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One line of light rail has a theoretical capacity of up to 8 times more than one lane of freeway (not counting buses) during peak times. Roads have ultimate capacity limits which can be determined by traffic engineering. They usually experience a chaotic breakdown in flow and a dramatic drop in speed (colloquially known as a traffic jam) if they exceed about 2,000 vehicles per hour per lane (each car roughly two seconds behind another). Since most people who drive to work or on business trips do so alone, studies show that the average car occupancy on many roads carrying commuters is only about 1.2 people per car during the high-demand rush hour periods of the day.
This combination of factors limits roads carrying only automobile commuters to a maximum observed capacity of about 2,400 passengers per hour per lane.The problem can be mitigated by using high-occupancy vehicle (HOV) lanes and introducing ride-sharing programs, but in most cases the solution adopted has been to add more lanes to the roads. Simple arithmetic shows that in order to carry 20,000 automobile commuters per hour per direction, a freeway must be at least 18 lanes wide.
By contrast, light rail vehicles can travel in multi-car trains carrying a theoretical ridership up to 20,000 passengers per hour in much narrower rights-of-way, not much more than two car lanes wide for a double track system. They can often be run through existing city streets and parks, or placed in the medians of roads. If run in streets, trains are usually limited by city block lengths to about four 180-passenger vehicles (720 passengers). Operating on 2 minute headways using traffic signal progression, a well-designed two-track system can handle up to 30 trains per hour per track, achieving peak rates of over 20,000 passengers per hour in each direction. More advanced systems with separate rights-of-way using moving block signaling can exceed 25,000 passengers per hour per track.
Since a light rail track can carry up to 20,000 people per hour as compared with 2,400 people per hour for a freeway lane, light rail could theoretically deliver 4 times the congestion-reduction potential per dollar as incremental freeway lanes in congested urban areas.
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Instead of throwing money into more highways, the traffic congestion problem needs a robust rail based mass transit system.
A four track system (2 local, 2 express), would have the equivalent carrying capacity of over 100,000 passengers per hour (replacing 50 lanes of superhighway). That would easily handle the future expansion of the Atlanta metro for the remainder of the 21st century.
Addendum:
A "fast" commuter express, at 100 - 150 MPH, linking up with a more modest 35 - 50 MPH local network, would wean many from the hassles of commuting.
Last edited by jetgraphics; 01-22-2010 at 01:46 PM..
Silly arguments above. The areas in effect are sprawling anyway. Eminent domain is going on as former country lanes become 6 lane boulevards with a center turn lane. People are profiting on once country land becoming a place for more and more shopping centers, business and subdivisions. To think that growth is not heading to these areas because a much needed road was halted is naive.
The only thing the NIMBYs have accomplished is that the sprawl in places like Cherokee, Forsyth and Henry have no limited access to move east/west. The same people are now sitting at stop lights on surface streets instead of moving smoothly on a limited access road. Big difference.
Ummm, I was sort of being facetious, and I'm agreeing with what you're saying to an extent.
While he had some points in that excerpt, I kept wondering who urinated in his cheerios that morning.
Interesting to note that this was written in 1999, so must take into context that he was an early touter of this kind of sour cheerios mindset that is now expounded on ad nauseum by fellow devotees even here on our lovely forum.
From a perspective ten years down the road, would say that changes have been made for the better. Atlanta as a city has prospered, a more dense urban core is coming into fruition. However, a city that has grown like Atlanta will still grow outwards as well and will continue to grow in density in inner and even outer suburbs. If we keep growing (and yes there will be lulls like we are currently in), the people and the services to provide for them will have to go somewhere.
Still think there is a need for more east/west movement in the freeway structure. Here in DFW there are two east west roads north of 635 (Dallas equivalent to 285). The George Bush Tollway would be like having an east/west connect from Town Center to North Pointe to Gwinnett Place. The newly completed Sam Rayburn Tollway would be much like the Northern Arc. Think of how moving around the northern burbs would be easier with two roads like this. Cannot see one single argument that Cobb, North Fulton, Gwinnett, Cherokee and Forsyth would have sprawled any more than they have if these roads were currently in place.
Sorry I missed the facetious side of your previous comment. Funny thing is I had already said the same thing early in this thread some months ago. Didn't take time to read the whole thread before I commented earlier today.
