The budget shortfall created by Boston's Big Dig is delaying replacement of a temporary vertical lift bridge between Weymouth, Mass., and Quincy, Mass., that some commuters believe to be unsafe. Drivers complain of rumbling and rattling in the temporary Fore River Bridge, which is scheduled for a $150 million permanent replacement in 2020. One nearby resident has collected dozens of rusty bolts from a park that lies under one end of the span. "Those plates are loose," he insists. "Something bad is going to happen."