For a presentation IÂ’ll be making here in the midwest flatlands, I want to compare the steepest grade on the San Francisco cable car system (21%) with a more familiar situation for the audience. What might be the maximum grade allowable on a mainline railroad and/or a typical highway even in mountainous terrain such as in nearby Colorado? (I assume grade standards are pretty much the same across the US.) Thanks for any help you can offer!

> For a presentation IÂ’ll be making here in
> the midwest flatlands, I want to compare the
> steepest grade on the San Francisco cable
> car system (21%) with a more familiar
> situation for the audience. What might be
> the maximum grade allowable on a mainline
> railroad and/or a typical highway even in
> mountainous terrain such as in nearby
> Colorado? (I assume grade standards are
> pretty much the same across the US.) Thanks
> for any help you can offer!

Well, Saluda Mountain in North Carolina is pretty steep, and it's been variously reported at anything from 5% to 7%.

The steepest hill we've got at SCRM averages to 1.6% over about a mile, with a short stretch (maybe 250 feet or so) of 2.3%. I can tell you from experience that trying to lug anything up that 2.3% section can get interesting, especially in high summer when the weeds are thick and juicy.

Generally, 3% is accepted as the maximum practical grade -- of course you always want to minimize gradients whenever possible.

The South Carolina Railroad Museum
mconrad@msmgmt.com

> For a presentation IÂ’ll be making here in
> the midwest flatlands, I want to compare the
> steepest grade on the San Francisco cable
> car system (21%) with a more familiar
> situation for the audience. What might be
> the maximum grade allowable on a mainline
> railroad and/or a typical highway even in
> mountainous terrain such as in nearby
> Colorado? (I assume grade standards are
> pretty much the same across the US.) Thanks
> for any help you can offer!

Mainline railroads will generally avoid building anything above 2% if possible. Even 1.5% causes problems, requires helpers, etc. Examples of some noted (maximum) grades (all of the top of my head memory):
Horse Shoe Curve, Pa. (PRR): 1.75-1.8%
Sand Patch, Pa. (B&O): 1.93%
Terra Alta/17-Mile, Md./WV (B&O): 2.28%
Cajon Pass, California (ATSF/SP): 2.2% (originally 3%)
Tennessee Pass, Col. (D&RGW, now defunct): 3%
Raton Pass, New Mexico (ATSF) is the steepest stretch of mainline trackage in the USA at this point, with a grade around 3.05% or so
Saluda Grade, NC (SR) was, until it was taken out of service recently, the steepest mainline grade in America at 4.7%
Steepest branch that I know of: Madison Hill in Indiana, now defunct (sees movements to a power plant about once every 10-15 years), 5.89%

Steepest I've ever seen: Parts of the Cass Scenic RR in West Va. has stretches of up to 11%



LNER4472-NOSPAM-@bcpl.net

> What might be
> the maximum grade allowable on a mainline
> railroad and/or a typical highway even in
> mountainous terrain such as in nearby
> Colorado? (I assume grade standards are
> pretty much the same across the US.)

Highway grade standards vary from 4% to 7% maximum, depending on what terrain the highway is built in and the length of the grade.

Railroads tend to look at anything more than 1% as "steep" on a mainline. Typical eastern mountain grades like Blue Ridge and Christiansburg on the N&W, or the B&O's various Alleghany/Allegheny/Alleghenies crossings, are 1.2%-1.8% if memory serves. Western grades tend to be a bit steeper - Cajon Pass is 2.2%, I believe.

JAC

> For a presentation IÂ’ll be making here in
> the midwest flatlands, I want to compare the
> steepest grade on the San Francisco cable
> car system (21%) with a more familiar
> situation for the audience. What might be
> the maximum grade allowable on a mainline
> railroad and/or a typical highway even in
> mountainous terrain such as in nearby
> Colorado? (I assume grade standards are
> pretty much the same across the US.) Thanks
> for any help you can offer!

Doctrine is generally, max grade for standard gauge is 2% and three foot narrow gauge operated routinely at 4%. But to maximize the efficiency of your system, grades should be kept to the minimum that are practicable considering land costs, rail costs, verses fuel costs, maintenance costs etc. In “American Narrow Gauge Railroads” by George W. Hilton, there is a complete discussion of the cost heavy grades placed on operations. Here’s a little table to give you an idea of what grades really mean:

Distance to climb Ft/Mile British
1000 feet at: (Feet)
.25% 75.75 miles 13.2 1 in 400
.5% 37.87 miles 26.4 1 in 200
1% 19 miles 52.8 1 in 100
2% 9.5 miles 105.6 1 in 50
3% 6.31 miles 158.4 3 in 100
4% 4.73 miles 211.2 1 in 25
5% 3.78 miles 264.0 1 in 20
6% 3.16 miles 316.8 3 in 50
7% 2.71 miles 369.6 7 in 100
8% 2.37 miles 422.4 4 in 25
9% 2.10 miles 475.2 9 in 100
10% 1.89 miles 528.0 1 in 10

I-70 west of Denver has a ruling grade of 7% on Floyd Hill which is about the maximum for Interstate highways. Some state highways have grades of 12%. Some D&RG branch lines had grades of 5%, many logging RR had ruling grades of 6 to 9 percent. But the reduction of load carrying capacity makes those grades economically quite costly. Following link from the Pikes Peak Cog Railway site will give you some of the performance issues with cog railroads.

