Hawaii island residents and officials are preparing for the potential cutoff of the main traffic artery should Mauna Loa spew lava across Saddle Road as expected in the next week.

Officially dubbed Daniel K. Inouye Highway, Saddle Road connects the windward and leeward sides of the island. Originally built by the Army during World War II to access military land at the saddle of Mauna Loa and Mauna Kea volcanos, Saddle Road is the shortest and most direct route between the island’s major population centers on opposite coasts.

Since Mauna Loa began erupting a week ago, volcano watchers have closely monitored the lava’s trajectory as it oozes downslope toward the critical state roadway. As of Sunday morning, just over two miles separated the road and lava, and the flow is advancing at about 40 feet an hour, according to Hawaii County Civil Defense.

If estimates hold, molten rock is expected to slather some portion of the road in about a week. But as is the nature of volcanos, things could change dramatically, and Saddle Road could be spared. If not, many routines will be disrupted.

Thousands of people traverse Saddle Road daily, including tourism and resort employees who live on the Hilo side and work at jobs on the Kona side. Other regulars include tradespeople, hospital workers, landscapers and truck drivers hauling food, fuel, waste and myriad forms of cargo.

Mattson Davis, owner of Magics Beach Grill in Kona, said he’s already heard from vendors who’ve told him to prepare for longer wait times for grocery deliveries because they’re anticipating having to take the Hawaii Belt Road to the north.

“I’m personally concerned about how it’s going to affect my pocketbook,” Davis said. “Will I get my supplies?”

The Belt Road hugs the Hamakua Coast from Hilo north to Honokaa and then juts west toward Waimea and down toward Kona. Workers commute from all over the island for shifts at resorts like Mauna Kea Beach, Mauna Lani, Westin Hapuna Beach, Waikoloa Beach, Four Seasons Resort Hualalai and others.

Saddle Road drivers can get from Hilo to Waikoloa in about an hour. It’s a smooth, paved road Davis described as “Hawaii’s Autobahn.”

If motorists have to take the Belt Road it could lengthen commutes because the Belt Road meanders through small communities with slower speed limits, traffic lights and crosswalks.

Kevin Hayashi is a golf professional who lives in Hilo and runs the Waikoloa Village Golf Club. He commutes five days a week on Saddle Road.

“That road is such a blessing,” Hayashi said. “It’s the best road on the island.”

Hayashi’s trying to stay positive and accept the fact that he might have to start driving the long way around. One thing he’ll miss if Saddle Road gets blocked is the highway’s wide shoulders and long, straightaways which add an element of safety.

The Belt Road is narrow and windy.

“If somebody starts veering off, there’s no place to go a lot of times,” he said.

On Thursday evening, Volcano resident J. Malia Buck had set up her tripod at dusk along Saddle Road and was settling in for an evening of lava gazing.

A semi-retired journalist originally from Maui, Buck routinely drives from Volcano to Kona via Saddle Road to shop at Costco, among other things. The prospect of having to take the longer route over the Belt Road has her rethinking her shopping patterns.

“I’m not going to spend six hours driving in the car for one hour at Costco,” Buck said.

Sean O’Phelan, a resident of Hawaiian Paradise Park south of Hilo, had stationed himself at a prime viewing area Thursday along Saddle Road across from the Mauna Kea Access Road.

If lava eventually covers Saddle Road, “it impacts the whole island,” he said.

Besides making it harder to reach Costco, west side beaches, and other amenities, O’Phelan worries about how working families would handle having to drive long distances to get to jobs. With soaring inflation, gas prices averaging $5.30 per gallon, and a staggering cost of living already, anything that adds more strain to a family budget is of concern.

“I worry about our community on both sides of the island,” he said.

The county’s mass transit administrator said he’s already made contingencies to shift the Hilo-Kona bus route that goes across Saddle Road to the Belt Road. It’ll be an express bus and should only add about 25 minutes to the route, said John Andoh.

How a major transportation bottleneck, like having the Saddle Road cut off, would play out for the island’s workforce remains to be seen. In what is already a tight labor market, some employers wonder whether extended commute times combined with high gas prices might make it even harder to find and retain good employees.

Craig Anderson, vice president of operations for Mauna Kea Resort, said he had felt a “little anxiety mixed with joy and glee” when he first saw the glow of Mauna Loa’s eruption from his home near Waimea.

Mauna Kea Resort employs about 1,200 workers and about 5% of those commute over from the Hilo side.

Despite the unknowns, Anderson is optimistic that even if Saddle Road gets shut down, it won’t be a huge blow for the resort industry.

“We think it’s an inconvenience but we’re not anticipating any major fallout,” Anderson said.

One upside of the volcanic eruption is a boost in inquiries and bookings the resort is experiencing from people wanting to come to the Big Island to see the lava up close, he said.

“For every call that we get from people concerned about their safety or air quality or flights or being run over by molten lava, for every one of those, there are probably 40 or 50 calls about, ‘What’s it look like?’ ‘This is exciting!’ Overwhelmingly, the interest is in wanting to experience it.”