Right, but also imagine how traffic would be if everyone drove with the pre-requisite distance to do that. Can you imagine I-5 traffic if everyone had 10 car lengths between them?
So while your statement isn't wrong, it's also not always pragmatic in the real world.
Of course it's pragmatic. Free-flowing traffic at 50mph beats people zooming up to 70mph then braking, then zooming again. Freeflowing traffic at 50mph annihilates traffic from accidents.
Traffic is rarely “free flowing” at any speed on these kinds of roads. Often I see “moving roadblocks”: clumps of cars going around or just under the speed limit jockeying around each other, impeding other traffic from moving around them. So-called “defensive drivers” are often unpredictably overly cautious: I’d wager they are at least an indirect cause of accidents quite often, but are severely under-represented in the statistics (if/when they’re represented at all).
> Often I see “moving roadblocks”: clumps of cars going around or just under the speed limit jockeying around each other, impeding other traffic from moving around them.
Indeed - this is the 70mph is slower than 50mph thing I mention.
Not sure if we’re talking about the same thing. These slower drivers aren’t any safer: they’re weaving around each other and impeding faster traffic from passing. They’re arguably more dangerous because of that. And the flow of traffic is constrained to the speed they choose, which is on average slower than it otherwise would be.
Most traffic is not caused by sheer volume - this is well studied. It is often caused by inability to maneuver, merge, etc. As a result, your i-5 traffic would likely be much much better if everyone left 10 car lengths.
You do not have to raise the average speed of travel very much to make up the theoretical loss due to increased spacing
Can you link to those studies about traffic? I’m aware of some of the studies regarding merging (eg the benefits of zipper merging) but I don’t think that covers the bulk of congestion.
This is why cars do not scale: by the time traffic slows down there are 5-6 times more cars in the lane than it can safely handle. So by the time people are asking for "one more lane" they really mean 6 times as many lanes, a regular 4 lane highway needs 20 more lanes!
I don't know what I-5 traffic is like, and kind of weird that you would refer to a local road on a global forum, but I'll assume it's like the M25.
Roads like that are currently operating at bursting point. There are incidents and accidents every single day and constant police presence is required to unblock them. If you alleviate congestion, more people use the road. They just go back to bursting point. In other words, it's utterly insane.
Can you imagine if there were accidents on railways or in the air every day? Imagine the scandal if train operators were found to be unsafely squeezing more trains on to the line that it could handle. Roads are stressful, inefficient and shit. Enforcing a safe stopping distance and pricing journeys accordingly, like trains, is where we want to be.
I-5 is a notoriously congested interstate in California. I don't live in California anymore, but used it simply because there are a disproportionate number of Californians on HN.
I don't disagree about "pricing journeys accordingly," but there are many reasons why this is difficult in practice in the US. Going through those points is a bit of a digression from my main point. Namely, that there are pragmatic tradeoffs that have to be considered. I'm consistently taken aback by the amount of "simple" solutions people advocate on HN and sometimes I wonder if it's due to software developers constantly working with the abstract rather than the concrete.
So is "can you imagine how much infrastructure would cost to ensure everyone drove completely safely"
Like most real-world engineering, there is a cost-benefit balance. Could we design an interstate highway system that allows everyone a 10 car buffer? Sure. Would we like how much it costs, the effects on the environment, etc.? Probably not.
As an aside, your comment seems to go against HN guidelines by taking the least charitable interpretation of the comment.
You might have forgotten the ultimate rule of road safety: Everything is a tradeoff. Safer is only sometimes better. Otherwise the speed limit would be 10mph, because it's quite a safe speed.
So you're saying we should all drive with a 10 car buffer, then?
The only comments saying that are...yours. If your argument is so lacking that you need to argue in bad faith, perhaps it is best to not bother at all.
Or perhaps you are not aware of the proper following distance (and therefore, part of the problem about which you complain). Two car lengths (EDIT: seconds, not car lengths; oops) is the general advice.
I'm just trying to understand exactly what they are advocating, because so many people seem to be making a dichotomous safety choice. It's not a simple model and my point is there are tradeoffs.
>Two car lengths is the general advice.
No. It's speed, roadway, and car dependent. Two car lengths isn't even sufficient at 25mph let alone at 70mph.[1] Which all goes to show how poorly people tend to think about these things and quickly resort to overly simplified mental models.
Moreso that my post has a mistake: two second following distance, not car lengths. Brain fart on my part; apologies for causing you to have to find a URL. But as general rules go, that increases the distance as speed goes up. No, it doesn’t account for everything, but good enough for most circumstances.
So while your statement isn't wrong, it's also not always pragmatic in the real world.