Highway Meduims for New Rail Contructions

Seen it done in Toronto,Chicago and the lastest in Utah...Some of the grades in places may be two steep like on some portions of NY states southern teir expressway but its existing land rather then fighting with the freight railroads

Medians are often unavailable and highway curves tend to be too sharp for high speed rail.

you having question or making a statement ??
since no real new High speed rail is being proposed whats your point ??

Jeez... tough crowd here tonight....Every time I am in a car on a long drive with friends and railroads come up as a topic they say-
"why dont they build high speed rail in the medium strip" So New York State Thruway instead of funding a ditch that no one uses (erie canal) could use its turnpike tolls to build high speed rail in the medium strips

The route should be chosen based on which is the best ROW irrespective of what type of ROW it follows. That said, freeways are actually very good option for HSR ROW's because it's already in government hands and there tends to be plenty of available space in the median. There are two problems associated with it however. 1) Freeway ROWs don't have as central locations as railroads do when you get into urban areas and they also lack the area to build stations. 2) An ROW that suits automobiles doesn't necessarily suit HSR. The biggest problem tends to be that the route is too twisting for a high speed train to get up to speed. Grades can also be a problem but they aren't nearly a problem for HSR as they are for conventional trains; the high speed and lightweight allows the trains to climb higher grades.

In Florida, there was a concern over the fact that using I-4 would mean that HSR would miss downtown Lakeland and instead serve it from a suburban greenfield location. In California, some groups are calling for using I-5 between Bakersfield and Los Banos but this comes at the cost of losing all of the Central Valley cities along the route.

There are plenty of stations were I have walked down a set of steps or taken a elevator down from a bridge that crosses to a medium strip were Metro or Commuter Rail has been built like the new DC metro thats going to Tyson Corners or Torontos Subway. With a good chunk of populations living in suberbia these freeway high speed routes would be park and ride alt to drving

JBHUNTFAN wrote:There are plenty of stations were I have walked down a set of steps or taken a elevator down from a bridge that crosses to a medium strip were Metro or Commuter Rail has been built like the new DC metro thats going to Tyson Corners or Torontos Subway. With a good chunk of populations living in suberbia these freeway high speed routes would be park and ride alt to drving

There is a huge difference in the infrastructure requirements of a high speed railway and a metro/commuter rail stop. The latter usually consists of a platform, a roof, and a few ticket machines. Maybe some gates or stairs. High speed rail stations are more on the order of anywhere between an intermediate sized Amtrak station (maybe the size of Albany?) to something like a Hauptbahnhof or Grand Central. Either way, you can't just fit an HSR station in a median strip the same way you can with a commuter line. It's possible but it requires entirely re-engineering, demolition, and construction. Not that that median strips are even something that should be desired to begin with.

HSR stations should almost always be built in a brownfield location in urban centers. It's the most economically efficient and potent location and it attracts the greatest number of riders. Remember, destinations are in cities, not in suburbs and certainly not in freeway medians. Park-and-rides just encourage the freeway and sprawl culture that makes it hard to implement transit to begin with. Incidentally, a blogger that goes by the name Cap'n Transit wrote a couple of blog posts about this in the past few weeks. Feel free to chime in.

http://capntransit.blogspot.com/2012/02 ... k-and.html
http://capntransit.blogspot.com/2012/02 ... l-and.html

Following freeways in rural areas is okay with me. But I think HSR should have stations in or near central business districts of urban cities. Rail lines can enter or leave (depending upon direction of travel) freeway medians as needed, they aren't required to stay there.

I was trying to figure out what psychics had to do with rail construction...

The big problem is right-of-way curvature. The acceleration going through a curve is
a = v^2/r = k*v^2
for speed v, radius of curvature r, and curvature k (= 1/r).

LGV Sud-Est - Wikipedia -- most of it has a minimum radius of curvature of 4 km, though there are some curves that get down as low as 3.2 km. That's the radius of curvature, not the length of the curved sections.

That LGV's center-to-center track spacing is 4.2 m / 14 ft, and its right-of-way is thus at least 28 ft wide. From Lane - Wikipedia, the US Interstates have a standard lane width of 12 ft, meaning that a HSR ROW will have the width of at least 2 lanes and likely more. Given the typical width of many freeway medians, the freeways will have to be widened to accommodate a HSR ROW.

TGV trainsets have widths that go up to 2.9 m / 9.5 ft, something which seems typical of high-speed trains.

