A fierce struggle over automation has erupted at the Port of Los Angeles, as local union officials representing some 12,000 dockworkers demand that one of the world’s largest shipping firms abandon a plan to introduce driverless electric cargo trucks.

Shouting, whistling and jeering, more than 1,200 union members, local business owners and community activists packed a four-hour hearing Thursday before the Los Angeles Board of Harbor Commissioners. The board voted to postpone a construction permit for the automated system after an offer by Mayor Eric Garcetti to mediate the dispute.