My Slant on SEPTA

Riding on the Warminster line, I'm familiar with slanted tracks. Think the Roslyn stop with a good tilt towards the parking lot below, to the
west.

That's all well and good, seems stable.

But on the past few days, I noted a slowdown between Fernrock (And a bit before that if there is a slight backup) to well past Wayne junction. I figured that it was a backup, and once we got past the Roberts yard facility.

But today (Saturday) my train was going at a rather slow speed out of Fernrock. So there, I think about possible Fox Chase run that was off time and we had to slow down to allow them to pass before us onto the track.

So there we were going slowly, and I'm thinking, are we slanted? Do I remember being slanted here before, perhaps slanted a long time and I didn't notice?

Only a Warminster rider would appreciate the Roslyn comparison, but I'm sure other lines have a spot with considerable slant/tilt.
Has anyone else noted this on segment of track just past Fern Rock but before the switches for Fox Chase?
Maybe its banked for speed and I never noticed as I have not gone slow on that one segment.

Just wondering. I thought maybe we were going slow for a speed restriction, if it wasn't a slowdown for the Fox Chase.

Do you understand the concept of superelevation?

AKA, banking. yes, very much. I just never noticed it there (Fern Rock) till we took that section of track slowly, yesterday. Today, after 4 days, they did that section of track full speed and it felt perfectly normal. So I wrote it off to just banking a section of track for a slight curve for high speed. I also looked at a map after I posted and saw a curve where that bank would be appropriate.



Roslyn, on the other hand, that is not superelevation/banking. There IS a slight curve there going north of the station. I've been on this line long enough that I saw thing through the track work at Roslyn a few years ago. I think that is all just sagging towards the general downhill towards the west, enhanced by the later digging out the soil for Giant supermarket parking lot. I don't think anyone was running passenger/freight thru that area, past,present,future that would justify that slant.

ON superelevation, there is probably more nuance than the term 'banking'. Probably banking with additional computations for center of gravity, involving weight of traincars, speed . . .

Thanks

The more nuanced term IS superelevation, and the exact amount of "bank'' is prescribed by how fast you want that maximum curve speed to be per an FRA regulated maximum speed for the curve in relation to the superelevation. There are FRA max limits for superelevation depending on certain conditions.

Roslyn is in fact superelevated, and yes you do "feel" it more the slower you go as the whole point of it is to better balance the centrifugal force that occurs when going faster through a curve. When you're going close to that max speed, those opposing forces are closer to equal and you don't feel either so much. If the grade at Roslyn did simply slope that way naturally and SEPTA didn't want so much superelevation, they would regrade it that way. In this case, it's superelevated in the station because the curve is so long and runs beyond the station, so you need to match the superelevation throughout. Going from moderate to no superelevation within the same curve is generally a no-no.

The vast majority of curves on passenger railroads are in fact superelevated, even if at a barely perceptable 1/2".

Check your train schedule. Some of these trains have 5 minutes between Fern Rock and Wayne Junction.

No doubt schedule padding for the (failed) anticipation of the PTC cutover on Warminster Line trains.

If your train is on time, the engineer goes slow to burn off the extra schedule time between Fern Rock and Wayne Junction. If he is running late, then he can run maximum speed to play catch-up with the schedule.

The same happens with Doylestown / West Trenton trains between Fern Rock and Jenkintown. If they don't stop at Melrose or Elkins, they have 7 or 8 minutes to run 4 miles.