They just lowered it in Paris to 30km/h. Lower speed is directly correlated with less crashes. The other benefit is less noise, which is very important in an urban area. In most urban areas now the loudest most constant noise is from vehicles.

50KPH is the norm in any built up area, including in housing estates. Like a subdivision. That's 30mph, for a place where kids play in the green, cats dart out between parked cars, and there's tons of ped traffic.