If you want the short answer: the best urban bench for a busy sidewalk is usually a backless perch bench or a compact backless bench, not a deep park bench. People on busy sidewalks typically need to take weight off their feet for a minute or two, check a phone, or wait for a bus. A simple seat lets them do that without blocking the walking path.
I’d look for a seat height around 17 to 19 inches. That makes sitting down and standing up easy for most adults. A seat depth of 12 to 16 inches is enough for perching, but not so deep that people slide back and stay for a long time. A slight slope on the seat helps rainwater drain and discourages sleeping.
Materials matter because sidewalks are tough. Powder-coated steel or aluminum frames with wood or aluminum slats are low-maintenance and handle weather, skateboard wear, and heavy daily use. Avoid cheap plastic, untreated timber, or solid metal seats that get extremely hot in summer.
Size and placement are just as important as the bench itself. For a busy sidewalk, a compact bench around 24 to 36 inches wide works well. Keep at least 4 to 6 feet of clear space beside it for pedestrians, strollers, and wheelchairs. Place it near a storefront, tree, bus stop, or building edge, not in the middle of the walking flow.
If you need to prevent people from lying down, choose a model with a center armrest or a gently contoured seat. Otherwise, keep it simple. Most street furniture gets over-engineered, but a sturdy bolt-down backless bench is usually the smartest choice. It gives people a quick, dignified place to rest without turning the sidewalk into a lounge.