4 ms·
I live in Norway. The most common highway speed is 80, but when you see someone driving sharp 80 it's most often a novice or the car is on automatic cruise. Mos
by varjag 3y ago
I live in Norway. The most common highway speed is 80, but when you see someone driving sharp 80 it's most often a novice or the car is on automatic cruise. Most people lay on 5-8 km/h but on a multi lane road people doing 90+ are not uncommon. Traffic cameras for 80 zones are typically tuned in +12.
I'm not sure where you are, but from my driving elsewhere, it appears similar in Sweden (only the posted speeds are higher), and worse in Spain & Italy.
And energy is quadratic with respect to velocity. Going 90->105 is worse than 30->45.
Since the speed delta is the same it's far worse with 30 to 45, and regulations reflect that.
- uxp8u61q 3y agoWe clearly have different experience on the road. > Since the speed delta is the same it's far worse with 30 to 45, and regulations reflect that. If E(v) = mv²/2, then E(v+dv) = m(v+dv)²/2 = mv² + m v dv/2 + m dv²/2. As you can see, the middle term is proportional to v, the initial speed. Kinetic energy does increase more going 90->105 than 30->45. Maybe this is too abstract, so he're a concrete example. Let's assume a vehicle weighing 1 ton (1000 kg). * Going 30 km/h => kinetic energy is 34 kJ * Going 45 km/h => kinetic energy is 78 kJ, so about 43 kJ more * Going 90 km/h => kinetic energy is 312 kJ * Going 105 km/h => kinetic energy is 425 kJ, so about 113 kJ more It's really basic physics.
- varjag 3y agoThen I think you understood that 15 over 30 represents more than a doubling of the energy versus the increase by 1/3 in the (already assuringly lethal for pedestrian) 90 case.