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I think there's a fundamental issue here that the posted speed limit is often not the same thing as a reasonable maximum speed that's appropriate for conditions

by toast0 2y ago

I think there's a fundamental issue here that the posted speed limit is often not the same thing as a reasonable maximum speed that's appropriate for conditions. Speed limits are set for all sorts of reasons that don't often match up with safety, and even then, they're usually set for normal conditions; when you have great visibility, dry pavement, and low traffic, it's often not unsafe to exceed the posted limit; just the same as when there's poor visibility, wet or icy pavement, or heavy traffic, following the posted limit is unsafe. Having an alarm that distracts the driver when they're driving a safe and reasonable speed is an unnecessary distraction. And it won't help drivers maintain a safe and reasonable speed in unfavorable conditions, unless this also comes with real time updates for pavement conditions, visibility, construction, etc. For cars that have trouble exceeding the speed limit, it can be dangerous --- sometimes there are scenarios where exceeding the speed limit is the safest course of action; but experience with the vehicle would help you anticipate its capabilities, and it is what it is. Usually there's pretty clear feedback that the vehicle isn't going to go much faster, so you will tend to avoid putting yourself in situations where you need lots of speed. Rental trucks governors aren't necessarily as obvious, but that's also more of a statement that trucks should have a lower maximum limit regardless of conditions and that the rental company doesn't trust renters to be aware of safe speeds for trucks.

stoneman24 2y ago
There is also many places where there are extremely few posted speed signs. The A9 in Scotland from Perth to Inverness is a notoriously dangerous road (it has large sections of single carriageway [60mph] with occasional dual carriage [70mph]). It has many junctions where cars can cross lanes to leave on minor roads. So bad, it has a large system of average speed cameras to hopefully control the traffic. Driving slowly (40-50) on this long road will cause cars, buses and trucks to try and overtake even on the single carriageway sections which is risky for everybody. But very few actual speed signs, so you end confused and wondering exactly what is the correct value for that section and anxious about the next average speed camera. And that’s for experienced uk drivers, I hate to think how stressed the tourists are ?
dangus 2y ago
I'm confused at your argument. You're talking about inclement conditions where you're supposed to be driving below the speed limit anyway. If everyone is at or below the speed limit, there is no situation where the reasonable maximum that exceeds the speed limit. Perhaps you could safely drive faster, but nobody actually has to drive faster. And when you're driving slower your stopping distance is less, your chance of death in an accident is less. It's basic physics and accident statistics.
- toast0 2y ago
  > And when you're driving slower your stopping distance is less, your chance of death in an accident is less. It's basic physics and accident statistics. The faster we travel, the less time we spend traveling. The posted limit is not necessarily a reasonable maximum speed; that's my point in both directions.
  - dangus 2y ago
    The math does not work that way. If you’re going 70mph you travel 16.6% further in the same amount of time. But your average stopping distance increases 240 to 315 feet, 31% increase. This also stresses your reaction time. Risk of severe injury in pedestrian accidents goes like this: 16mph: 10% 23mph: 25% 31mph: 50% So if you slow down in a pedestrian heavy area from 31mph to 23mph, you travel 30% slower but if you hit someone you’ve cut the chance of seriously injuring them in half. https://www.rac.co.uk/drive/advice/learning-to-drive/stopping-distances/ https://www.rac.co.uk/drive/advice/learning-to-drive/stoppin... https://aaafoundation.org/impact-speed-pedestrians-risk-severe-injury-death/ https://aaafoundation.org/impact-speed-pedestrians-risk-seve...
    - toast0 2y ago
      Is your position that motor vehicles should be limited to 16 mph? I don't disagree that a reasonable and appropriate maximum speed in a pedestrian heavy area is lower than a reasonable and appropriate maximum speed on a restricted highway. But, I've seen pedestrian heavy areas with posted speed limits above a reasonable and appropriate speed, and restricted highways with posted speed limits below a reasonable and appropriate speed. A system that annoys and distracts the driver and other occupants when the vehicle is traveling above the posted speed limit does not help safety when the posted limit is unreasonably high or unreasonably low. It could possibly help if the posted limit is reasonable and the posted limit is detected correctly. It doesn't seem reasonable to me to mandate a system like this when advisory detection systems have poor accuracy and posted limits are commonly set based on criteria other than the safety of road users.

by toast0 2y ago

stoneman24 2y ago

There is also many places where there are extremely few posted speed signs. The A9 in Scotland from Perth to Inverness is a notoriously dangerous road (it has large sections of single carriageway [60mph] with occasional dual carriage [70mph]). It has many junctions where cars can cross lanes to leave on minor roads. So bad, it has a large system of average speed cameras to hopefully control the traffic. Driving slowly (40-50) on this long road will cause cars, buses and trucks to try and overtake even on the single carriageway sections which is risky for everybody. But very few actual speed signs, so you end confused and wondering exactly what is the correct value for that section and anxious about the next average speed camera. And that’s for experienced uk drivers, I hate to think how stressed the tourists are ?

dangus 2y ago

I'm confused at your argument. You're talking about inclement conditions where you're supposed to be driving below the speed limit anyway. If everyone is at or below the speed limit, there is no situation where the reasonable maximum that exceeds the speed limit. Perhaps you could safely drive faster, but nobody actually has to drive faster. And when you're driving slower your stopping distance is less, your chance of death in an accident is less. It's basic physics and accident statistics.

toast0 2y ago
> And when you're driving slower your stopping distance is less, your chance of death in an accident is less. It's basic physics and accident statistics. The faster we travel, the less time we spend traveling. The posted limit is not necessarily a reasonable maximum speed; that's my point in both directions.
- dangus 2y ago
  The math does not work that way. If you’re going 70mph you travel 16.6% further in the same amount of time. But your average stopping distance increases 240 to 315 feet, 31% increase. This also stresses your reaction time. Risk of severe injury in pedestrian accidents goes like this: 16mph: 10% 23mph: 25% 31mph: 50% So if you slow down in a pedestrian heavy area from 31mph to 23mph, you travel 30% slower but if you hit someone you’ve cut the chance of seriously injuring them in half. https://www.rac.co.uk/drive/advice/learning-to-drive/stopping-distances/ https://www.rac.co.uk/drive/advice/learning-to-drive/stoppin... https://aaafoundation.org/impact-speed-pedestrians-risk-severe-injury-death/ https://aaafoundation.org/impact-speed-pedestrians-risk-seve...
  - toast0 2y ago
    Is your position that motor vehicles should be limited to 16 mph? I don't disagree that a reasonable and appropriate maximum speed in a pedestrian heavy area is lower than a reasonable and appropriate maximum speed on a restricted highway. But, I've seen pedestrian heavy areas with posted speed limits above a reasonable and appropriate speed, and restricted highways with posted speed limits below a reasonable and appropriate speed. A system that annoys and distracts the driver and other occupants when the vehicle is traveling above the posted speed limit does not help safety when the posted limit is unreasonably high or unreasonably low. It could possibly help if the posted limit is reasonable and the posted limit is detected correctly. It doesn't seem reasonable to me to mandate a system like this when advisory detection systems have poor accuracy and posted limits are commonly set based on criteria other than the safety of road users.