In a bizarre sight Thursday night, San Diego police pulled over a group of two dozen motorcyclists en masse on Interstate 15 north of Mission Valley, a traffic stop that shut down the northbound side of the freeway. It started about 10:30 p.m., when officers tried to pull over a group of 24 motorcyclists for multiple traffic violations on the freeway near Aero Drive, San Diego police said. Police said the riders initially failed to stop but when they finally did, they didn’t pull over to the shoulder — they stopped on the freeway, blocking a lane of traffic. That led authorities to close the freeway, and extra officers arrived to assist. The traffic stop led to three arrests, police said, including for a felony warrant and weapons-related offenses.