[zephjc]

Look to how Tokyo does things. A few takeaways:

- mixed use zoning: reduce requirement for long trips by mixing many compatible types of commercial with residential, and remove single housing type developments. Also, allow many smaller apartment complexes mixed with single family houses, instead of segregating housing types.

- street design: No more hierarchical/dendritic street layouts. That is, no more dead-end streets, which lead to collectors, which lead to arterials - you're bottlenecking a huge population through a very small, fast, and unsafe road system. Instead, make the streets highly connected, and narrower to encourage slower but steadier car traffic, and blocks shorter. Porous streets networks can route around bottlenecks and can have many more concurrent cars than even crazy-huge Texas-style freeways.

- no big street setback requirements: encourage density by removing crazy suburban-style setbacks.

Edit: I wanted to make a plug for form-based zoning, which is zoning where the form (building type) is zoned, not its use. This doesn't necessarily refer to its style (Neoclassical, Modernist, etc) but how it interacts with the surrounding buildings on the street. E.g. buildings above a certain size might not be allowed in an area, and not be allowed to take more than N number of yards of street frontage. Setbacks of a certain size might be prohibited, or allowed. This allows of a reasonable number of mixed uses like restaurants, shops, and other day to day commercial uses to coexist with residential. This does not mean that heavy/noxious industry can be built up there. This was the error the Euclid v. Ambler decision made 100 years ago: they threw the baby out with the bathwater by restricting zoning by type; there is not a small amount of racism that came with Euclidean/exclusive zoning, e.g. removing a formerly viable way for immigrants to start a business with a house above (a la Bob's Burgers) and thereby increasing the barrier for success.

[TulliusCicero]

> - street design: No more hierarchical/dendritic street layouts. That is, no more dead-end streets, which lead to collectors, which lead to arterials - you're bottlenecking a huge population through a very small, fast, and unsafe road system. Instead, make the streets highly connected, and narrower to encourage slower but steadier car traffic, and blocks shorter. Porous streets networks can route around bottlenecks and can have many more concurrent cars than even crazy-huge Texas-style freeways.

Alternatively, you COULD use dead-end streets...that are only dead ends to cars, but have pass-throughs for walking and biking. For an extreme example, see Houten, NL: https://www.google.com/maps/place/Houten,+Netherlands/@52.03...

http://www.citylab.com/cityfixer/2015/06/a-case-study-in-bik...

[zephjc]

Those are pretty recent designs, but I like them for the most part. I agree, as long as you are not hampering human movement, keep car traffic slow and safe for said human movement, networking with bike paths is fine in my book. In an existing dendritic US-style street system, retrofitting with bike paths between streets is a really cheap and easy way to encourage biking (the hardest part is probably dealing with existing property rights)

[nostrademons]

> No more hierarchical/dendritic street layouts.

It's worth playing some Cities:Skylines (which has a fairly accurate traffic simulator, particularly with the Traffic++ mod) to understand how the road hierarchy came into being. Or, for that matter, trying to drive through a grid-based city like Manhattan or SF.

You get very large traffic jams. The problem is intersections, and particularly intersections where traffic backs up to the previous intersection. When this happens, a traffic jam tends to spread across the whole city; incoming traffic can't clear the bottleneck fast enough, so the bottleneck just grows like a cancer until it envelopes a whole neighborhood.

Oftentimes, the solution to a traffic problem is simply to bulldoze a few intersections. By doing this, you give cars a buffer. It increases the median trip length but it also increases vehicle speed and road throughput by more. It turns out that the major contributor to traffic jams is the acceleration of having to start/stop at traffic lights and when turning.

Self-driving cars (or just ubiquitous turn-by-turn navigation) could change this equation by intelligently routing cars around bottlenecks and avoiding the neighborhood entirely, but as long as drivers have imperfect information about traffic conditions and tend to take the shortest route to their destination, this will remain a problem.

(I've had great success with using pedestrian paths to provide cut-throughs between dead-ends and nearby intersections, though. And with providing pedestrian paths under or over those intersections so that people don't have to wait for stoplights to cross the street and don't stop traffic with their jaywalking. The game unfortunately has pretty terrible pathfinding for pedestrians and won't let you build compact staircases, so this limits their usefulness to real problem intersections, but in real life I think many suburban cities could drastically improve their walkability/bikeability just by building raised pedestrian footbridges over their major arterials.)

[thescriptkiddie]

I really enjoy C:S, but even with Traffic++ the traffic simulation is pretty wonky and shouldn't be taken as reflective of reality.

But here's some advice if you're having trouble with traffic jams in your grid systems: use more one-way streets. If you've converted your city over to a 100% one-way grid and still have backups, you probably need to work on your mass transit and freight rail systems. I've made functional cities where every single road was open only to pedestrians, cyclists, and service vehicles. No cars.

