Nostalgia & History > Question about TT&TO ops

What part of the puzzl am I missing?

Trains are allowed to arrive at stations early, but must not leave early. A westbound passenger is due at station A a 6 a.m. An eastbound extra is running also to station A and sees that it can arrive there and clear in the westbound passenger in time. The passenger was able to slow roll 2 flagstops due to no passengers on the platform and therefore is now 20 minutes early. What prevents a collision when the exta arrives "A" and the passenger is already there?

Thanks for helping a TTTO newbie understand.

dave

puddlejumper Wrote:
-------------------------------------------------------
> Trains are allowed to arrive at stations early,
> but must not leave early. A westbound passenger
> is due at station A a 6 a.m. An eastbound extra
> is running also to station A and sees that it can
> arrive there and clear in the westbound passenger
> in time. The passenger was able to slow roll 2
> flagstops due to no passengers on the platform and
> therefore is now 20 minutes early. What prevents
> a collision when the exta arrives "A" and the
> passenger is already there?

Your example requires a siding at Station X for the extra to clear in - the extra cannot occupy the main once it arrives at Station X. If there were no siding, the extra would have to wait farther west.

So the EB extra is advancing against a scheduled WB, and knows that it has to be in the clear by 5:55.

The WB scheduled train arrives at Station X at 5:40. It is not allowed to pass the train order board until 6:00.

The EB extra arrives at the west end of Station X Siding, enters the siding prior, and relines the switch to normal prior to 5:55.

The WB scheduled train departs at 6:00, and the EB extra departs the east end of Station X Siding shortly after.

---

> The passenger was able to slow roll 2
> flagstops due to no passengers on the platform and
> therefore is now 20 minutes early.

In your example there is a lot of schedule padding between the second flag stop and station A. Just because no one was at the first flag stop does not authorize the train to run early past the second flag stop. For that matter, depending on what the timetable says and what the rules of the particular railroad are, the train wouldn't necessarily be authorized to leave the second flag stop early even if no passenger was waiting there. You'd be pretty upset if you showed up at 5:43 for a train scheduled to make the second flag stop at 5:45 but the train had actually run past at 5:41.

In the example, the passenger trains tme applies at the clearance point of the west switch, not at the train order signal, so he may pass the signal unless it is displaying an indication requiring him to stop.

Implicit in the scenario described is that there are no train orders out there imposing any other restrictions upon the passenger train.

Also implied is that the extra will fit on the siding. If not (or if the station would be on the same side of the main as the siding and the extra won't fit without blocking the platform) the extras hind end would still occupy the main west of town, and would have to flag protect against the passenger train.

-John



Edited 2 time(s). Last edit at 04/15/14 07:43 by LarryDoyle.

The previous replies are good but I'll add a few things.

Every named point in a timetable is called a station. A regular train will be given a specific time for each station. The time is always the "leaving" time unless a separate "arriving" time is listed. A regular train cannot pass or leave early on any leaving time in the timetable. Train orders can modify or annul the schedule of a regular train but that is a separate discussion. As the other poster said, if a regular train finds no passengers at a flag stop it still cannot pass that station until the scheduled leaving time. In such a case, the train may have to stop and wait until time has expired even though there is no "work" at the station. The stop and wait scenario can happen anywhere there is a station time, even if the station is just a siding in the middle of nowhere. I have been on passenger trains in ABS where the crew quipped on the radio, "We're here two minutes early...slowing down." Indeed, for an on-time passenger train, the train may have to run at much less than the timetable maximum speed so as not to arrive at stations early. This is because there is recovery time (padding) built into the schedule. As a side note, I always wanted to be late riding the Santa Fe. An on-time run would be at "ho-hum" speeds but if the train was late, then all hell would break loose!

The time table image shows the difference in regular train schedules in CTC (TCS) and ABS territory. In CTC there is no timetable authority so no times are listed except for the passenger stops. In ABS most stations have a schedule time. And...yes the lonely station of Dennison, AZ...there is nothing there except sidings and tumbleweeds, but the engineer of an on-time No 18 still has to moderate his speed so as not to pass the station any earlier than 829AM. Two years after this timetable was published the track through Dennison was converted to CTC and the timetable time blanked. Under CTC rules, No 18's engineer could pass derelict Dennison without having to look at his watch.

Aside from the timetable rules, the example does not present a danger of collision as long as various other operating rules are followed. Even if the passenger train arrived at the meeting point a few minutes early, it can't leave until the scheduled time. The opposing extra knows it has to clear the passenger on the passenger train's time and would do so at a station according to the clearing time rules.

Bob

---

Western RRs usually stuck to unmodified
Rule 92 (or whatever)-- no train could leave
any station ahead of time. But NY Central and
PRR, at least, allowed trains on Rule-251
double track to run ahead of time at stations
where they wouldn't receive traffic.

Thank you all for your replies. As I thought, I was missing a few factors that all make sense to me now.
Dave

johnacraft Wrote:
-------------------------------------------------------
> Your example requires a siding at Station X for
> the extra to clear in - the extra cannot occupy
> the main once it arrives at Station X.

Actually, the extra could occupy the main between the switches until 5 minutes before the time on the passenger train at the next station east. For example, he has ample time and has a setout to make which would require use of the main.

It is even allowable for the extra to use the main track east of the east switch until 5 minutes before the time shown for the westbound at the next station to the east. The extra could even back into the siding under these circumstances. (If necessary to back in and the extra is working on the time of the westbound, flag protection would be required.)

> If there
> were no siding, the extra would have to wait
> farther west.
>
> So the EB extra is advancing against a scheduled
> WB, and knows that it has to be in the clear by
> 5:55.
>
> The EB extra arrives at the west end of Station X
> Siding, enters the siding prior, and relines the
> switch to normal prior to 5:55.
>
> The WB scheduled train departs at 6:00, and the EB
> extra departs the east end of Station X Siding
> shortly after.

Once the passenger westbound has cleared the east switch, the extra may depart eastward even if it is before 6:00. However if the westbound is late the extra must remain clear of the main from 5:55 until the westbounds markers clear the east switch, or for 12 hours, or until receiving a Train Order restricting the westbound to allow the extra to advance - whichever occurs first.

-John

The example timetable might be a bit misleading. The subdivision shown (Seligman to Winslow) was double track and 251 territory, so an opposing extra would not have been concerned with opposing trains in current of traffic. Well nuts, I just made this more complicated than it really is. A Eastward extra would only clear following trains as directed by the train dispatcher.

Norm

Norman Orfall
Helendale, CA
TIOGA PASS, a private railcar