Wales lowers speed limit to 20 mph to cut car use and save lives
Wales lowers speed limit to 20 mph to cut car use and save lives
The Welsh parliament has passed a law bringing down the speed limit on all residential roads and busy streets to 20 mph (30 km/h). Not everyone is pleased.
cross-posted from: https://beehaw.org/post/7658487
For more detailed information: https://www.gov.wales/introducing-20mph-speed-limits-frequently-asked-questions
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Wouldn't this, in the end, make cars have to shift to a lower gear, thus keeping about the same RPM, and thus eating about the same amount of fuel, which results in about the same volume of the sound produced by the car?
This feels like a terrible fix.
afaik most of the sound comes from the tires, not necessarily the engine or the exhaust. obviously not the case for every car, but for most commuter cars it is. the faster the tires are rolling, the louder the sound.
i think at higher speeds the wheel and road noise drowns out the engine noise, but at lower speeds its the engine, especially during acceletation.
in the region of 20-30mph i'd think the engine is probably the louder part.
While this is a point the naysayers brought up, the slower speeds during the trial period reduced accidents, the severity of accidents, and the slower speeds encouraged more foot and bicycle traffic on those roads
Do you know when the trial period was?
I ask because the Welsh government apparently carried out a pollution test to justify the lowered speed limit on the main road into the capital, but did it during the Covid lockdown, when most cars were off the road.
Most cars, at least in NA, have excessively large engines. It is crazy that we use 2L engines to carry one person around, when their own legs would suffice.
Wouldn’t this, in the end, make cars have to shift to a lower gear, thus keeping about the same RPM, and thus eating about the same amount of fuel
That's not how cars work, they definitely don't use the same fuel in different gears at the same RPM. See this Wikipedia article for a discussion of speed vs fuel economy.
And as pointed out by the the FAQ, that's doesn't not factor in acceleration:
Will driving at 20mph mean I use more fuel?
No. Fuel consumption is mainly influenced by the way we drive – driving at a consistent speed is better than stopping and starting. Accelerating up to 30mph can take twice as much energy as speeding up to 20mph.
A default 20 mph limit and a smooth driving style, can help avoid unnecessary speeding up and slowing down, saving fuel.
Studies have been done on this, and lower speeds correspond with less noise pollution.
https://www.sciencedirect.com/science/article/pii/S0160412022005785
A lot of cars can cruise at 20-25mph just idling in Drive, foot completely off both gas and brake. The RPMs don't get much lower than that.
My forester, when the engine is cold, will idle at about 25 mph :v, it calms down once it's warm, but still. I wouldn't be driving around with my foot on the brake
if the cars are designed to use the same fuel for less useful output power, then they're very badly designed.
i'm sure they might be less efficient in terms of miles per gallon. but they surely can't be so bad as to waste absolutely more fuel at lower speeds.if they are, fuck them.
People have a misconception that cars waste more fuel at lower speeds, but it's really due to where the lower speeds are happening. Fuel is mostly wasted due to constant stopping and acceleration, like in a city environment with traffic lights and stop signs. On a highway, it's actually more efficient because you aren't stopping so often.