Safe speeds are not whatever speed is comfortable to drive a given street. Part of the posted limit is considering how much of a wrecking ball a vehicle would be if it suddenly left the road.

The limits in suburbs where I live is 50km/h. The roads are wide enough to land a plane on and you could very easily drive most of them full throttle as they are flat and straight. With that in mind I still think it should be 30km/h.

When I was a kid a car hit a snowbank and was launched straight into someone's living room not far from my house. If they were driving 30km/h, that nightmare scenario pretty much becomes an impossibility.

We just need to stop making residential roads that look like drag strips. More curves, more trees close to the road, more speed bumps. I've driven in some places in Europe where it's very clear that it's unsafe to drive any faster than about 30 km/h due to roadside obstacles. I think that design is much safer than the NA standards.

As a bicyclist and pedestrian, many roads are above safe levels. Others it's well below. Tbh it's all arbitrary