3 ms·

Ah, one of my favourite correlation/causation mix-ups. Proving that increased speed is associated with an increased accident rate is not the same as proving th

Ah, one of my favourite correlation/causation mix-ups. Proving that increased speed is associated with an increased accident rate is not the same as proving that accidents are caused by speeding (and therefore 'accident rate could be reduced by slowing down'). Personally, I'm more inclined to think that dangerous drivers tend to speed more than safe drivers, hence the correlation, but in any case I'd love to see some evidence either way.

deleted 16y ago
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sprout 16y ago
Well, it's a simplification of a very complex system. I can think of at least one intersection where even going 40mph in a 35 zone will at least double your risk of a crash. I can think of other situations, for example highway driving, where going 80mph in a 65mph zone probably has an only minor effect compared to going 65mph, and depending on traffic could be safer.
CWuestefeld 16y ago
Yes, particularly in light of recent articles I've read describing improved safety as a result of increasing potential confusion (removing lane markers, etc.). The theory is that forcing people to pay attention, well, makes them pay more attention. I'd like to add another possibility beyond what you've noted. Might it be that speed isn't itself more dangerous in that it "causes" accidents, but when an accident occurs and higher velocity is involved, that means more kinetic energy is to be dissipated, and with all that energy in play, the results may be more dire? I'd also like to see more variables factored out of the data. I'd like to know about someone (like me) who observes other safety rules like seatbelts, proper lane discipline including signaling, safe following distances, etc.
- nitrogen 16y ago
  The theory is that forcing people to pay attention, well, makes them pay more attention. It seems to me that faster speeds may also force people to pay more attention, as each driving decision occurs in a shorter timespan. As for urban/suburban speeding, the risk factors (pedestrians, children, intersections) are completely different, and increased speeds would clearly increase risk, as well as slow overall traffic flow as fewer cars could successfully turn onto fast-moving streets.
brc 16y ago
It's not clear whether this applies to urban speeding or highway speeding. Urban speeding does increase accidents because of the large number of unexpected events in an urban setting (pedestrians, cars driving into intersections, etc). But the main issue I have with speed limit studies is that seem to make this underlying assumption that everyone follows them. If the core group of accident-causing people drive fast/drunk/etc regardless of the rules, then lowering limits/changing rules must have limited effect. Underlying all this is the government love of speeding taxes. The only problem is, the marginal return on speeding tax decreases as the tax take goes up. Because people decide to obey the limit, the tax take starts to go down. Thus the conundrum for governments - do they set the fines at a level where people are annoyed but don't mind, or do they increase the fines to the point where revenue steeply drops.
- cullenking 16y ago
  Two very good points. I speed like crazy on an open highway when on my motorcycle, but I accelerate very slow and stick to the speed limit when in the city. Too many bicyclists and pedestrians, not to mention intersections. Speeding on an empty and straight freeway has considerably less consequence. I definitely agree that the worst 20% of drivers create 80% of accidents (made up numbers), which makes most any speed limit conversation null and void.

deleted 16y ago

[deleted]

sprout 16y ago

Well, it's a simplification of a very complex system. I can think of at least one intersection where even going 40mph in a 35 zone will at least double your risk of a crash. I can think of other situations, for example highway driving, where going 80mph in a 65mph zone probably has an only minor effect compared to going 65mph, and depending on traffic could be safer.

CWuestefeld 16y ago

Yes, particularly in light of recent articles I've read describing improved safety as a result of increasing potential confusion (removing lane markers, etc.). The theory is that forcing people to pay attention, well, makes them pay more attention. I'd like to add another possibility beyond what you've noted. Might it be that speed isn't itself more dangerous in that it "causes" accidents, but when an accident occurs and higher velocity is involved, that means more kinetic energy is to be dissipated, and with all that energy in play, the results may be more dire? I'd also like to see more variables factored out of the data. I'd like to know about someone (like me) who observes other safety rules like seatbelts, proper lane discipline including signaling, safe following distances, etc.

nitrogen 16y ago
The theory is that forcing people to pay attention, well, makes them pay more attention. It seems to me that faster speeds may also force people to pay more attention, as each driving decision occurs in a shorter timespan. As for urban/suburban speeding, the risk factors (pedestrians, children, intersections) are completely different, and increased speeds would clearly increase risk, as well as slow overall traffic flow as fewer cars could successfully turn onto fast-moving streets.

brc 16y ago

It's not clear whether this applies to urban speeding or highway speeding. Urban speeding does increase accidents because of the large number of unexpected events in an urban setting (pedestrians, cars driving into intersections, etc). But the main issue I have with speed limit studies is that seem to make this underlying assumption that everyone follows them. If the core group of accident-causing people drive fast/drunk/etc regardless of the rules, then lowering limits/changing rules must have limited effect. Underlying all this is the government love of speeding taxes. The only problem is, the marginal return on speeding tax decreases as the tax take goes up. Because people decide to obey the limit, the tax take starts to go down. Thus the conundrum for governments - do they set the fines at a level where people are annoyed but don't mind, or do they increase the fines to the point where revenue steeply drops.

cullenking 16y ago
Two very good points. I speed like crazy on an open highway when on my motorcycle, but I accelerate very slow and stick to the speed limit when in the city. Too many bicyclists and pedestrians, not to mention intersections. Speeding on an empty and straight freeway has considerably less consequence. I definitely agree that the worst 20% of drivers create 80% of accidents (made up numbers), which makes most any speed limit conversation null and void.