The Army yesterday apologized for the huge traffic gridlock created with Tuesday's overpass accident, but did not give many details about what happened, citing an ongoing investigation.

Maj. Gen. Stephen Tom, deputy commander of U.S. Army, Pacific, at Fort Shafter, said "it is with deep regret that this accident ... has affected all the families throughout the City and County of Honolulu."

The military transport truck that hit the pedestrian walkway was hauling a hydraulic excavator from Pearl Harbor back to Schofield Barracks after it was used in the demolition of an old barracks on Kwajalein Atoll in the Marshall Islands, Tom said during a news conference.

"It is a travel and transit they had made previously," Tom said. But for reasons still unexplained, the boom of the excavator was at a height of about 18 feet — higher than in previous transports — which resulted in it striking the overpass, he said.

Tom did not want to speculate about whether the truck was riding too high or if the boom could have been lowered.

Asked if the transport truck clipped several signs on the way from Pearl Harbor, Tom said he had heard such a report, but couldn't confirm it.

Tom also said he believed a permit was needed from the state Department of Transportation for the movement, but acknowledged one was not applied for.

Asked why not, he said that it's part of an ongoing Army investigation to determine what caused the accident, and if the driver will face punishment.

The Army is conducting an Article 15-6 investigation, which is more than an administrative review and theoretically could lead to a court-martial offense, but in this case likely will not, said Lt. Col. John C. Williams, a spokesman for U.S. Army, Pacific.

The 35-year-old transport driver, a sergeant, has been suspended from driving, the Army said. The soldier has 12 years of civilian experience driving oversized vehicles, and has been driving such vehicles for five years in the Army, his company commander said.

The truck was operated by the driver and an assistant, also an enlisted soldier.

Army officials yesterday said the transport truck was traveling without its usual front and rear escort vehicles, but later said that, too, is under investigation.

"We know what (the driver) told us, we know what other folks have told us," but the investigation has to determine what really happened, Williams said.

Capt. Jonathan Johnston, who commands the 82nd Engineer Company, said four oversize vehicle transport missions have been carried out since October, and the excavator was transported with a permit and lead and trail vehicles.

Col. Stanley Tunstall, deputy commander of the 8th Sustainment Command, said he was not aware of any pressure placed on the driver to move the equipment to Schofield faster than normal.

Tom said the investigation will determine liability and fault, but he stopped short of saying the Army would pay for the walkway damage.

"What I want to tell everyone is that the Army is a responsible member of the community, and we'll do the responsible thing," he said.

Reach William Cole at wcole@honoluluadvertiser.com.