For any type of train or railcar on any type of railway, be it mainline freight or light rail, what are typically the respective minimum rollaway gradients when all brakes are fully released and no power is applied, in the absence of any external forces besides gravity and friction such as wind, seismic activity, or other objects pushing or pulling on it? If you have any personal experience, please also comment.
Most mainline railroads (more accurately railways) and metros in the world limit the exceptional maximum gradient to 1% = 1:100 at station platforms, with 0.5% = 1:200 being the normal maximum, 0.35% = 1:285.7̅1̅4̅2̅8̅5̅ being the preferred maximum (which is also the standard minimum in underground and aerial structures for drainage purposes for the WMATA Metrorail), and 0.3% = 1:333.3̅ being the normal minimum in underground and aerial structures (including stations) for drainage purposes for some of the other metro systems. Most light rails and monorails limit the exceptional maximum gradient to 2% = 1:50 at station platforms, with 1% = 1:100 being the normal maximum, 0.5% = 1:200 being the preferred maximum (which is also the standard minimum for Sound Transit Link), and 0.3% = 1:333.3 being the normal minimum in underground and aerial structures (including stations) for drainage purposes.
Most mainline railways limit the exceptional maximum gradient in parking and coupling/decoupling areas to 0.25% = 1:400, with the normal maximum being 0.2% = 1:500 and the preferred maximum being 0.1% = 1:1000, with India Railways even limiting the preferred maximum to 1/1200 = 0.083̅ %. Most metros limit the exceptional maximum gradient to 0.5% = 1:200 in parking and coupling/decoupling areas, with 0.3% = 1:333.3̅ being the normal maximum and the preferred maximum being 0.15% = 1:666.6̅ or 1:660 = 0.1̅5̅ %, which are almost identical to each other. Most light rails and monorails limit the exceptional maximum gradient to 0.5% = 1:200 in parking and coupling/decoupling areas, with 0.3% = 1:333
Correct. The train approached the top of the grade at track speed (80 mph), and only then did the engineer discover that the brakes were not working properly.
Personal experience - loaded cars on a 0.3% grade will accelerate to 5 or 6 mph in a few hundred feet from gravity alone.
In new construction, you mean? Must be a number of US passenger stations on grades steeper than 1%. (Auburn, CA is 1.5%, and the passenger consist parks there overnight.)
Yards, you mean? No doubt lots of US yards are steeper than 0.25%. Do Dunsmuir and Keddie still count as “yards”? They’re both near 1%. Helper (on DRGW) is 0.6% or more; the steep parts of Grand Junction are too.
I doubt any rail car is light enough that it won’t start rolling on 0.5%. Any halfway-heavy car will accelerate to 100+ km/hr down 0.5%.
Far as anyone knows, a heavily-loaded freight car will maintain 20-30 km/hr rolling down 0.1%. None of us can tell you whether it will start rolling on 0.1% – it’s not that easy to learn whether it will, since you have to measure the grade with the car sitting on it.
Incidentally, the grade in NY Penn Station isn’t 0.4%. That may be the maximum, west of the station and east of the river tunnels, but they built the station itself leveler than that. No need for any grade, aside from drainage. If you want a passenger station on a 0.4% grade, Princeton Junction will do pretty well – it averages about 0.42% for the length of the platform. As I recall, a westward train there does roll backwards for a moment if the brakes release before the throttle is opened.
The B&O’s Riverside Yard at Locust Point in Baltimore Terminal was built on ground that was visually level. Yard crew was assigned to weigh on the track scale in Riverside yard a High Value heavyweight electrical transformer loaded on a 8 axle depressed center heavy duty flat car. Crew stopped with the engine on the West End of the car and the car centered on the track scale. When the engine cut away the car began to roll East from the Scale Track across the yard lead, across the Andre St. road crossing at the yard office and followed the tracks about 3/8 mile east of the yard office to the area of the crew room adjacent to the United Fruit Pier lead where yard engines were parked when not in use. The car struck engine 8410 a SW-1 and snapped the ‘front porch’ (a nominal 10 inch thick steel casting off the front of the engine from the force of the impact. Total distance that the car was rolling free was just slightly over 1/2 mile.
As soon as the car was seen rolling away on the scale, the crew attempted to mount it and apply the hand brakes - hand brakes which weren’t operative. Crew was disciplined for not applying and knowing that the brakes were effective before cutting the engine away on the scale. The transformer was inspected and sent back to the manufacturer for repairs/replacement. The engine was repaired and soldiered on for several more years.
