Comment by wpm
5 days ago
You don’t need to be either.
Suppose a trip is 5km.
At 50km/h, that trip takes 6 minutes.
At 30km/h, that trip takes 10 minutes.
In practice, this naive way of calculating this doesn’t even reflect reality, because odds are the average speed of a driver through Helsinki was around 30km/h anyways. Going 50km/h between red lights doesn’t actually make your trip faster.
> Going 50km/h between red lights doesn’t actually make your trip faster
Except when it does, due to horrible traffic engineering practices.
There were a pair of one-way streets in the downtown of my city. Both attempted to have "green wave" setups for the lights. One worked pretty well, the other was okay, but whatever.
The problem was that the road itself was signed at 30 mph, but the lights were timed at 40 mph. It literally encouraged people to speed if it were not too busy (e.g., after business hours).
I saw the reverse once. Some town in the (US) Midwest when I was a kid. Downtown had signs that said "The traffic lights are synced for 25 MPH". It wasn't a speed limit, just a statement. When you figured out that they were telling the truth, you started driving 25.
That would be sensible.
If I'm being very charitable, I would say you might naively set this up so that the next light's stopped traffic clears just before the previous light's traffic arrives, and perhaps that's how it worked during the day (I was a teen, I didn't go downtown during business hours much). After 5, it just encouraged you to punch it to make them all in one go.
> In practice, this naive way of calculating this doesn’t even reflect reality, because odds are the average speed of a driver through Helsinki was around 30km/h anyways. Going 50km/h between red lights doesn’t actually make your trip faster.
This is a wonderful explanation.
Though I've lived in Europe (Düsseldorf and London), my default sense of urban density is still American so it was hard to fathom such a low potential average speed. In London, I didn't bother with a car.
I'm not an advocate for speeding in the cities, but this example is really bad - it says my trip time will be extended by 66%! For a really short one, it doesn't matter, but when you drive 40 minutes initially, it's really unacceptable for most.