Im familiar with these crossings. Long trains are dropping off or picking up at the port - Dole imports come in there, but also some chemical/fuel tanks i think mostly bound for the navy shipyard. Shunting always causes the long train to go back and forth between the convention center and petco park, obstructing at least 2 level crossings, although pedestrians can take the mentioned foot bridge. Freight traffic is restricted to the evenings, due to the many level crossings and shared tracks, including single track portions, with Amtrak and the local COASTER commuter train from san diego union station all the way to orange county

This is one of the reasons to always take transit to DTSD rather then driving a car.