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Old February 10th, 2009, 08:49 PM   #3901
J N Winkler
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Quote:
Originally Posted by FM 2258 View Post
Aside from that wide medians are just great. I'm surprised to see most of the rest of the world using narrow medians even on new highways.
Most of the rest of the world would use wide medians if it could afford them. The first few US freeways were not built with wide medians but those were incorporated in later construction because they offered better protection from nighttime dazzle and crossover accidents without the need to provide central barriers, safety fencing, anti-dazzle plantings or bollards, etc. Wide medians also make it easy to put each carriageway on its own alignment (very useful in hilly or mountainous terrain) and also simplify land acquisition by making it easy to purchase uneconomic remainders.

In Britain, provision of wide medians on the motorway network was studied in the early 1960's. It was determined that the added land cost required to provide medians which would reduce losses from crossover accidents, etc. to the level that could be expected with center barriers would be equal to the cost of constructing an added lane in each direction. Even in the US, wide medians are not used in urban or suburban areas where land is expensive.
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Old February 10th, 2009, 09:04 PM   #3902
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Originally Posted by ChrisZwolle View Post
You can read some more about the freeway lane mileage list on my blog (in English);

http://dutchroadgeek.blogspot.com/20...ion-ratio.html
One other observation. As a generalization, I would expect to see more congestion in a city with a large population than in a city with a small population, even if both cities had the same number of freeway lane miles per capita, equal densities, equally compact development in level terrain free of natural obstacles, and equal intensities of transport usage on a per capita basis.

In the 1970's, the Transport and Road Research Laboratory (in Britain) did a tabletop study to try to assign an upper bound to the amount of road infrastructure that needed to be provided in a city to maintain mobility across the urbanized area, given some basic assumptions about density of housing and employment, mode choice, trip generation, etc. The central finding was that the amount of road capacity required to keep traffic moving at a given level of service increased much faster than population and developed land area.
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Old February 10th, 2009, 09:09 PM   #3903
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I think it also depends on the urban layout... with multiple job centers, traffic flows would mix better, instead of massive tidal flows to one or two centers. You have the same amount of traffic and capacity, yet fewer traffic jams.
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Old February 10th, 2009, 10:39 PM   #3904
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Yup. This is essentially how large cities are able to continue to function. But the stylized fact is that the percentage of uncongested cities you can find in a given size bracket drops with increasing size. There are plenty of uncongested cities in the 100,000-400,000 population range, but far fewer (proportionately) in the 1 million-4 million range.

I suspect the reasons for this are largely economic. Cities do not reach significant size without periods of sustained growth. Growth works by taking the existing infrastructure and sets of transport relations and adding to the burdens on them. This in turn makes it advantageous for existing residents of the city either to accept a lower quality of service or to look for ways for new arrivals to pay proportionately more than they do (cf. California and Proposition 13). By the time a longer-term response to growth arrives in the form of edge cities and dispersed employment, densities have developed to the point where it is not economically feasible to improve the infrastructure to restore the mobility that existed when the city is small. Thus, the city's residents (both old-timers and new arrivals) accustom themselves to trading off congestion for the enhanced job and business opportunities that arise from agglomeration.
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Old February 10th, 2009, 10:46 PM   #3905
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Quote:
Originally Posted by FM 2258 View Post
I think wide medians on freeways are great. I don't want all those headlights right in my face. Plus the U.S. has so much land it doesn't matter how wide the median is.

Edit:

[IMG]http://i43.************/33emwb5.jpg[/IMG]

Look at that beautiful wide-open space.
Funny you should post that particular picture. I-20 is gradually being widened to 6 lanes from Birmingham east to Anniston (and maybe, in the not-too-distant future, the Georgia state line). That median will be gone soon, if it isn't already.
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Old February 11th, 2009, 01:21 AM   #3906
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Quote:
Originally Posted by ttownfeen View Post
Funny you should post that particular picture. I-20 is gradually being widened to 6 lanes from Birmingham east to Anniston (and maybe, in the not-too-distant future, the Georgia state line). That median will be gone soon, if it isn't already.
ALDOT needs to hurry up with that and replace the washboard 1960's concrete that was such a plague on that stretch of road.
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Old February 11th, 2009, 06:04 AM   #3907
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Does anyone know what the "Northern" limit of those raised reflective pavement markings (RPMs) is?

I'm referring to these:



I already know that they have the snowplowable ones for the Northern states and provinces, like so:

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Old February 11th, 2009, 06:39 AM   #3908
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Actually, it has one of the least developed ones in the U.S. for the size of it's population.

