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This is fascinating. The book Traffic [1] talks a great deal about how adding road capacity (e.g. more lanes) can result in zero change in congestion because more people choose to take more trips.

But this paradox appears to hold traffic constant, and uses game theory to show how more connections (not lanes) can result in worse congestion too.

It really is amazing how something as simple-seeming as roads and traffic, where it feels like simple common sense ought to apply, winds up being so deeply and fundamentally counter-intuitive.

[1] https://www.amazon.com/Traffic-Drive-What-Says-About/dp/0307...

⬐ ProblemFactory

> adding road capacity (e.g. more lanes) can result in zero change in congestion because more people choose to take more trips

This is not the paradox nor even an argument against adding road capacity though.

Even if congestion or travel times stay the same, now more people are able to travel to places they want to go. Traffic might not have improved, but some measure of quality of life did.

⬐ X6S1x6Okd1st

Depends on the impact of sitting in traffic on quality of life.

⬐ dsfyu404ed

You can still forgo the trip though. It's up to each individual participant to decide whether or not they want to make the trip. The ability for more people to take the trip at the same opportunity cost. Adding a lane or a road is little different than increasing the frequency of trains on a subway.

Peak demand will always saturate whatever capacity you have but the amount of stuff you move at peak capacity is greater so you spend less time fully saturated

⬐ X6S1x6Okd1st

> Peak demand will always saturate whatever capacity you have but the amount of stuff you move at peak capacity is greater so you spend less time fully saturated

That doesn't follow.

So, which was the traffic simulator you worked on? I've always been fascinated by traffic and traffic modelling, read books [1], seen articles where they use cellular automata, psychology, discrete events, etc etc.

[1] https://www.amazon.com/Traffic-Drive-What-Says-About/dp/0307...

⬐ KGIII

I'd prefer to not disclose the specific names for reasons of a modicum of privacy. It's long since sold, anyhow.

But, yes! It's absolutely amazing what goes into modeling traffic as accurately as possible. When we expanded to model pedestrian traffic as well, we even went so far as to build a mock store.

It's fascinating to see how small changes can influence traffic and alter the throughput. Simple things, like frequency of signage has a large impact. There are also regional differences where whole regions will, as an average, drive very differently.

You can run all the models, collect all the data, and someone will still get drunk and reverse the wrong way on a one way street. You'll never get perfect predictions and so there are constant changes being made. That kept it interesting.

What I worked on was all proprietary. It'd be interesting to see an open source project in this arena.

I'm not sure I'm understanding your position very well. Are you saying that people exiting the slow lanes to enter the "moving lane" constitutes a hazard, and by punishing those actors by not letting them in, you are minimizing that hazard? If so, i'm inclined to agree philosophically.

However, I don't believe anyone should impose their philosophy with 2 tons of steel.

RE: traffic science, here are some references http://www.amazon.com/Traffic-Drive-What-Says-About/dp/03072... http://www.edmunds.com/driving-tips/car-merging-psychology-d...

If you're really interested in the subject and want to read more without dealing with the wanky blogger writing style check out "Traffic: Why We Drive the Way We Do" (http://www.amazon.com/Traffic-Drive-What-Says-About/dp/03072...).

Very cool! I remember reading about this before. It seems like a weird concept and makes some people mad, but it's real.

If you like reading and have ever spent more than an hour or two thinking about traffic and American car culture, consider reading this http://www.amazon.com/Traffic-Drive-What-Says-About/dp/03072...

If you enjoy this sort of stuff, the book Traffic: Why We Drive the Way We Do (and What It Says About Us) by Tom Vanderbilt[1] is an enjoyable read. He covers traffic waves and a lot more.

[1] http://www.amazon.com/Traffic-Drive-What-Says-About/dp/03072...

I read about a study in the book Traffic[1] that seems to negate this view, for buses at least. The findings were as follows:

1. More people use buses along a certain stretch of road.

2. Said stretch of road sees less congestion. Bus riders save time!

3. Noticing that this road has less congestion, more drivers take this route.

4. Route becomes congested due to increased interest.

5. Buses take just as long as cars to get to destination.

6. Bus riders migrate back to cars due to lost advantage of bus.

7. Road is more congested than before.

Overall, Traffic is a fantastic read and really opened my eyes.

[1] http://www.amazon.com/Traffic-Drive-What-Says-About/dp/03072...

⬐ kbenson

Is this a case study, or a way something "could" go bad? Specifically 6. Bus riders migrate back to cars due to lost advantage of bus seems to encompass some assumptions that aren't necessarily true:

1) Bus riders have cars

In SF, many people don't own cars because the city isn't particularly car friendly. If buses get too slow, I can see some riders using alternate transportation, but I doubt very many would choose to use a car (and most probably don't have one to use).

Note: I don't live in SF, but was born, raises and continue to live an hour North. My primary mode of travel there is in a car, and it's not ever pleasant.

2) Bus riders ride buss primarily because it's quicker

What about being cheaper? What about convenience (it's a different type of convenience, but it's liberating to not have to worry your vehicle is safe and whether you've forgotten keys somewhere).

