Here are some best practices for sidewalk closures published by the city of Oakland, California. In a nutshell, contractors have to provide a walkway rather than make pedestrians cross the street in downtown areas, expect for very short periods. The walkways have to be ADA accessible. If the walkways take up a bike lane, there has to be a safe place for the bikes to go. Barriers have to be substantial enough to actually protect pedestrians if vehicles hit them. I could walk 5 minutes in any direction in Philadelphia and see every one of these principles violated.