CNN
 — 

As the world’s largest active volcano spews molten rock in Hawaii, the lava flow is inching closer to a major highway that serves as the shortest route between east and west sides of the Big Island.

Over the past day, the lava’s advance from Mauna Loa slowed to an average rate of about 40 feet per hour, but the lava flow has remained active since the volcano first erupted days ago.

The flow front was about 2.4 miles from the Daniel K. Inouye Highway as of Saturday afternoon, according to the US Geological Survey.

The highway remains open and has attracted sightseers who have flocked to the area for the spectacular lava show – though it has created heavy traffic congestion on the highway.

If the lava crosses the highway, it could add hours to residents’ commutes by forcing alternate routes and create “a tremendous inconvenience,” Hawaii Gov. David Ige told CNN Saturday.

“That is the main connection between East and West Hawaii. Very, very high volumes of traffic,” Ige said. “If in fact the lava was to overrun the highway, then people would add half an hour to an hour and a half depending on where they’re getting to, to their commute time.”

Experts on Thursday said the earliest the lava could reach the highway would be in about a week if it continues at its current pace – but stressed that the lava flow remains unpredictable.

“There are many variables at play and both the direction and timing of flow advances are expected to change over periods of hours to days, making it difficult to estimate when or if the flow will impact Daniel K. Inouye Highway,” USGS notes in its latest update.

Still, if lava does cover the roadway and makes it impassable, commuters and delivery companies are in for a hassle.

Emmanuel Carrasco Escalante, a landscape worker, said he would have to decide between the north side or south side coastal roadways to get from Hilo to Kona.

“It’s a hassle to drive all the way around the island,” he told CNN. “If the road closes, that would add almost two hours, more gas, and more miles so hopefully it (lava) doesn’t cross that road.”

And though the lava’s path remains unpredictable, the transportation department will be able to provide a six-hour notice of the road’s closure, authorities said.

“And the staff at the Hawaiian Volcano Observatory say that they can provide at least 24-48 hours advance warning if the lava appears to be threatening the roadway,” said Adam Weintraub, communication director for the Hawaii Emergency Management Agency.

If emergencies arise during a possible highway closure, there are hospitals and first responders on each side of the island, Weintraub said.

Talmadge Magno, administrator of the Hawaii County Civil Defense Agency, said authorities will work with shipping companies to make adjustments to limit cross-Island traffic.

“It’s a full community effort that’s going to take to come together if Daniel K. Inouye Highway is taken out,” Magno said.

As the rivers of molten rock ooze down towards the highway, authorities say the lava poses no immediate threat to any homes.

The volcano began erupting late last Sunday night, springing back to life for the first time since 1984.

But the eruption was no surprise, said Ken Hon, scientist-in-charge of the Hawaiian Volcano Observatory.

“It has been showing signs of rumbling … since mid-September,” said Hon. “We saw a rapid inflation or filling of the summit in the last two weeks of September, accompanied by large swaths of earthquakes.”

What has been unpredictable is how the lava would flow. Advance rates will continue to be “highly variable” over the next weeks, USGS noted Saturday.

The lava was initially oozing down steep slopes, but the flow from one of the fissures has since reached flatter ground and slowed significantly, according to USGS. Three other fissures are no longer active.

Still, it’s dangerous situation on the ground.

“The lava spewing forth is thousands of degrees centigrade and it really is a dangerous situation. And the eruption is unpredictable,” the governor told CNN.

Mauna Loa’s summit is about 21 miles west of Kilauea, a smaller volcano that has been erupting since last year. The two simultaneous eruptions have created a rare dual-eruption event, according to Hawai’i Volcanoes National Park.

“It is an awe-inspiring sight. There’s nothing else like it,” Ige said.