> they drive the speed they feel comfortable with, regardless of the speed limit
My anecdata does not support this. When roads are not congested, I can see that most drivers accelerate from ~70+mph to ~80+mph right ofter the speed limit sign changes from 60 to 70.
> Opponents of speed limits often claim that the majority of people do not regularly drive faster than 130 km/h, ... If we look at the data, however, the picture is quite different.
Did you read the link I posted? Theres lots of empirical data out there that says that drivers drive the same speed on a road, regardless of the posted limit. That speed is based on their judgment of the road - sight lines, shoulder width, sharpness of curves, etc.
How is that any different than someone who goes 100MPH and then 20MPH and claims to have not violated a 65MPH rule because the average speed was 60MPH for the trip?
The units of the measurement do not dictate how the measurement is made.
>most people drive roughly 5 miles per hour over the speed limit>speed limit does in fact have a mitigating effect.
You got the causality dangerously backwards. That's not how policy works.
"The speed limit is commonly set at or below the 85th percentile operating speed (being the speed which no more than 15% of traffic exceeds),", as per [1].
Specifically, speed limits are not set by carefully measuring & modeling conditions on the road by direct application of science; there's no finely tuned measuring aparatus nor advanced math model. Instead we rely on drivers judgement aggregated over time, conditions, and locations. Granted, there are certain notable exceptions: bridges & tunnels where speed limit is also informed by structural constraints, and also fuel consumption reduction policy in cases like the 1973 speed limit.
And yes there are natural parallels to civil disobedience; in some cases limits got raised or lowered upon public pressure.
> It’s a standard practice in traffic engineering to set limits based on 85th percentile speed of free flowing traffic in good conditions. That apparently tends to produce an optimal speed limit from a crash/mortality perspective, but has the side effect of criminalizing the conduct of 15 percent of motorists.
No, it doesn't, for several reasons, most notably:
(1) percentiles don't work that way; particularly, if everyone who would drive at or faster than the limit in its absence drove exactly at the limit in its presence, it would have no effect on the 85th percentile speed, so setting and maintaining an 85th percentile limit doesn't require any violations of the limit to occur,
(2) simple speed limit violations often are not criminal in and of themselves, so even if 15% were driving over the limit, they wouldn't be criminals.
I'd argue that it's almost never correct to drive the speed limit. In the US at least they are almost universally slower than the natural speed of the road by 5-10 mph and everyone speeds a bit all the time.
Yes, and I directly addressed it's points. Did you read my post? Because you don't seem to address what I've said, and you ignore that I've more directly dealt with the points made in the article than you do in yours.
> 85% of people drive at a safe speed regardless of what the speed limit is.
No, traffic engineers have come to the conclusion that, because speed variance is a significant source of risk, the safest speed limit (considering auto vs. auto issues only) is the 85th percentile speed of traffic on the road, which (at least with patterns of enforcement over the time the rule was found and since) seems not to vary much based on posted limits, in any case.
That's? the 85th percentile rule, and it's the single most common rule for setting speed limits in the US. Its incorporated in federal guidance, its incorporated in most state laws (though with some exceptions—e.g., school zones, upper highway speed limits—in virtually all of them).
Given that the 85th percentile speed will rarely fall on exactly a convenient numbee, you'd expect nearly half of limits to be below that because of rounding, and add in some conditions which create downward departures in limited cases, and, sure, as the article body says, most (>50%) are below. But that's not the headline's "every speed limit".
Not is it clear, as I stated previously, that the 85th percentile rule is ideal for safety for mixed use. There's considerable global evidence that lower speed limits are better for that.
> In England at least the speed limit is the absolute maximum speed at which you drive.
In theory this may be true but it's absolutely not in practice. It's not uncommon to see people at least 20mph over the limit on motorways. On the M4 that is practically the norm.
> That's one possible interpretation, mine would be that people will always speed slightly above the posted limit because they know the odds of being ticketed are small
Data doesn't back you up. In places where they have raised the speed limit, the overall flow speed does not increase correspondingly.
People drive at the speed they deem safe irrespective of the speed limit.
There are outliers in any group. Nobody is debating that. All we’re saying is roads tend to have a speed where the vast majority of drivers are comfortable and they’ll tend to go that fast.
Most times you’re on a road and traffic is flowing significantly faster than the posted limit, either the limit is wrong or the road is poorly designed and not fit for purpose. And that happens a lot in the US.
I think you have a fundamental misunderstanding about how people drive. People don't look at a speed limit and then drive 15 over; they drive the speed they feel comfortable with, regardless of the speed limit. Studies have shown this:
Q. Wouldn’t everyone drive faster if the speed limit was raised?
A. No, the majority of drivers will not go faster than what they feel is comfortable and safe regardless of the speed limit. For example,
an 18-month study following an increase in the speed limit along the New York Thruway from 55 to 65 mph, determined that the average
speed of traffic, 68 mph, remained the same. Even a national study conducted by Federal Highway Administration also concluded
that raising or lowering the speed limit had practically no effect on actual travel speeds
If speed limits aren't set based on a real world survey of organic driving speeds on a given road segment then they are 100% arbitrary. In the vast majority of the U.S. it's just a number that a bureaucrat picks for any number of reasons that aren't related to actual safety.
Anyone complaining about speeding on this thread needs to spend some time reading up on the available research. For example, on the highway the drivers with the lowest accident rate tend to go 10mph over the limit. There are many more findings along these lines that should piss off any safe driver that likes to go at an appropriate speed for their own vehicle/reflexes/conditions.
In my experience, most people drive roughly 5 miles per hour over the speed limit. That suggests to me that the speed limit does in fact have a mitigating effect.
If you look at the studies, they actually show this. There is a small percentage of drivers (something like 5-15%) that always try to drive at the speed limit, even if that is lower than the speed they would naturally drive at.
This is one of the reasons experts argue that you NEED to set the speed limit at the natural speed people will drive at; otherwise, you will have a big speed difference between the majority who drive at the comfortable, faster, speed, and the 15% who are driving slower at the speed limit. You want the two groups to drive at the same speed.
The author seems to acknowledge but then ignore how their strict adherence to the speed limit makes roads less safe overall.
The author is doing something that the rest of the drivers don’t expect, which is increasing speed differential by driving at unexpectedly slow speeds. The author is causing more danger by not following accepted cultural behaviors.
The culturally accepted speed is also 5-10 mph above the speed limit and not exactly at it, because that’s the maximum speed you can drive before risking a ticket.
The design of the road itself often dictates the speed at which people feel comfortable:
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