Interesting to note that this was written in 1999, so must take into context that he was an early touter of this kind of sour cheerios mindset that is now expounded on ad nauseum by fellow devotees even here on our lovely forum.
His words on the whole financial meltdown were pretty prophetic though. One thing that will stave off more excessive building is that that rules obtaining loans and buying a house are a lot stricter now. However, he kept on blaming the Sunbelt entirely for this, but the foreclosure crisis affected just about every part of the country.
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Still think there is a need for more east/west movement in the freeway structure. Here in DFW there are two east west roads north of 635 (Dallas equivalent to 285). The George Bush Tollway would be like having an east/west connect from Town Center to North Pointe to Gwinnett Place. The newly completed Sam Rayburn Tollway would be much like the Northern Arc. Think of how moving around the northern burbs would be easier with two roads like this. Cannot see one single argument that Cobb, North Fulton, Gwinnett, Cherokee and Forsyth would have sprawled any more than they have if these roads were currently in place.
True. The suburbs sprawled anyhow regardless of another road being out there. I used to commute from Kennesaw to Clarkston on a daily basis and my route involved using the Top End of I-285 and even on days I wasn't working, I found myself on it having to get from one place to another. I would wake up hating having to drive. A parallel highway probably would've been better in the long run. It would be much easier to get from Alpharetta to Kennesaw to Duluth, etc.
Also, while I'm not the "pave everything down" kind of guy, I do see the need for better freeways and connectivity in Gwinnett County. That county is a mess in terms of getting around. I-85 is horrific during rush hour. I've always thought that extending the Stone Mountain Freeway out towards Loganville, making 316 limited access all the way to Lawrenceville, connecting Ronald Regan Parkway to I-85, etc would go a long way towards moving things around out there.
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Sorry I missed the facetious side of your previous comment. Funny thing is I had already said the same thing early in this thread some months ago. Didn't take time to read the whole thread before I commented earlier today.
And in Houston, their second beltway was a tollroad (even though Harris County promised to remove the tolls after the road was paid off). Same thing with their third beltway.
But regarding the argument saying the outer beltway would make shipping faster... GDOT could achieve the same goal for much less (and with much more benefit) by upgrading the railroads parallel to the busiest trucking corridors and then installing intermodal terminals at key junctions.
Similar to what Virginia and several other states are doing with Norfolk Southern's Heartland Corridor.
Yes, building the first loop wouldn't cost too much, but every additional loop and upgrade costs more.
Of course, as one person mentioned, a lot of politicians liked the project because they thought they could make money off of it. Not the first time something like that happened.
Addendum:
A "fast" commuter express, at 100 - 150 MPH, linking up with a more modest 35 - 50 MPH local network, would wean many from the hassles of commuting.
Umm... light rail has 30-35 mph. An express route is more likely to be constructed from 2 tracks and have 4-lane tracks at local-only stations (2 for stops/2 for through/passing traffic). The time savings on an express is mainly just from decreasing the number of stops the train has.
If you want faster you need to look at commuter rail, regional rail, and HRT, even then their limits are way below 100 mph.
I'm extremely pro-transit, but light rail has been oversold.
It is good for fostering new-growth urban neighborhoods where people need to travel 5-10 miles, but if you look at Dallas an an example suburban use of DART is not that heavy. People can still travel down freeways long distances faster during rush hour.
I think if we build more roadways in Atlanta we need to be smarter about it.... In a sense go big or go home. An outer perimeter tries to stay on the outer edge of suburban growth to cut land costs, but it has has higher mileage/construction costs and pushes growth out further.
I for one would rather see not necessarily full freeways, but access controlled (no curb cuts for neighboring properties) boulevards strategically positioned in already built areas where there is heavy travel demand.
A relatively short boulevard linking Peachtree Industrial/parkway at peachtree corners to Perimeter Center would go heavily used and take congestion away from Spaghetti junction, I-285, and freeway intersections near Perimeter that are heavily congested. Additionally you can have the parkway run into underutilized local roads in both the Peachtree Corners and Perimeter areas.
This is just one minor example of many possibilities. It is relatively high impact, low mileage/lower construction costs (relatively), but high land acquisition cost.
We also need more work on making more local/arterial road access between all counties and across many points on the Chattahoochee, especially between Gwinnett, Dekalb, and Fulton in many places.
This would increase capacity, alleviate congestion, and not necessarily push suburban growth all the way into the Appalachian foothills.
