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| Scheduling Capacity (1353300) | |
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| (1353313) | |
Re: Scheduling Capacity |
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Posted by Stephen Bauman on Fri May 22 18:51:21 2015, in response to Scheduling Capacity, posted by BusRider on Fri May 22 17:09:43 2015. "Currently, 15 lines in the system cannot schedule any more service either due to having reached full track capacity, passenger capacity or both."Taking from an article on the MTA website regarding the new "Step Aside" signage on the floor of platforms. That's not true. It's an excuse used by the MTA to hide managerial decisions to keep down operational costs. The principal operational cost has been the elimination of split work shifts. (BTW, I'm in favor of eliminating split shifts as a safety measure.) However, it makes adding additional peak period trains more expensive than when more trains operated on the existing tracks with the same "obsolete" signal system. What determines the capacity? There are several components that determine capacity. Terminals are not usually a capacity determinant, except in NYC. This is due to bad design for newer reversing terminals like Jamaica Center and South Ferry. Reversing terminal capacity has been decreased because NYCT replaced faster acting electro-pneumatic switches with slower acting all electric ones. A reversing terminal's capacity is determined by the time it takes trains to traverse and clear the interlocking. The principal capacity component is intermediate capacity (between terminals). This is determined by the emergency braking distance. The idea is that the leader can stop in 0 time (derail or some other reason) and the follower must stop before colliding with the leader. This provision means the follower must maintain its emergency stopping distance behind the leader at all times regardless of the leader's speed. This means the follower must know in a timely manner its leader's position to a degree of precision and accuracy consistent with the operating tolerances of the emergency braking system. Intermediate stations add an additional wrinkle. Analytically, they are handled by assuming the leader is at the same distance ahead when the follower approaches the station. In order for that to happen the leader must have: slowed down to a stop from its station approach; spent dwell time within the station and accelerated ahead to a position that is greater than the follower's emergency braking distance. The principal parameters governing this are the service braking and acceleration rates, train length and the dwell time within the station. For most systems with standard braking and acceleration rates and a 30 second dwell time, the intermediate station capacity is a nominal 40 tph or 90 second headway. Uncertainty in locating the leader (block size or message delay for CBTC) increase this headway because this adds to the a longer safe distance between leader and follower. Longer trains increase the headway because the leader must travel further to reach the save distance from the follower. Headway should be the independent variable with dwell time being dependent on headway and not vice-versa. The shorter the period between trains, the fewer passengers there will be waiting to get on each train. When many lines share track. Merges are no different than interlockings leading to a reversing terminal. Let's assume merge interlocking is 300 feet long, trains are 600 feet long and trains travel at 10 mph over the interlocking. Trains must travel 900 feet to enter and clear the interlocking. If they travel at 10 mph, it will take them 60 seconds to clear the interlocking. If trains are scheduled every 120 seconds (30 tph), the interlocking would be idle for 60 seconds between trains. If trains were within 30 seconds of their schedule, then the leader being 30 seconds late and the follower 30 seconds early should not result in any delays at the merge point. Similarly, if trains were scheduled every 90 seconds (40 tph), trains would need to be within 15 seconds of schedule to guarantee no merging delays. |
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| (1353419) | |
Re: Scheduling Capacity |
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Posted by BusRider on Sat May 23 19:34:50 2015, in response to Re: Scheduling Capacity, posted by Stephen Bauman on Fri May 22 18:51:21 2015. So its still possible for 40tph? |
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| (1353433) | |
Re: Scheduling Capacity |
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Posted by Stephen Bauman on Sat May 23 21:10:50 2015, in response to Re: Scheduling Capacity, posted by BusRider on Sat May 23 19:34:50 2015. So its still possible for 40tph?Anything is possible. A more appropriate question would be if the TA had the personnel and operating equipment could they operate at the maximum service levels they did in 1954? The answer to that question is yes with the possible exception of the BMT Eastern Division and the Flushing Line. The problem is eastern end terminal capacity. The Atlantic Ave and Liberty Avenue terminals have been removed. The Flushing Line's problems concern the extension to the Westside Yards should that ever become operational. The 1954 maximum service level rates were approximately 25-33% greater than the rates that are currently operated. |
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| (1353435) | |
Re: Scheduling Capacity |
