> safely

But is it? A 20/25mph speed limit implies a residential street. If you are doing 40 could you stop in time if a kid is hidden by parked cars and suddenly runs out into the street chasing a ball? If not, could you scrub off enough speed quickly enough to get below the ~20mph threshold where a collision with a pedestrian is unlikely to be fatal?

This is a function of the road design. We know based on studies that most folks drive the speed they feel comfortable regardless of the posted speed limits. I live right across the street from a school. It’s naturally a 25mph zone. But the roads are literally as wide as a highway road with perfect sight lines and bike lanes on both sides. It’s a very straight and wide path with clear visibility for about a mile so of course cars are going to fly down that road regardless of the posted limit.

All it would take is some traffic calming measures on each side of the school zone. Chicanes or bollards which narrow the road and force people to slow down and been demonstrated to be highly effective at regulating speed. Roads should be designed for the speeds that motorists are meant to travel if safety is an actual goal.

Yes, that illustrates my point. Road calming doesn't make the road less safe, but drivers slow down because it feels less safe. In other words, drivers don't have a great feel for what speed is actually safe.

> It’s so incredibly frustrating going 20 or 25mph on a road where most drivers could easily safely drive over double that.

It's the minority of drivers that should worry you. Speed limits and road safety aren't only for the ideal conditions and safest drivers. And they aren't just for what drivers feel safe doing but what everyone else is safe with.

Very conservatively and in ideal conditions, at 50mph it takes at least 10m to decide to act, another 10m for your foot to get the signal, and another 30-40m to stop. NHTSA estimates between 260ft-300ft. Do you still think most drivers can safely drive in an urban/residential environment with 60-100m stopping distance?

You say "most drivers could easily safely drive", I say "most drivers dangerously overestimate their ability" and are only prepared for best case scenarios. The rules are for all those other cases. A better option would be to make the road the limiting factor and not just via a rule. Drivers feeling less safe at higher speeds would bring that in line with what other participants to traffic feel and make everyone safer.

> I say "most drivers dangerously overestimate their ability"

I say "most road users dangerously overestimate their ability". At 10mph (about 16 km/h) most bikers dangerously overestimate their ability to safely turn, brake or handle road bumps without invading other lanes, crashing or falling from their bikes.

A bike doesn’t weigh over a ton though, while understandable that some bikers ride rather aggressively their ability to maneuver effectively at speed is far better than a car.

> A bike doesn’t weigh over a ton though

being hit by a bike that broke my leg I would say that bikes having no crumple zones (the opposite is true actually) are not without risks for pedestrians

> their ability to maneuver effectively at speed is far better than a car

I guess that's because biking is a conscious choice, not something you have to do, there aren't hundred millions bikes constantly around on the streets, so usually average bikers are better than the average driver

but having 4 wheels and a differential makes maneuvering effectively at speed much easier than on 2 (very thin) wheels

also the thing is you don't have to stop a car to avoid accidents, ABS and a steering wheel can go a long way.

I think people focus too much on breaking space, reaction times and all of that, but if you see an obstacle and can turn away from it without rolling to the floor or worse, you're 95% done.

two car crashing or hitting a wall with a car is far better than hitting a person.

most of the hit-n-runs happen because the driver pushes the brakes too hard, the wheels block, the car loses directionality and hits straight the pedestrian.

of course lowering speed limits is the easiest choice, you crunch the numbers, at 30km/h there's 50% chances less of a a fatal crash than at 40 km/h, so it seems like the obvious choice, but that also mean that the best choice is no cars at all

In Italy, my country, the average speed for cars in Milan is 9.1 km/h, in Rome is 8.5 in Naples 7.3, hardly high speed.

most of the hit-n-runs are people crossing the streets at night, with low visibility hit by cars that greatly exceed the speed limits, DUIs incidents, old people at the wheel that ran a red light and things like that.

most of the deaths are people literally ran over by the car, not just hit

there are cases of people killed by cars going in reverse, so at very low speed

the point is the drivers mindset should be that speed control happens at the gas pedal, not at the breaking pedal

breaking shouldn't be #1 emergency measure, avoiding the obstacle should, and then brake

how many road users have attempted to pass the moose test? with their car, bike, motorbike, whatever?

how many of them have developed the right mentality for "maneuvering effectively at speed" instead of just doing it without realizing that everything has always gone well until now because luck exists?

> I also often see sections of road with speed limits well below what the road can handle, where EVERYONE is speeding, cops included.

You say "cops included", as if cops speeding was otherwise unusual; it very much is not, and never has been.