It can be a political statement, or it can be about noise and pedestrian safety, depending on the environment. Basically, it's irresponsible to drive faster th

It can be a political statement, or it can be about noise and pedestrian safety, depending on the environment. Basically, it's irresponsible to drive faster than 30 km/h anywhere with a significant number of pedestrians. The risk of serious injury and death rises quickly above that speed, and human drivers cannot react quickly enough at higher speeds. You can justify a bit higher speed limits on major streets with significant traffic, as pedestrians tend to be more attentive when crossing them. But even then, the limit should be 40-50 km/h, as road capacity decreases and noise level becomes unacceptably high at higher speeds.