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Comment by throwaway0a5e | Hacker News Reader

Lowering speed limits doesn't do much except maybe in North Korea or somewhere else where draconian enforcement to actually get compliance is palatable. It's well understood in civil engineering circles that people in aggregate drive what they consider to be the reasonable speed for the road and if you want slower traffic you need to play visual tricks to make that happen. On multi-lane roads lowering speed limits makes things worse because it increases speed differentials between car traffic causing less predicable traffic flow (bad for pedestrians) and robbing drivers of situational awareness they could be spending on other things (like pedestrians). Changing out a bunch of signs is a feel good measure at best and a backhanded attempt to increase revenue via fines at worst.

If it was as easy as slapping up signs with low numbers and then reaping the political brownie points from reduced deaths every local politician would do it.

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I think the law is simply way too soft on this. If you're using heavy machinery in public areas, it should be absolutely mandatory that you follow the law, and are capable of doing so. People who either do not or cannot should simply not drive.

If somebody was driving a digger on a public street in a dangerous and unlawful manner, you'd expect them to end up in court, and you'd certainly expect more than just a fine and business-as-usual. A car is far faster and more dangerous than a digger.

Yeah. Drivers around here get irate at even the suggestion that they shouldn't be driving a minimum of 5 over on every road at all times.

> People who either do not or cannot should simply not drive.

I have the opposite attitude.

People who cannot use their own judgement as to what speed to drive or when a stop sign can be safely disregarded should not drive.

There are certain extremely predictable problems that occur when you allow people to use their own judgement to decide whether or not they need to follow rules/laws/etc., and I for one do not enjoy the outcomes of those problems.

How would you codify that into law?

I don't think you'd need to change much of the law.

A heck of a lot of stop signs would become yields. A heck of a lot red arrows would become blinking yellow arrows.

We could probably do automatic speed limits on limited access highways by measuring the current traffic speed, hitting it with some sort of weighted algorithm to prevent swings in speed or comically high/low speeds.

Frankly I'm surprised there's no such thing as a "yield, unless you're turning left or going straight" type stop sign since there are a lot of intersections where that's what the prevailing traffic flow is in practice.

A ton of intersections could be redesigned to facilitate easier and safer jaywalking with carefully placed islands.

If I had to change the law I'd have stiff fines for stopping at a cloverleaf and I'd make failing to go the minimum speed (which is usually the speed limit minus some constant) subject to the same fine schedule as speeding.

Did you not read they are redesigning streets to include bicycle lanes and more pedestrian areas thus narrowing and reducing natural speed.

Ubiquitous traffic cameras. Or perhaps GPS based speed limits (or speed warnings) if youre really concerned with fines.

In civil engineering circles, it is well understood that there are many measures that can reduce "natural" speeds, like "The number of street parking bays is being halved and ... Cycle lanes have increased and streets are being redesigned to make districts more pedestrian friendly," from the linked article.

I'm not sure how you got the wrong idea that this is "[c]hanging a bunch of signs," especially since HN guidelines suggest I assume you read the linked article.

Read between the lines.

If they were breaking out the heavy equipment and actually changing the infrastructure they would be trumpeting it as an infrastructure initiative, urban makeover/revitalization or something like that.

To assume that this is more than a simple regulatory change is to assume that the Paris government is wholly staffed with people too stupid to capitalize politically on a major infrastructure change.

They are messaging this as a regulatory change and talking about how they're adding bike lanes (already rolling out steadily for a long time as roads get repainted and resurfaced) and continued phase out of cars from the city center.

Nothing will change, because nothing is changing. All the stuff they're talking about is stuff they're already doing. They're just changing some signs in other parts of the city as well as though that's expected to change anything (which it's not).

Don't be so quick to read between the lines that you forget to read the lines!

You seem to be confusing a BBC News article based in large part on tweets with a prime messaging push by the government.

As the article points out, many cycling lanes have been introduced. The infrastructure has been changing, is changing, and will continue to be changed, as both supporters and critics alike attest.

Your original tweet suggested that putting up new signs would have no effect because people drive whatever speed they feel is safe. This is true, which means it's notable that critics point out the average speed in Paris is already below this new lower limit. So either the infrastructure changes have had a positive effect and now it's time for the limit to catch up, or the traffic is bad and it's time for the limit to catch up.

Either way, your pessimism seems to be unsupported by any of the supplied evidence.

speed is a poor proxy metric for injury/death, but it’s mediopolitically expedient and as such used regularly to misdirect conversation and policy. to reduce injury/death, we need to address distracted driving, reckless driving, and impaired driving. notice that all of these share ‘inattention’ in common. also note that it’s very hard to legislate attention, which is why the conversation gets misdirected toward speed.

however, there are measures like narrowing car lanes, adding street trees, and installing bike lanes that have positive effect on attention by making collision dangers more obvious (without making them more likely). these measures tend to also lower speed, but lowering speed shouldn’t be the primary goal, lest we implement more ineffective measures like speed limits and speed humps rather than the effective ones.

How is total energy in crash a poor proxy? Yes there need to be confunding factors for a collision to happen but halving speed (and it being easier to loose speed at low speed) should more than half the energy that goes into breaking bones.

Yes there are interventions you can do to cut collision likelyhood by more than 75% but "poor proxy is unjustified".

the point is that speed doesn’t cause the accident, only makes it more severe. it doesn’t change casualty rates materially. what we want to reduce is the accident in the first place, and reducing speed doesn’t do that, only increasing driver attentiveness does that. once we better solve the attentiveness issue should we consider severity and speed’s contribution to it.

They also need to have narrower lanes.

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