Thirty-five Philadelphia-area high school students and chaperones were hurt after their charter bus slammed into a low-hanging overpass on Soldiers Field Road in Allston Saturday night.
Massachusetts State Police said the crash happened when the driver, 66-year-old Samuel J. Jackson of Philadelphia, attempted to pass under the Western Avenue Bridge around 7:30 p.m.
A preliminary investigation shows that Jackson did not see the warning sign indicating the height of the bridge, and that the bus was not supposed to be on the road. Ray Talmedge, owner of the Philadelphia-based Calvary Coach Bus company, told WCAU-TV that Jackson looked down at his GPS and saw the bridge when he looked up but it was too late to avoid hitting it.
At least three of the 35 passengers taken to Boston-area hospitals may have suffered serious injuries, according to police.
The charter bus was on its way back to Pennsylvania following a day trip to Harvard University.
Several passengers were trapped inside the bus for about an hour after the accident. The Boston Fire Department had to extract passengers from the mangled roof of the bus.
The last victim was freed from the bus around 9 p.m.
A collision reconstruction team cleared the scene Saturday night, but that report could take up to six weeks to complete.
The bridge was due to for rehabilitation next year, according to MassDOT Spokeswoman Sara Lavoie.
"Our inspectors were to scene last night determined the bridge was structurally sound. This bridge is due for rehabilitation next year as part of the accelerated Bridge program," Lavoie said.
A spokeswoman for the Department of Recreation and Conservation, which owns the roadway, said Sunday that Soldier's Field Road is one of many historic parkways along the Charles River that are not meant for heavy traffic.
"They were meant to take a lovely Sunday drive along the park or the Charles. They were not mean to be thoroughfares," said S.J. Port, a DCR spokeswoman.
Port said that there are "redundant" warning signs on the roadway, and that it is "a little early to talk about plans" to add more.
"There is concern over an uptick in GPS use," she said, adding that most of the incidents involving large vehicles on the roadways are due to people who rent box trucks - like moving trucks.
Investigators are looking into how long Jackson was behind the wheel. There are federal regulations as to how many hours someone can drive in a given time period. As of this afternoon he was not arrested, nor was he given a citation.
The National Transportation Safety Board may come to Boston to assist in the investigation, but police were unable to confirm that as of deadline.
The plan Saturday night was to hoist the bus over a nearby guardrail, but when that failed, police removed a section of the guardrail to get the buss off Soldiers Field Road. The guardrail was repaired today.
There was no structural damage, but there was some cosmetic damage to the bridge and roadway.
Storrow Drive was closed in both directions from Western Avenue to Charles Circle for several hours following the crash.
Follow Morgan Rousseau on Twitter for updates: @MetroMorgan