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Comment by sliken | Hacker News Reader

> Why will you _want_ to pass? Is that 10mph going to get you there _that_ much faster?

Actually yes. That truck that's going 60 on the flats is going to be doing much less than that on the hills. Best for everyone involved to pass when it's safe. It increases safety and decreases road utilization.

Keep in mind that 3 hours @ 60 mph is 3 hours with another car on the road. To compensate you'd need another lane for 180 miles, not cheap. Also the rush of passing when a truck slows down is avoided. Additionally it's safer to pass when the speed differences are lower.

Seems better for everyone involved to let cars pass. It's much easier and safer to predict conditions for half the time when passing at +20mph then trying to predict twice as long when passing at +10mph.

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> Best for everyone involved to pass when it's safe. It increases safety and decreases road utilization.

How does it increase safety? Someone else will just catch up to him on that hill.

> It's much easier and safer to predict conditions for half the time when passing at +20mph then trying to predict twice as long when passing at +10mph.

If safety is your concern, then it's even easier and safer to predict conditions without passing until a passing lane opens up, or a turn out is reached for him.

> How does it increase safety? Someone else will just catch up to him on that hill.

Instead of having an ever growing queue of cars that try to pass on the hill, they pass before hand on the flats. So there's not mass chaos when 100 cars who have been trying at 10 mph under the speed limit for an hour all try to pass on the uphill, while the truck is slowing from 60-40.

> If safety is your concern, then it's even easier and safer to predict conditions without passing until a passing lane opens up, or a turn out is reached for him.

Sure, some do that, it's the drivers choice. Personally if passing is allowed, I like to pass slower vehicles. My car accelerates quickly, so I like to pass quickly and spend the minimum amount of time in the oncoming traffic lane.

Just seems natural to let the cars get ahead whenever they can, after all the cars usually have a different speed limit than the trucks. Thus the carefully engineered lane markers, truck specific speed signs, and often passing lanes on the hills.

The minimum amount of time in the oncoming lane is 0

Sure. But now you have to spend more money on adding lanes for the same traffic capacity because the average speed drops.

Road capacity usually increases as speed goes down.

Cars per mile, yes. Cars per second no. If you follow the recommended 3 second spacing then it's a car per 3 seconds per lane.

So for a fixed distance, the slower you go, the longer you are on the road, the more road capacity you consume.

Traffic flow is more stable at lower speeds, so you get less congestion.

A lot of hills have passing lanes _specifically_ for this issue.

By that logic, that the time vehicles are on the road are necessarily limiting capacity of the system, then we should be vastly increasing the speed limit! Why not 100mph? 120mph?

I mean, it's only 3 times the kinetic energy (over 70mph), so any crash would be that much more dangerous/deadly. It's also very wasteful with respect to fuel, so you'd need to stop more often which would decrease your average speed.

Regardless, all of you all drive way too fast as is. It's not safe, it's not efficient.

> A lot of hills have passing lanes _specifically_ for this issue

Sure, but not 100%.

I'm not arguing that speed limits are useless. Just that the speed limits have always been for steady state driving. You can drive all day at them and never get a speeding ticket. However in the interest of safety you should be able to exceed them to pass, this gets the pass over more quickly and is safer and less frustrating for everyone involved.

>> then we should be vastly increasing the speed limit! Why not 100mph? 120mph?

I mean, Poland has 90mph speed limit on motorways and yet it's still safer than US which generally has very low speed limits everywhere. The only reasonable conclusion is that safety isn't directly correlated to the speed limits but to the state of infrastructure, driver training and culture.

> A lot of hills have passing lanes _specifically_ for this issue.

You'll often see heavy truck that's not only slow uphill but also slow downhill, in some cases even more so - because it can't afford to build up speed above what its breaks can handle.

And these passing lanes are _never_ in downhill direction.

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