[Sephiroth]

Originally Posted by spiderplant

It's true. Let's do some sums...

I'll use metric to keep it simple, but feel free to convert to whatever units you prefer.

Firstly, 30mph (48km/h). Now I'm sure you're a sensible driver, and always leave a safe gap from the car in front so you can stop if necessary. The Highway Code tells me the typical stopping distance at that speed is 23m. And let's say a typical car is 4m long. So each car at 30mph occupies 27m of road. So each hour, 48000/27 cars can travel along the road. That's 1778 cars per hour.

Now 20mph (32km/h). The stopping distance is 12m, and cars are still 4m long, so each car occupies 16m of road. Each hour, 32000/16 cars pass. That's 2000 cars per hour.

So by reducing speed from 30 to 20mph, you've managed to get 12% more traffic down the same road.

..... Until they reach a junction or roundabout. You'll only get the increase in throughput on an open road with right of way priority.