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The Irresistible Urge to Build Cities from Scratch

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Re: The Irresistible Urge to Build Cities from Scratch

#21

Post by jermaustin1 »

JoeAltmaier wrote: post #14
rayiner wrote: post #13

Earlier quoted context omitted.

Diagonals can be okay used sparingly, but roundabouts destroy traffic flow the way Americans do them (with lights).

We don't do them that way. In my area, roundabouts are put in where traffic occasionally bursts from one direction, and where traffic levels are low. Because they quit working once traffic increases, because it can be impossible to get on if there's continuous flow from another direction. Maybe the lights reported are because the roundabout has outlived its usefulness? A stopgap before ripping it out.

I think that the size of the round about matters. The larger it is, the more opportunity a driver has to get to an internal lane and not destroy on-ramping from other directions.

Also the timidness of drivers to enter a circle kills the flow and causes a backup that takes time to clear.

I hit 4 different traffic circles on my 40 mile trip home, two of them are 1 lane wide and only about 100 feet wide, the other two are a lot larger and have 2-3 lanes.

The narrow ones [1] back up much quicker during rush hour(s) especially when you have non-commuters using them (you can tell who they are).

The one that is 3 lanes wide [2] usually has a protected lane for only going to the first exit (on then off), then a middle lane that circles the entire roundabout and a middle lane that allows you to exit at any of the exits whenever you want. It works very well. I have never seen a backup on it.

The one that is only two lanes [3] backs up quite a bit during rush hour, when there is a West Point football game or because someone is too scared to enter. The backup clears relatively quickly, but I feel it wouldn't back up at all if there was protected on-ramp.

1: https://www.google.com/maps/@41.324487,-73.8829004,106m/data...

2: https://www.google.com/maps/@41.2981376,-73.935245,212m/data...

3: https://www.google.com/maps/@41.3202891,-73.9909974,212m/dat...

Re: The Irresistible Urge to Build Cities from Scratch

#22

Post by eesmith »

danaris wrote: post #15
rayiner wrote: post #13

Earlier quoted context omitted.

Diagonals can be okay used sparingly, but roundabouts destroy traffic flow the way Americans do them (with lights).

I've...never seen a roundabout with lights. Granted, the state I live in doesn't do them much, but I've visited places (like MA) that do them a lot, and they're all very much like European roundabouts, just with inferior signage.

Here's a rotary in Boston (Sullivan Square) with a traffic light - https://www.google.com/maps/@42.3840002,-71.0744129,3a,75y,9... .

Here's a roundabout in Cape Town (Adderley Street Fountain) with a traffic light - https://www.google.com/maps/@-33.9202591,18.4250697,3a,75y,4... .

Here's one in Cambridge, UK - https://www.google.com/maps/@52.2084812,0.136931,3a,75y,82h,... .

Re: The Irresistible Urge to Build Cities from Scratch

#25

Post by umichguy »

village-idiot wrote: post #17
danaris wrote: post #15

Earlier quoted context omitted.

I've...never seen a roundabout with lights. Granted, the state I live in doesn't do them much, but I've visited places (like MA) that do them a lot, and they're all very much like European roundabouts, just with inferior signage.

We have a few roundabouts in my town in SoCal, small ones, and they all have stop signs.

That's kind of stupid...takes the point away from roundabouts. They're designed to keep the traffic flowing in low /medium conditions when a traffic light or stop sign would bring it to a halt otherwise. Saves on fuel etc.

Re: The Irresistible Urge to Build Cities from Scratch

#26

Post by jackpeterfletch »

jermaustin1 wrote: post #21
JoeAltmaier wrote: post #14

Earlier quoted context omitted.

We don't do them that way. In my area, roundabouts are put in where traffic occasionally bursts from one direction, and where traffic levels are low. Because they quit working once traffic increases, because it can be impossible to get on if there's continuous flow from another direction. Maybe the lights reported are because the roundabout has outlived its usefulness? A stopgap before ripping it out.