⬐ None

None

⬐ clarkmoody

Think of a suburbs -> downtown commute situation. Houston comes to mind here.

I believe that was the study. I'll have to go look at the source to be sure, though.

Speaking of convenience factor, I can't wait for self-driving cars in this regard. I know it's a topic change, but widespread autonomous transport will clear up much of our traffic problems. Indeed, humans are the weak link when it comes to traffic. Not roads, signs, capacity, mass-transit, etc. but humans. We're just not capable of coordinating our behavior in traffic.

⬐ clarkmoody

I found the relevant section in my copy of Traffic:

  ...congestion pricing can help reverse a long-standing
  vicious cycle of traffic, one that removes the incentives
  to take public transportation. The more people who choose 
  to drive to work, the worse the traffic. This raises the
  time the buses must spend in traffic, which raises the
  cost for bus companies, who raise the fares for bus
  commuters -- who are being penalized despite their own
  efforts to reduce total traffic. As the bus becomes less
  of a good deal, more people defect to cars, making things
  worse for the bus riders, who have even less incentive to
  ride the bus. (p. 167)

The author cites congestion pricing as the solution, with money raised going to pay for buses.

And this brings us full-circle to the argument that those buses should be free for riders. If a city charged cars to drive during congested times and subsidized bus fares with that money, this might be a solution to ease up congestion.

⬐ kbenson

> Think of a suburbs -> downtown commute situation. Houston comes to mind here.

> I believe that was the study. I'll have to go look at the source to be sure, though.

That makes more sense, although I have to imagine some prioritization of public transit would alleviate this somewhat.

> Speaking of convenience factor, I can't wait for self-driving cars in this regard

Imagine self driving mixed with public transportation. Instead of large buses (or in addition to) we could have more, smaller vans, seating 6-10, depending. We could have multiple per prior bus serviced route if replacing a bus, and they could be more accurately dispatched base on load (having a bus service a route when there's few to no riders is a waste). Additionally, these could be used to add less commonly used, but still beneficial routes between farther points.

To really make it next gen, you could allow people to reserve seats online for a small fee, which would give useful information on route usage and upcoming demand, to allow reserve units to be dispatched accordingly.

If the cost of the drivers is removed, and the vehicle cost and repair can be brought down, a lot of really interesting things could be done with public transit.

⬐ danmaz74

When I was attending university, there was a big problem with parking. So they built lots of parking space, more or less they tripled the parking lots. Net effect: there was still the same problem with parking, but now there was also a bigger traffic problem. On the other hand, buses were less crowded :)

⬐ dllthomas

5 => 6 seems odd. The advantage of the bus is basically never that it gets you to your destination faster. Buses stop every couple blocks; they're not going to beat cars taking the same route and not stopping.

The advantage of the bus is 1) it's (hopefully) cheaper; 2) I can put the time to better purpose than staring at the road and listening to NPR; 3) I don't have to be frustrated by parking; 4) if I meander from where I started I don't have to make my way back there; 5) (addendum to 1) for my commute I can spend pre-tax money on it, making it cheaper still.

For me, I find 2 the most important, though sometimes 3 is substantial.

⬐ showerst

You're forgetting one of they key points of buses in dense places: Parking!

Here in DC I can out-drive the bus on any route in the city, but when you factor in 20+ dollars/day for parking downtown, or spending 30 minutes finding a street spot, the bus wins hands down.

⬐ dllthomas

Parking was number 3, though I'll admit I may have underplayed it.

I don't have a study to link to

but I'm seen how one slow driving cop can cause a bottle neck behind him as noone wants to pass him

some links about about how seemingly minor factors can cause traffic jams

http://auto.howstuffworks.com/car-driving-safety/accidents-h...

http://www.amazon.com/Traffic-Drive-What-Says-About/dp/03072...

⬐ talmand

The cop car obeying the speed limit and every one behind it doing the same is not an example of congestion. As long as the cars are flowing at the posted speed limit then I don't see that as congestion, the traffic is just not speeding along as quickly as one wishes it would.

By that logic, any street that has two or more cars following the speed limit in close proximity to each other could be classified as congestion.

Once you have a buildup of cars that are traveling slower than the intended speed of the road that causes further slowing up the line that eventually creates bumper-to-bumper traffic with little movement, then you have congestion.

There's an interesting book on the topic, focusing on the way human behavior affects traffic patterns. It's similar to other behavioral anthropology books like Dan Ariely's 'Predictably Irrational'.

Tom Vanderbilt - Traffic: Why We Drive the Way We Do (and What It Says About Us) (http://www.amazon.com/Traffic-Drive-What-Says-About/dp/03072...)

For anyone else fascinated by traffic patterns and driver behavior, I recommend reading Traffic: Why We Drive The Way we Do and What It Says about Us

The author goes into fascinating detail about driver psychology and discusses similar ideas like those mentioned in the essay.

Link to book: http://www.amazon.com/Traffic-Drive-What-Says-About/dp/03072...