JBHUNTFAN wrote:Jeez... tough crowd here tonight....Every time I am in a car on a long drive with friends and railroads come up as a topic they say-
"why dont they build high speed rail in the medium strip" So New York State Thruway instead of funding a ditch that no one uses (erie canal) could use its turnpike tolls to build high speed rail in the medium strips

The proposed line between Tampa and Orlando was going to be in the median, where I have noticed plenty of space - but it was cancelled by the governor.

lpetrich wrote:The US Interstates have a standard lane width of 12 ft, meaning that a HSR ROW will have the width of at least 2 lanes and likely more. Given the typical width of many freeway medians, the freeways will have to be widened to accommodate a HSR ROW.

Many US Interstates pavements are reaching end of life. We're repaving (not resurfacing) miles of interstates lanes as is, both rural and urban. That's a poor excuse.
The radius excuse is valid. Here's a great source for highway design and minimum curve radii.
http://onlinemanuals.txdot.gov/txdotman ... m#BGBJCCFI
Design Speed (mph) = Minimum Radius (ft)
15 = 690
20 = 1220
25 = 1760
30 = 2410
35 = 3160
40 = 4010
45 = 4970
50 = 6030
55 = 7210
60 = 8500
65 = 9590
70 = 10750
75 = 12000
80 = 13340
Assuming 70 mph was the designed speed of a rural freeway as it is in Texas, that's the equivalent of 2 miles, or 3.2 kilometers for minimum radii. That's not near the 4.0 kilometers TGV prefers for HSR operations, but meets TGV minimums.
Of course high speeds freeways are usually built with superelevation. Another chart with the US customary 6% superelevation..
Design Speed (mph) = Usual Min. Radius of Curve (ft) = Absolute Min. Radius of Curve (ft)
45 = 830 = 660
50 = 1055 = 835
55 = 1645 = 1065
60 = 2210 = 1340
65 = 2735 = 1660
70 = 3405 = 2050
75 = 3775 = 2510
80 = 4605 = 3060
With superelevation being used on high speed highways, it doesn't look good for HSR in freeway medians. But these are minimum curve radii numbers, not what is normally designed and built.

p.s. Just wanted to add the some states, like Texas, put curves in Interstate highways when they're not needed to reduce the odds of drivers falling asleep at the wheel. A perfectly straight highway several miles long usually can't be found in America.







lpetrich wrote:The big problem is right-of-way curvature. The acceleration going through a curve is
a = v^2/r = k*v^2
for speed v, radius of curvature r, and curvature k (= 1/r).

LGV Sud-Est - Wikipedia -- most of it has a minimum radius of curvature of 4 km, though there are some curves that get down as low as 3.2 km. That's the radius of curvature, not the length of the curved sections.

That LGV's center-to-center track spacing is 4.2 m / 14 ft, and its right-of-way is thus at least 28 ft wide. From Lane - Wikipedia, the US Interstates have a standard lane width of 12 ft, meaning that a HSR ROW will have the width of at least 2 lanes and likely more. Given the typical width of many freeway medians, the freeways will have to be widened to accommodate a HSR ROW.

TGV trainsets have widths that go up to 2.9 m / 9.5 ft, something which seems typical of high-speed trains.

Thanks for the information lpetrich! I knew HSR lines needed a very large turning radius but I'm happy to have a number now. There might not always be room in the median but there should be enough or almost enough room the freeway ROW for an HSR line. Keep in mind that freeways on the ROW for about 4 or 5 meters on either side plus the median space. You could conceivably move all the lanes on one side of the freeway over to remove the median and use the resulting space to build the HSR line. That might be pushing it proximity-wise though to both road traffic and property adjacent to the freeway. And while that curvature might work in theoretically, I suspect that real-world application is going to be a more nuanced version of that equation.

electricron, thanx for finding those numbers.

trainmaster611, thanx for your sympathy. I don't see how physics geekiness is much worse than railroad geekiness, especially when the physics is relevant to some railroad issue, like track-curvature limits.

From the TGV design limits (r = 4 km, v = 300 km/h), I find a sideways acceleration of 1.7 m/s^2 or 1/6 g.
For a non-superelevated highway curve, I find 0.3 m/s^2
For a superelevated one, I find 0.9 m/s^2 (usual max) and 1.4 m/s^2 (extreme max)

JBHUNTFAN has taken a one way 40mph train away from here.

I removed the inflammatory references to nerds and bbws.

We can continue to discuss the topic however.