Have you ever thought about why cars are designed the way they are and driving is how it is? Well, we’ve got some more answers for you.

As our vehicles moved on from the humble horse and cart to faster mechanically propelled ones and in much greater volumes, we started to introduce a series of rules. These rules have to work for us as driver and people. So why are most maximum speed limits worldwide nearly always 70 mph (113 kph) or thereabouts?

people in the far distance

Besides the physics of it that says the faster you go the more room you need to stop safely, what does 70 mph limit give us? The 100-meter stopping distance is about as far as you can still see a person’s face. This means we can react to another person and we would also know that they have seen us. Hopefully, they would be getting out of our way now or we would have a chance to stop without killing them.

This ability to see a person’s face at 100 meters gives us street lamps just under 100 meters apart. At night time if you are walking, you want to be able to have some idea of the people walking around you.

30 mph speed limit

The 30 mph speed limit is in place so that in the unlikely event that your car hits a person they have just over 50% chance of survival. If you drop the speed down to 20 mph that becomes 95%. This illustrates how our bodies react to speeds and impacts from cars.


Stay tuned for more on how our bodies shaped driving.