Glen Cove ferry terminal.

Uniondale-based RXR Glen Isle Partners is working this weekend to finish about 265 ferry parking spaces at a waterfront development it is building, to add to 108 existing terminal parking spaces.

With David Olson and Matthew Chayes