Quote:
Originally Posted by TorqueDog
The speed is already there. The data does not show that raising a speed limit to match traffic speeds simply shifts the entire distribution upward and preserves the same variance at a higher speed. What it shows is that when a limit better matches prevailing behaviour, the differential drops.
People who already felt safe at 120 were already there, they don't suddenly decide 130 feels fine because a sign changed. Meanwhile, a chunk of the 100-110 crowd does move up toward the flow, which narrows the spread. That reduction in speed differential is what lowers conflict between vehicles due to constant lane changes, tailgating, risky passing, and so on. One of the key takeaways from the Solomon Curve research is that crash involvement rises as a vehicle's speed deviates from the mean traffic speed, both above and below it. The outliers who ignore conditions exist regardless of the posted limit (ie: the typical RAM pickup driver), and that's an enforcement and licensing problem, to be sure -- but it's not a speed limit problem.
I agree wholeheartedly that infrastructure, access management (friggin' level crossings), and licensing (see: anyone with an O-plate and an Uber decal) need improvement, you'll get nothing but agreement from me there. But that's not an argument against aligning limits with reality... it is an argument for doing both. Waiting for perfect infrastructure before fixing a misaligned speed limit just means continuing to engineer unnecessary speed differentials in the meantime. Edge cases and bad drivers are exactly why you don't set limits based on worst-case behaviour.
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I believe the data actually does show that the variance can increase, though usually small, more often than it decreases. I don’t think your position is really evidence based. Here’s an example of a study that suggests the opposite:
https://www.wisdomlib.org/science/jo...oc1774242.html
The “feels safe” argument doesn’t really do a good job of explaining the majority of behaviour. For one, if someone is going 120 in a 110, that may because it feels safe. It may also be because they’ve determined it to be a speed at which they are unlikely to get a ticket. Because traffic plays such a big role in “what feels safe,” if more people are suddenly going to go 120 instead of 110 (even though they determined for the same reasons that 110 was the speed for them, they’ll suddenly change their mind I guess), then going 130 will feel roughly the same as 120 did, so there’s little reason to stop people who were already speeding to speed even more.
But even if your argument were evidence based or some studies did show that, what almost all studies also show is a significant increase in crashes and, more importantly, fatal crashes. And even in the few older studies where crashes didn’t increase a lot, they did increased a lot around entires and exits. So it very much is a case where the infrastructure needs to come first. Otherwise all you’re doing is advocating killing more people so that you can drive to Edmonton 5 minutes faster. That sounds dramatic but it is the reality of the situation.