And who's gonna buy all those right-of-ways for commuter rail? Every square buildable inch in LA is build.
The government used eminent domain to build the freeways- it can use eminent domain to lay some extra track, which will require FAR less space than a freeway.
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Old February 11th, 2009, 07:50 AM   #3909
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Agree with FM 2258. Sometime when I have the time I'll make a video of the South Western Freeway in Sydney; parts of it have an extremely wide median, it makes for a really great drive.
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Old February 11th, 2009, 11:40 AM   #3910
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The government used eminent domain to build the freeways- it can use eminent domain to lay some extra track, which will require FAR less space than a freeway.
That's true on a one-corridor basis, but the problem is you'll need a whole new network of commuter rail, while there are less freeway corridors/widenings necessary, so on the grand total, commuter rail will need more ROW, and you don't even know how efficient it eventually will be.

In NL, a passenger mile by train takes more space than a passenger mile by freeway, yet our system is far busier than in Los Angeles. So I tend not to be so enthusiast about the claims that rail takes less space for travel demand.

Los Angeles should rather build some subway networks, and maybe some rail corridors above those canals, so you don't need a new ROW through neighborhoods.

The problem is
1) There's no money
2) Transit travellers do not want to pay the actual cost of their modal choice.
3) Hence fare revenue is too low to cover the infrastructure and operational costs.
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Old February 11th, 2009, 12:23 PM   #3911
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Quote:
Originally Posted by rick1016 View Post
Does anyone know what the "Northern" limit of those raised reflective pavement markings (RPMs) is?
I don't know the answer to your question, but I do know that many places also use reflecters that are "dug into" the pavement as well, which obviously won't get ripped out by a plow. Of course that option also prevents the dual use of making a noise when you run over them.
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Old February 12th, 2009, 06:30 AM   #3912
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Yeah that's true. They have a few of those in some areas of Ontario as well. One area that comes to mind is on Highway 403 heading up the Hamilton "mountain".

You can't really see them, but they're around here I believe:



Disclaimer: Photo is not mine, comes from onthighways.com
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Old February 12th, 2009, 08:00 PM   #3913
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Quote:
Originally Posted by ttownfeen View Post
Funny you should post that particular picture. I-20 is gradually being widened to 6 lanes from Birmingham east to Anniston (and maybe, in the not-too-distant future, the Georgia state line). That median will be gone soon, if it isn't already.
That sure does look like a crowded rural freeway kinda like rural Interstate 35 here in Texas between San Antonio and Hillsboro (before the 35E/35W split).

I see no downside to wide medians. Here in central Texas when the y built the new tollway system they incorporated wide medians for future expansion.
[IMG]http://i39.************/huobnp.jpg[/IMG]
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Old February 12th, 2009, 10:44 PM   #3914
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The downside is that it takes up and wastes and enormous amount of space, especially since a lot of these expressways run through urbanized areas.
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Old February 12th, 2009, 10:46 PM   #3915
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In Texas there is unlimited space

See what happened to the suburbs in Texas, they reach very far, but there is a lot of undeveloped land in between. Still Texas is not the biggest state of the US
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Old February 12th, 2009, 10:57 PM   #3916
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That's only true for Houston. Every space in DFW is pretty much used.
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Old February 13th, 2009, 12:43 AM   #3917
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Old February 13th, 2009, 05:00 AM   #3918
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Quote:
Originally Posted by ChrisZwolle View Post
The problem is
1) There's no money
2) Transit travellers do not want to pay the actual cost of their modal choice.
3) Hence fare revenue is too low to cover the infrastructure and operational costs.
LA has the ROW already in place to expand its commuter rail network. There are plenty of rail lines that run through SoCal. The Metrolink system runs on freight track.

I am talking about adding additional track along existing Metrolink routes.

And highways do not pay for themselves either. They require large amounts of subsidies to maintain. So why is this fact seen as OK for roads but not for railroads?
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Old February 13th, 2009, 05:12 AM   #3919
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That's only true for Houston. Every space in DFW is pretty much used.
You are wrong, there is plenty of space in the DFW area.
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Old February 13th, 2009, 10:17 AM   #3920
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And highways do not pay for themselves either. They require large amounts of subsidies to maintain. So why is this fact seen as OK for roads but not for railroads?
Subsidies brought in by tax derived from automobility! This is a big difference with rail, where used tax are from general sources.
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