Hacker News Reader

Comment by taneq | Hacker News Reader

The issue is that when you slow down, you’re (a) creating ‘turbulence’ in the traffic flow with increased speed differential between cars and increased lane changes, which increases accident risk for everybody, and (b) it’s not even solving the problem because you still perpetually have some impatient driver wedging themself in directly in front of you, deleting your buffer zone.

It’s safer to drive a little closer, keep up with other traffic and defend what gap you can in front of you.

Agree with your conclusion here, though. The best response is to simply not drive in this kind of traffic.

View on HN

Hard disagree. It is not safer to ignore your safety buffer. It is certainly not safer to defend your buffer.

If traffic is very busy, the trick is to just accept people will wedge in front of you and keep going slightly smaller each time to increase the buffer again. You might create 'turbulence', which might possibly decrease the safety a bit for all the impatient drivers doing the wedging. But it increases your own safety. And therefore also that of the people following you and your passengers.

I'm also not convinced on the 'turbulence' part. Keeping a buffer smoothes out any sudden speed variations of the people in front of you, which makes the traffic behind you flow better.

And it might maybe feel a lot slower to let a 100 cars go in front of you on your commute, but just driving 99km/h when the person in front of you does 100 is enough to increase your gap and it makes a whopping 1% of difference.

The only thing is: sometimes a road is just too busy and the space for a buffer just isn't there to begin with. At that point the speeds should go down to accommodate the smaller buffers, which is actually what happens here in the netherlands as long as there aren't too many people ignoring the speeds advisory boards above the highway.

> The issue is that when you slow down, you’re (a) creating ‘turbulence’ in the traffic flow with increased speed differential between cars and increased lane changes, which increases accident risk for everybody, and (b) it’s not even solving the problem because you still perpetually have some impatient driver wedging themself in directly in front of you, deleting your buffer zone.

That's very obviously not true. Slowing down always reduces energy in the system and always reduces global turbulence. It's one of the reasons that countries that lower speed limits see journey times reduce.

Is there a statistics name for the last part? I'd like to compare different countries. It's definitely NOT true in Colombia at least, which makes me believe OP more.

We in Colombia had a public service announcement where it showed someone driving really fast (while still respecting semaphores), and another one going with just enough speed. In the end, they both reach the last semaphore almost at the same time and then they part ways. Essentially it shows that driving crazy fast in the city doesn't necessarily gets you faster to your destination.

Now that I'm an adult, I tested it several times, and it matches 90% of my attempts, but that's in the city, with semaphores. No way I'd think letting everybody steal everybody else's buffer would provide for a reduction in journey time, even in highways. You're adding items to a queue, it'll take longer.

Now, it is probably safer, but we can only take so much even if we are not in a rush.

Slowing down on a busy highway does not reduce turbulence at all, it add chaos and unpredictability to the system. Once car suddenly slowing down to create a buffer zone causes the car behind to slow more and more and can often lead to a stop further back. This has been proven time and again on closed loop systems studying highway traffic flow. They are known as "phantom" traffic jams or shockwave traffic jams. Example, https://www.newscientist.com/article/dn13402-shockwave-traff...

> Slowing down on a busy highway does not reduce turbulence at all, it add chaos and unpredictability to the system. Once car suddenly slowing down...

I agree that slowing down "suddenly" causes turbulence. However, slowing down *gradually* allows you to build up a safety buffer which in turn allows you to avoid slowing down suddenly.

Yes, and they are caused by sudden decelerations which are the result of many factors, including driving too fast for the conditions, roadway, and traffic, and tailgating.

> Slowing down on a busy highway does not reduce turbulence at all,

The only thing that reduces global turbulence reliably on any roadway is reducing speed. All the simulations and real-world implementations show this. It's unambiguous and uncontroversial, except that it requires drivers to slow down, which is politically untenable in many jurisdictions.

Reply on news.ycombinator.com