Pileup on I-5

Beams in the middle of the tunnel help reinforce concrete girders running across the top. More than two dozen vehicles crashed and burned in the southbound truck tunnel Oct. 12, 2007, leaving it heavily damaged. (Al Seib / Los Angeles Times)

Sept. 16, 2014 2:58 AM PT

OCT. 14, 2007: The charred remains of commercial vehicles south of the I-5 tunnel under the transition roads for the I-5 and Highway 14 in Santa Clarita. (Genaro Molina / Los Angeles Times)

PROBE: CHP officers were on the scene Sunday, Oct. 14, 2007, to investigate the crash. (Genaro Molina / Los Angeles Times)

DAMAGE: CHP Sgt. T.W. Lackey stands against a fire ravaged wall on the north end of the I-5 tunnel Oct. 14, 2007. (Genaro Molina / Los Angeles Times)

Caltrans and contractor staff inspect the tunnel’s interior walls, where sections of concrete have peeled away and exposed steel reinforcement bars. (Al Seib / Los Angeles Times)

Engineers mark core samples taken from the tunnel walls that were examined to determine the level of damage. (Al Seib / Los Angeles Times)

In the days following the pileup, a 55-mph speed limit was posted along I-5 southbound for all vehicles. Typically, the speed limit for trucks is 55 mph; for cars, it’s 65 mph. (Al Seib / Los Angeles Times)

It’s standing room only for commuters including Beth Maxwell, left, on a Metrolink train that left the Lancaster Station at 5:10 a.m. Monday, Oct. 15, 2007, bound for Union Station downtown. Regular riders reported that there were more passengers than usual. Still, “it’s not the crowd we had anticipated,” said Denise Tyrrell, press relations representative with Metrolink. “We think the crisis may have passed.” (Genaro Molina / Los Angeles Times)

Commuters file into Union Station in downtown Los Angeles hours after Interstate 5 was reopened. Transit officials added more trains to commuter routes from the north. (Robert Gauthier / Los Angeles Times)