>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.
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.