Ed


Pikes Peak Cog Railway history

Distance to climb ..... Ft/Mile ... British
1000 feet at: .............................. (Feet)
.25%.....75.75 miles .... 13.2 .... 1 in 400
.5% .... 37.87 miles .... 26.4 .... 1 in 200
..1% ....... 19 miles ..... 52.8 .... 1 in 100
..2% .... 9.5 miles ...... 105.6 .... 1 in 50
..3% .... 6.31 miles ..... 158.4 .... 3 in 100
..4% .... 4.73 miles ..... 211.2 .... 1 in 25
..5% .... 3.78 miles ..... 264.0 .... 1 in 20
..6% .... 3.16 miles ..... 316.8 .... 3 in 50
..7% .... 2.71 miles ..... 369.6 .... 7 in 100
..8% .... 2.37 miles ..... 422.4 .... 4 in 25
..9% .... 2.10 miles ..... 475.2 .... 9 in 100
10% ... 1.89 miles ..... 528.0 .... 1 in 10

Ed

There is a theoretical maximum grade for adhesion between a steel wheel and steel rail, without rack or cable assist. I have heard this cited as 10-percent. Engineering majors out there??

tr2manz@frontiernet.net

> There is a theoretical maximum grade for
> adhesion between a steel wheel and steel
> rail, without rack or cable assist. I have
> heard this cited as 10-percent. Engineering
> majors out there??

I'm not an engineering major, but Cass Scenic R.R. has a short 14% grade, just before reaching Bald Knob.

dougnleffler@yahoo.com

> I'm not an engineering major, but Cass
> Scenic R.R. has a short 14% grade, just
> before reaching Bald Knob.

According to the Mountain State Railroad & Logging Historical Assoc., the steepest part of Cass is the new line into Bald Knob at 9%, with the "S" curves just below Whittaker at 8.7%.

Max grade for a rod engine is probably somewhere around 8%. Not sure about geared engines, but my guess would be somewhere in the neighborhood of 14-15%. You hear about a LOT of logging railroads with grades in the 10-12% range, but but don't remember hearing of any offhand that are steeper than that.

Kevin

k_gilliam@bellsouth.net

> According to the Mountain State Railroad
> & Logging Historical Assoc., the
> steepest part of Cass is the new line into
> Bald Knob at 9%, with the "S"
> curves just below Whittaker at 8.7%.

I guess the Histerical Society knows more than the people that run the train at Cass, as they advised us on the train, on a trip that I took many years ago, that the grade was 14% just below Bald Knob. In any event...it's steep!

dougnleffler@yahoo.com

> According to the Mountain State Railroad
> & Logging Historical Assoc., the
> steepest part of Cass is the new line into
> Bald Knob at 9%, with the "S"
> curves just below Whittaker at 8.7%.

> Max grade for a rod engine is probably
> somewhere around 8%. Not sure about geared
> engines, but my guess would be somewhere in
> the neighborhood of 14-15%. You hear about a
> LOT of logging railroads with grades in the
> 10-12% range, but but don't remember hearing
> of any offhand that are steeper than that.

I guess the question boils down to, how much weight do you need to move up that grade. On the "Geared Steam Locomotive Works" site, they have a load verses grade table from Davenport. The Davenport "Dryope" six coupled geared engine can haul 786 tons up a 1/2% grade and is de-rated to only 65 tons on a 8% grade. In the logging industry, they often set up inclined planes with a donkey winch at the top to haul loads up the really steep places.

There are also a lot of variables in figuring traction. The amount of contact, the weight on the drivers, the amount of turn, the shape of the rail head, etc. So it really boils down to "best practice."

Ed

I did a report on the Shay locomotive a while ago, and if my memory serves me correctly, a Shay was designed to take up to 14% grade, but I think climbed a 16% grade.

jsfrost@mtu.edu

Curves, even super elevated ones, can hurt tonnage ratings badly. I once worked on a Texas shortline, and we had a .8 mile piece of 3.5%. We could do OK with our usual power set and 65 loads -- until we hit the curve, about 3/4ths of the way to the top.

To get over the grade, which was the purpose of the run, required hauling only 58 loads around the curve. We often would set out with 75+ loads (drilling sand) and then "double the hill," roughly splitting the train in half and making two trips.

Engineers -- civil and mechanical -- can supply formulae. Brush up on calculus. Railroad engineers deal in more abstractive, applied terms. Hope this helps in your presentation.


amiller@rtms-movietrains.com

Was it not 4.? miles at 4.8% ?

Information anyone?

amiller@rtms-movietrains.com

The Uintah Railway from Dragon, Utah to Mack, Colorado had 7.5% grades and ran the only 2 narrow gauge tank mallets built for use in the US. The Roaring Camp and Big Trees has a section of grade that exceeds 15 % on Bear Mountain in Felton California. I have herd that the maximum theoretical grade that an adhesion rail vehicle can climb with all wheels powered is 25%. Also under those conditions if you started sliding, you were toast.
Roger Mitchell
Master Mechanic
Fort Collins Municipal Railway

n0mcr@netzero.net