Seventeen people were injured, some seriously, when a pickup truck collided with a trolley in Chula Vista late Tuesday afternoon, authorities said. The crash happened about 4:30 p.m. when the truck broadsided a northbound Blue Line trolley at the L Street grade crossing, Metropolitan Transit Service spokesman Mark Olson said. Three of the injured people suffered major trauma in the crash, Chula Vista Fire Capt. Eric Martinez said. It’s not clear what led the pickup to crash into the side of the trolley. Olson said MTS is investigating and “will provide further details when the investigation is complete.” Trolley service is closed between the H Street Trolley Station to the Iris Avenue Transit Center, three stops to the south in Otay Mesa. Olson said the transit agency is providing bus shuttles to serve the stations affected by the closure. He said Blue Line passengers should expect delays into Wednesday morning.