I think that the size of the round about matters. The larger it is, the more opportunity a driver has to get to an internal lane and not destroy on-ramping from other directions. Also the timidness of drivers to enter a circle kills the flow and causes a backup that takes time to clear. I hit 4 different traffic circles on my 40 mile trip home, two of them are 1 lane wide and only about 100 feet wide, the other two a…

In countries where they're common place and part of the licensing curriculum, roundabouts are far superior for throughput and traffic flow than any other kind of intersection of comparable size.

To get any further improvement you start having to look at junctions with over head ramps and tunnels.

Re: The Irresistible Urge to Build Cities from Scratch

#27

Post by LoSboccacc »

eesmith wrote: post #22
danaris wrote: post #15

Earlier quoted context omitted.

I've...never seen a roundabout with lights. Granted, the state I live in doesn't do them much, but I've visited places (like MA) that do them a lot, and they're all very much like European roundabouts, just with inferior signage.

Here's a rotary in Boston (Sullivan Square) with a traffic light - https://www.google.com/maps/@42.3840002,-71.0744129,3a,75y,9... . Here's a roundabout in Cape Town (Adderley Street Fountain) with a traffic light - https://www.google.com/maps/@-33.9202591,18.4250697,3a,75y,4... . Here's one in Cambridge, UK - https://www.google.com/maps/@52.2084812,0.136931,3a,75y,82h,... .

One in Milan https://www.google.it/maps/@45.480752,9.2227599,3a,75y,111.4...

there are a load there with lights, tram crossing it straight, pedestrian crossing that aren't on a road crossing etc. makes for some fun time crossing one at peak hour, it's not weird at that time to get stuck in one for 10 minutes or more.

Re: The Irresistible Urge to Build Cities from Scratch

#28

Post by jermaustin1 »

jackpeterfletch wrote: post #26
jermaustin1 wrote: post #21

Earlier quoted context omitted.

I think that the size of the round about matters. The larger it is, the more opportunity a driver has to get to an internal lane and not destroy on-ramping from other directions. Also the timidness of drivers to enter a circle kills the flow and causes a backup that takes time to clear. I hit 4 different traffic circles on my 40 mile trip home, two of them are 1 lane wide and only about 100 feet wide, the other two a…

In countries where they're common place and part of the licensing curriculum, roundabouts are far superior for throughput and traffic flow than any other kind of intersection of comparable size. To get any further improvement you start having to look at junctions with over head ramps and tunnels.

I think because the US only just started adding them, and various other intersection experiments, it will take us some time to become fully comfortable with them.

My wife's family comes from a small town outside of a small town in Louisiana and I remember when they opened the traffic circle there [1], the entire town hated it because they had never in their lives had such bad traffic, because no one knew how to use a yield sign -- stop meant stop, no sign meant yield, but now there is a new triangular stop sign, what the hell man.

Now days though, it flows amazingly, but it took close to a decade. I'm sure it will still improve over time, but now that the entire population has used it, they get it.

1: https://www.google.com/maps/@31.1609199,-93.267374,121m/data...

Re: The Irresistible Urge to Build Cities from Scratch

#29

Post by RightMillennial »

rayiner wrote: post #13
provolone wrote: post #11

Earlier quoted context omitted.

It is nice when they throw in some diagonals and roundabouts for variety. Gives you more options when moving across the city.

Diagonals can be okay used sparingly, but roundabouts destroy traffic flow the way Americans do them (with lights).

As an American, I detest roundabouts. I've never encountered one with a light before.

Re: The Irresistible Urge to Build Cities from Scratch

#30

Post by PhasmaFelis »

barry0079 wrote: post #3

I'm a huge fan of the winding maze like structure of cities built upon the old. It's nice to be able to wander and explore. I suppose blank slate cities (like most in America) are a lot more convenient to navigate though.

Yeah, cities with lots of quirky personality are lovely to visit, but if I'm going to live somewhere I'd prefer it was designed to be livable. There's more compelling character in people, places, and institutions than in street layout.
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