This engineering/architectural diagram clearly shows grades of +0.4% and -0.4% within the station area, with no vertical curve between the positive and negative slopes. Also, with all of the limits, they are for new builds. And no, I do not mean yards only for parking and coupling/decoupling areas, because passenger trains may also routinely be parked without anyone on board and coupled/decoupled at select tracks in select stations outside of yards.
But visually level is up to a 0.5% grade for continuous lengths, possibly up to 1% grade in the relatively short distances of a yard, so one can’t tell that it’s not truly level unless they have surveying equipment. I’ve been on station platforms that had a constant 1% longitudinal grade and it was visually level within the sightline (which didn’t extend beyond the station).
“parking and coupling/decoupling areas” for passenger trains, you mean? In the US?
As it happens, US passenger “parking areas” usually are fairly level, unlike the 1.5% at Auburn. How about the Albuquerque system? No idea where they park trains overnight, but I’ll bet some exceed 0.25%. Maybe some Chicago lines too? And New York and Philadelphia?
By the way: don’t waste time trying to figure out what “visually level” means.
Good luck finding a “minimum rollaway gradient” - won’t be found in print. Roller bearings, wind, derails and other practical reality variables determine what will be allowed in a practical sense. Even hump yard variables are different from place to place.
(one big variariable is how good (or bad) your operating employees are… ie what you are expected to do vs what is actually done.)
In my riding on the head end of trains - in many cases the only way to tell if there was a grade was to watch the load meter on the locomotive. If the load meter went up in amperage you were going up grade, if the amperage decreased you were going down grade. If you were hauling the train up grade the speed of the train decreased and if you were going down grade the speed of the train would increase. In looking at the terrain you could not tell up from down.
Yes, I meant passenger trains, because freight trains are never coupled or decoupled at station platforms. I was actually at Montgomery Street station in San Francisco, which serves BART (a real metro/subway) and MUNI Metro (not a metro, actually light rail transit). The station is underground with the mezzanine on top, MUNI Metro in the middle, and BART on the bottom. I’ve been on the mezzanine. The station is 700 feet long to accomodate 10-car BART trains, though the MUNI Metro platforms are shorter and are open to the BART level below at the ends and basically have the tracks suspended over the BART tracks at the passthroughs. Whenever I entered at east end of the mezzanine, I always felt like it looked like the wall on the other (west) end of the mezzanine was slightly higher, somewhere between 2 and 6 feet, according to the visual sightline from what my inner-ear canals feel is the horizontal, despite it always visually appearing to be completely flat if it weren’t for the input from my inner ear canals. However, human senses are often quite inaccurate and somewhat imprecise, especially with small values, so I dismissed it as my inner ear canals playing with me from being inaccurate. But then, one month ago or so, I suddenly decided to ask MUNI what the gradients (grades) in the subterranean stations were, via San Francisco’s Sunshine Ordinance, and they just replied to me around a week ago. They were very nice to actually give me the data. In the list, it showed that Montgomery Street station had a 1% upgrade from east to west. 1% over a 700 ft run means a 7 ft rise. It turns out, the station was indeed not level and my inner-ear canals were that sensitive (accurate and precise) to non-level slopes!
Yes, Dunsmuir and Keddie count as yards though. But why would yards be built at such a steep slope? Isn’t one of the secondary purposes of a yard to let trains that had brake failure to gradually come to a safe halt there (where it doesn’t block traffic on the line while it’s waiting to be rescued) or to store railcars that were towed there because of brake failure? Maybe Dunsmuir and Keddoe are rare exceptions, but still why are many other yards steeper than 0.25%? Also, why would they build stations steeper than 1%? Trains already struggle to maintain speed on 1%, and having to start again and accelerate to line speed after a stop there makes things much worse. Also, isn’t a secondary purpose of the stopping tracks of a station to act as a temporary refuge for a train (that is short enough to fit fully within it) with a severely weakened braking system (partial brake failure)?
How do you know that Princeton Junction is 0.42%? Also, does anyone here know what the grade(s) are through Newark Penn Station (elevated) for the NEC and/or PATH tracks? How about Philly 30th Street Station for the NEC (ground) and/or SEPTA Main Line (elevated)?
While I was doing some other work near Princeton Jct, years ago, I used the total station to get the difference in elevation between the ends of the north platform, and I assumed that just about equalled the difference at top of rail. Don’t think I checked the south platform.
I also checked Metuchen – as I recall it’s about 0.55%. According to the CNJ chart, Westfield is on 0.6%.