[sliverstorm]

Reducing speeds is a form of collision prevention, is it not? A typical car can just about stop on a dime at 15mph, and a pedestrian has more time to react.

There's a whole slew of other pedestrian-friendly street design that we could & should adopt as well, but that doesn't make speed any less of a valid approach.

[hermitdev]

Speed, in of itself, is not dangerous. What is more dangerous on highways is differential speed. i.e. if you're driving 60 mph when the traffic around you is doing 80 mph, you're the problem. Probably exponentially so if you're driving slowly in the "fast" lane. While rarely enforced, most states in the US have laws that require you to pull to the right if you're impeding traffic (usually defined as holding up +2 vehicles behind you) - even if you're doing the speed limit. Yet, these laws are rarely enforced, just like "No Trucks Left 2 Lanes" is never enforced in & around Chicago, despite being posted every mile or so on I 294.

I'd wager, also, that speed itself is rarely the direct cause of an accident. High speed, though, will make an accident more severe. My bet is that distracted driving is the #1 cause of accidents. On my daily 2-hour round trip on Chicagoland highways, I usually see 4-6 accidents each involving >2 cars. The shear amount of people I see on their phones is staggering. Hard to tell if it's social media or texting, but you can always tell because their head is staring at their lap, or they're holding their phones at the top of the steering wheel for all to see. I also see people with their phones mounted on their dashes watching movies or TV shows. Playing with your phone while driving is far more dangerous than paying attention & speeding.

[lsc]

>What is more dangerous on highways is differential speed.

That sounds like an extraordinary statement to me, by which I mean that you need to support it.

First, let me make a distinction between crashes where drivers lose control after the collision, either due to shock to the driver or damage to the car, and crashes where they don't. In the latter case, I agree with you; a freeway scrape where both cars can slow in a controlled manner is probably pretty safe. And you are more likely to have that sort of accident when you are going at similar speeds in the same direction. But it's not a certain thing;

Cars are complex systems, and designed to operate without colliding with other vehicles. Cars are also much more likely to lose control when they are operating closer to their speed design envelope.

However, in the case where either the car or the driver is incapable of continuing to control the vehicle, at that point the car continues to hit other things until it's stopped (and is often hit then by traffic that isn't stopped.) At that point, total speed matters a lot.

There is just a whole lot more energy involved when you are moving fast than when you are moving slowly, and when energy is dispersed in an uncontrolled manner near people, those people tend to get hurt.

[sliverstorm]

Speed, in of itself, is not dangerous

Certainly! Falling from great height isn't dangerous either, you know.

[thomastjeffery]

Reducing speeds in some places makes sense, but in county roads out in the country, it just creates a reason for bottleneck, which clumps traffic together, making collisions more likely.

For example, a 4-lane road that I drive on to get to the city will usually have two cars in the front driving practically the same speed, and slower than the traffic behind them. To fix this situation, the car on the left should speed up and get over, so that traffic can flow around it and spread out. Unfortunately, there is so much educational focus and enforcement on speed limits that the driver on the left believes [s]he is driving correctly.

[sliverstorm]

Naturally, a lone country road designed for speed is fine. It's when you've got a high speed road with lots of on-street parking and pedestrians right next to traffic, even house fronts, where you've got a major clash of functionalities and a safety problem.