[prawn]

Something that also doesn't help with a lot of intersections is dense street parking (blocks line of sight for approaching traffic). It's problematic in cities and getting worse in suburbs. The street I grew up on, was generally empty of parked cars making it a great place to ride or skate in the 1980s. Now, that same street has loads of parked cars - people have second cars, use the street instead of their garage, or their adult children have cars.

Roundabouts would also drastically help many US cities currently relying on all-way stops.

[pc86]

Isn't a large contributing factor to this people being in the intersection ("blocking the box" in NYC) when the light turns red, causing literal gridlock? People, myself included, have a visceral aversion to sitting at a light as it cycles through and not moving, so the instinct is to move forward even if you're going to be sticking into the box a little bit. Then the person behind you does it because they've been waiting just as long as you, and suddenly the perpendicular traffic can't move at all because you're blocking their green light.

I always thought that was why I saw posted fines for blocking the box in NYC but never saw such signs elsewhere (although I've never driven in California).

[coryfklein]

> Self-driving cars ... could change this equation by intelligently routing cars around bottlenecks and avoiding the neighborhood entirely

Self-driving cars can do even better than that - they can eliminate the "stopping" nature of the intersection entirely. If the self-driving cars are able to determine the position and speed of other cars approaching the intersection, you can just have the traffic streams pass right through each other. [1]

[1] Autonomous Intersection Management: Traffic Control for the Future https://www.youtube.com/watch?v=4pbAI40dK0A

[zephjc]

I gotta agree with thescriptkiddie, C:S is an imperfect model of how traffic behaves.

> Self-driving cars (or just ubiquitous turn-by-turn navigation) could change this equation by intelligently routing cars around bottlenecks and avoiding the neighborhood entirely, but as long as drivers have imperfect information about traffic conditions and tend to take the shortest route to their destination, this will remain a problem.

Self-driving cars or drivers with good mapping are still limited where they can go when they have a street hierarchy to deal with, forcing all cars onto the same few arterials.

> Oftentimes, the solution to a traffic problem is simply to bulldoze a few intersections. By doing this, you give cars a buffer. It increases the median trip length but it also increases vehicle speed and road throughput by more.

This is all well and fine in a game, but increasing street speeds kills the street life (figuratively, and sometimes literally). Slower but more constant speeds are better for everyone involved. For walkers, bikers, and even drivers. Ask yourself this: would drivers flip their shit more often when going slow but steady down 15-20 mph hour streets with stop signs (or roundabouts), or when they're stuck at long traffic lights regardless of how many lanes they have?

[greggman]

Tokyo has many intersections with over/underpasses. The 2-4 lanes in the middle go over or under the intersection. The outer lanes connect to the intersection.

That said Tokyo has plenty of traffic.

[verg]

The lack of on-street parking was something I noticed visiting Japan. Streets can be much smaller when they don't have 20-24 feet of parking. In the US, a massive percentage of our most valuable land goes to subsidized vehicle storage. It's insane.

[fudged71]

Narrower streets, wider sidewalks, more trees.

[kbenson]

I remember seeing some video on civil engineering twenty years ago where they talking about how that was a major mistake they had learned from. Arteries just cause traffic jams, while permeable neighborhoods allow traffic to diffuse through it.

[Nadya]

Re: Street Design

Japan is designed with public transport in mind. Most everywhere in Japan is within train/bus/bike/walk distance. You don't need 4 lane high ways when there are maybe a few dozen cards on any particular stretch of the high way at any given time. I drove from Nara, Nara to Naruto, Tokushima via highway and saw maybe ten other cars on the highway. That's a distance of 174.5km; roughly a 2 and 1/2 hour drive. If I drove for 2 and 1/2 hours on any stretch of highway in California, I'd see ten cars every few minutes.

Less cars in the road, in general, means roads can be more narrow.

[zephjc]

For sure. As I understand it a lot of the build-out in Tokyo into what were more rural areas was done by the railroad lines - build a km or two, add a station and more developed land, repeat.

[toast2toast]

I definitely agree!

[whamlastxmas]

Does the perfect city really need to focus on higher population density? It seems like less density is ultimately what most people would want.

[sova]

yes. nature hybridized with human living. future forest primitive

[acgourley]

That's basically the north-of-mainstream thinking in urban planning, right? I certainly agree with you, but I also think it is a wasted opportunity to just build what leading thinkers agree is a good idea.

[zephjc]

More or less. Some aspects of Western urban planning are rather big on things like Complete Streets, where you have segregated bike lanes added between sidewalks and street. These are fine for wider streets as seen in many American cities, but smaller streets which force cars to slower speeds don't necessarily bikes and even pedestrians segregated.

E.g. this slice of suburban Tokyo: https://www.google.com/maps/@35.7368825,139.5634333,3a,75y,2... Note the speed limit is 30kph, or around 18mph.

This seems to be the default building style in much of Japan. You will still find larger streets which are arterial in nature, but they're usually still very bikeable and walkable, and still porous to smaller streets like the one linked above.