carry on then posted:

You must obey the grid, even when there are surveying errors

PittTheElder posted:

That looks like a correction line, not a surveying error.

RaffyTaffy posted:

You must obey the grid.




Grand Juction CO

Baronjutter posted:

Also the narrow park between Pandora and uhh Pandora was also created out of this error.

fishmech posted:

Doesn't having a correction line inherently mean there was a surveying error you needed to fix?

Baronjutter posted:

I heard the slight jank in the all the roads after they cross Pandora was from a surveying error as well.


Also the narrow park between Pandora and uhh Pandora was also created out of this error.

fishmech posted:

Doesn't having a correction line inherently mean there was a surveying error you needed to fix?

PittTheElder posted:

That looks like a correction line, not a surveying error.

Happy Noodle Boy posted:

Drove by 7-8 separate accidents this morning because of icy roads.

People are loving idiots.

cheese-cube posted:

In states where icy roads are a common problem do driver training programs include learning about how to handle them? Or do driving tests have a "icy road" section or something?

Olympic Mathlete posted:

Chemmy posted:

Yes the local DMV in every state that expects winter weather has an enclosed refrigerated icy road to test new drivers on.

Chemmy posted:

What they really have is a giant slip n slide covered in used motor oil and some old cars to practice skidding around and if you smash up their designated slippery car it's no big deal the government picks up the tab.

Chemmy posted:

My cousin's slippery driving test was done in a warehouse full of banana peels.

Baronjutter posted:

In Scandinavian countries yes, fairly intense instruction and testing including emergency maneuvers on icey conditions.

Steelion posted:

That's a neat video but holy hell that narrator is almost inaudible half the time.

Whiz Palace posted:

I recall Finland actually uses a skidpad to train new drivers. No Koopa shells, but sprinklers and maybe that rack that lifts the car up so it has less contact with the road.

pokie posted:

Is there a good effort post on causes

pokie posted:

and solutions of highway congestion?

pokie posted:

Is there a good effort post on causes and solutions of highway congestion?

Cichlidae posted:

Let me answer your first question really quickly, because the second one is awesome and deserves its own post. The capacity of a freeway depends on the traffic composition I talked about earlier, the grade (slope) of the road, and the geometry of the roadway. On our freeways in Connecticut, we can get 2500 pcplpm (passenger cars per lane per mile) in good conditions, and 1500-1800 when the road is under construction.

One of the many paradoxes of traffic engineering is that traffic flows best when the road is mildly congested. Time to get technical!

We measure how smoothly traffic is flowing by LOS (Level Of Service). A is the best: you're the only one on the road, you can go as fast as you want. At LOS B, there are a couple other cars, but they don't impede you much. LOS C is a bit rougher, and you have to be careful when changing lanes. LOS D is quite stressful. Everyone's moving at a good clip, but you don't have much liberty. LOS E, you're going 10 below the speed limit and everyone's crammed in like sardines. Finally, at LOS F, it's stop-and-go, or just plain 'stop'.



You can see here that speed goes down as volume (and density) go up. However, since there are many more cars on the road at LOS E than at LOS A, even though they're going more slowly, the road is handling more traffic and therefore more efficient. Fascinating, eh? That's why a German road that's often congested can actually be better than an Italian road that nobody uses. Or maybe the Italians just can't drive.

Cichlidae posted:

Alright, it's time to learn about Congestion!

There are two kinds of congestion: recurring, and non-recurring.

RECURRING CONGESTION
This kind of congestion occurs on a regular basis (duh), usually between 6-9 AM and 3-6 PM on weekdays, and around noon on weekends. It's a result of demand exceeding capacity. Remember how roads are most efficient at LOS E, right at the edge of breakdown? That is what scientists would call an unstable equilibrium. Add just a few more cars, and you hit the breakpoint. I'm posting this graph again so you can see; the lower-right graph best shows what I'm talking about.



Once you hit that breakpoint (volume = capacity), drivers get uncomfortable and start slowing down. You see a wave of brake lights. Cars get closer together, capacity drops since everyone's moving slower, and the jam spreads backward. This applies to all roads and all kinds of congestion, even red lights. The big difference is that, in recurring congestion, it's caused by demand increasing, while in non-recurring, it's caused by capacity decreasing.



As you can see, this queue of LOS F, represented by red, spreads upstream. The length of the queue is dependent on two factors: the flow rate upstream, usually about 2200 veh. per lane per hour at LOS E, and the rate at which traffic can depart from a standing queue (green cars to the right), usually around 1500 vplph. When the number arriving is greater than the number leaving, then the queue will keep growing. When it's less, it'll shrink and eventually disappear. For recurring congestion, this only happens once the peak hour is over and the volume drops significantly.

NON-RECURRING CONGESTION
This has a lot of causes: a traffic accident, construction closing a lane or a ramp, bad weather, an elephant walking down the middle of the road... Like I said, the capacity of the road drops. For as long as the capacity is lower than the demand, the queue will build. At some point, it'll be restored, and the queue dissipates. Here's a handy graph showing how we estimate queues, and I'll even leave out the Greek letters, just for you!



The X axis represents time, and the Y axis represents a quantity of cars. Therefore, the slope of lines, cars/time, is a rate. When the arrival rate exceeds the departure rate, a queue builds up, shown in red. Eventually, the departure rate increases, and the queue dissipates. The rest should be self-explanatory, but let me know if you don't get anything.

So the last part of the question is how do we prevent them. For any kind of congestion, there are two means of prevention: increasing capacity and lowering demand. Increasing capacity means adding more lanes, adding a bypass, or increasing the speeds. Reducing demand means getting cars off the road, whether it's by putting people on buses, getting them to carpool, or putting up tolls.

pokie posted:

Is there a good effort post on causes and solutions of highway congestion?