Umm... light rail has 30-35 mph. An express route is more likely to be constructed from 2 tracks and have 4-lane tracks at local-only stations (2 for stops/2 for through/passing traffic). The time savings on an express is mainly just from decreasing the number of stops the train has.
That's the nature of any mass transit that has repeated acceleration / deceleration / acceleration cycles.
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Originally Posted by cwkimbro
If you want faster you need to look at commuter rail, regional rail, and HRT, even then their limits are way below 100 mph.
Speed limits are more a function of regulations than on the physics of rail.
Federal rules also spec a heavier car than European and Asian trains. In addition, current mainline track is optimized for slow, heavy freight, and wouldn't be suitable for superelevation used in other systems.
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Originally Posted by cwkimbro
I'm extremely pro-transit, but light rail has been oversold.
No argument there. Taxpayer subsidized rail is a boon doggle. I prefer private enterprise rail mass transit.
Quote:
Originally Posted by cwkimbro
It is good for fostering new-growth urban neighborhoods where people need to travel 5-10 miles, but if you look at Dallas an an example suburban use of DART is not that heavy. People can still travel down freeways long distances faster during rush hour.
I think if we build more roadways in Atlanta we need to be smarter about it.... In a sense go big or go home.
I think that "more roadways" is a lose - lose proposition.
[] Petroleum costs will be rising
[] Mainline RRs will supplant long haul trucking
[] Rail mass transit can scale up in capacity
[] Population growth and density cannot be accommodated by simply building more highways
[] Electric traction rail will be the inevitable choice (barring a technological breakthrough) for the remainder of the 21st century.
Quote:
Originally Posted by cwkimbro
An outer perimeter tries to stay on the outer edge of suburban growth to cut land costs, but it has has higher mileage/construction costs and pushes growth out further.
I for one would rather see not necessarily full freeways, but access controlled (no curb cuts for neighboring properties) boulevards strategically positioned in already built areas where there is heavy travel demand.
A relatively short boulevard linking Peachtree Industrial/parkway at peachtree corners to Perimeter Center would go heavily used and take congestion away from Spaghetti junction, I-285, and freeway intersections near Perimeter that are heavily congested. Additionally you can have the parkway run into underutilized local roads in both the Peachtree Corners and Perimeter areas.
This is just one minor example of many possibilities. It is relatively high impact, low mileage/lower construction costs (relatively), but high land acquisition cost.
We also need more work on making more local/arterial road access between all counties and across many points on the Chattahoochee, especially between Gwinnett, Dekalb, and Fulton in many places.
This would increase capacity, alleviate congestion, and not necessarily push suburban growth all the way into the Appalachian foothills.
Based on the one track = 9 lanes of superhighway, in equivalent carrying capacity, coupled with the increasing cost for petroleum, added to the limited surface area of the Atlanta Metro area, it's clear that the "highway option" is a bad one.
I predict that as the cost for owning and operating automobiles rise, there will be demand for alternative transportation.
And a robust network of electric powered rail is the optimum solution.
When I was running for Governor of Georgia, I got a standing ovation, interrupting my presentation every time I spoke of that plan. Gov Roy Barnes, incumbent Governor, had stated it was going to cost $1.3 billion just to build a short section of the northern arc of that outer perimeter. I had the numbers on the complete plan I laid out and it was less than a billion to construct AND SERVE HALF THE POPULATION OF THE ENTIRE STATE OF GEORGIA.
How many DECADES is the USA behind on rapid rail? Depends on what you are comparing it to. Moscow built their underground rail system in 1919, and plenty of others are light years ahead of us.
HERE IS THE PLAN: Each major city has an outside circumferential highway with stops at major road intersections. There is a north, south, east, west non stop to the downtown centers. Light rail costs 1/3 of what interstate highways cost! Then, each city has a rail link to a system of national north, south, east west high speed rail systems. Cities link to cities and then those combined links connect to the high speed nationwide rail at a limited number of places.
The major problem is that for example in a lot of states, the DOT does not want rail. It does not need to be constantly maintained. You cant move it around every few years. In ATLANTA, GA the interstate highways were built in 1960, The GADOT has not stopped working on them, moving them around ever since. These people are paranoid about justifying their jobs! With no specific projects the Georgia Legislature increased fuel tax and gave the GADOT A BILLION DOLLARS!
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