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Posted by BusRider on Sat May 23 21:37:30 2015, in response to Re: Scheduling Capacity, posted by Stephen Bauman on Sat May 23 21:10:50 2015. The Eastern Division, consisting of the J/Z, L, and M lines correct? |
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| (1353436) | |
Re: Scheduling Capacity |
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Posted by Stephen Bauman on Sat May 23 21:52:07 2015, in response to Re: Scheduling Capacity, posted by BusRider on Sat May 23 21:37:30 2015. The Eastern Division, consisting of the J/Z, L, and M lines correct?That's correct. The principal problems will be with the L and J/Z because of eastern terminal elimination. They also eliminated the Canal St terminal on the western end. However, the Chrystie St. connection makes up for that loss. |
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| (1353438) | |
Re: Scheduling Capacity |
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Posted by BusRider on Sat May 23 21:59:14 2015, in response to Re: Scheduling Capacity, posted by Stephen Bauman on Sat May 23 21:52:07 2015. So being those particular stations are gone, there's no other places to turn trains around to add the additional trains? |
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| (1353441) | |
Re: Scheduling Capacity |
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Posted by Stephen Bauman on Sat May 23 22:41:36 2015, in response to Re: Scheduling Capacity, posted by BusRider on Sat May 23 21:59:14 2015. So being those particular stations are gone, there's no other places to turn trains around to add the additional trains?The quick solution for a terminal limiting a line's capacity is to have multiple terminals. The Canarsie terminal would have to handle all the previous traffic from the 14th St-Canarsie, 14th St-Fulton and Broadway Short lines. |
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| (1353442) | |
Re: Scheduling Capacity |
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Posted by BusRider on Sat May 23 22:45:25 2015, in response to Re: Scheduling Capacity, posted by Stephen Bauman on Sat May 23 22:41:36 2015. I'm not familiar with those services, how many trains were that? |
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| (1353443) | |
Re: Scheduling Capacity |
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Posted by Stephen Bauman on Sat May 23 22:56:01 2015, in response to Re: Scheduling Capacity, posted by BusRider on Sat May 23 22:45:25 2015. The 14th St-Canarsie Line is today's L train. It ran from 8th Ave to Canarsie (Rockaway Pkwy) 6 tph. The 14th St-Fulton St Line ran from 8th Ave to Lefferts Blv over the Fulton St El from Atlantic to Lefferts 6 tph. The Broadway Short Line ran from Canal St to Atlantic Ave and provided local service that's now provide by the J/Z and M 8 tph. |
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| (1353445) | |
Re: Scheduling Capacity |
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Posted by randyo on Sat May 23 23:12:14 2015, in response to Re: Scheduling Capacity, posted by Stephen Bauman on Sat May 23 21:10:50 2015. One of the problems in in creasing capacity is the change in work rules that took place around 1970. Prior to that, M/M were allowed to key by red automatic signals as they were following trains especially when entering stations. Due to a couple of rear end collisions in which the M/M failed to operate their trains with the “restricted speed and extreme caution” as required by the rules, M/M were required to contact the command center for permission to key by but along with this rule was the requirement that M/M had to wait 3 min before radioing for such permission. As a result of now having to wait for completely clear signals before following trains could close in on their leaders entering stations since the signals would usually clear before 3 min, the high frequency of service of prior years was no longer possible. |
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| (1353453) | |
Re: Scheduling Capacity |
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Posted by Stephen Bauman on Sun May 24 00:32:19 2015, in response to Re: Scheduling Capacity, posted by randyo on Sat May 23 23:12:14 2015. Any procedure change regarding the key-by practice is not germane to the scheduling capacity question for three reasons.First, the follower never sees a red signal to key by. This should be obvious from my description of how far ahead the leader must be when the follower approaches a station entrance. It's the leader's time ahead of the follower that's the principal headway component aside from dwell time. Second, approaching a station to a stop at restricted speed and extreme caution increases the follower's stopping time. Keying-by increases headway and decreases service level capacity. Third, the practice of keying-by for "facilitating rush hour traffic" was outlawed by the Transit Commission on May 1, 1929. Any later change in the procedure on how the TA implemented keying-by referred to permissible uses of keying-by by the Transit Commission's 1929 order. The Transit Commission order permitted keying-by for "1. If the signal system be out of order. 2. If the movement of the train be necessary to safeguard life and or property." Neither of these conditions are consistent with normal operation at service level capacity. |
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| (1353482) | |
Re: Scheduling Capacity |
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Posted by Broadway Lion on Sun May 24 07:57:34 2015, in response to Re: Scheduling Capacity, posted by Stephen Bauman on Sat May 23 21:10:50 2015. Braking capacities of trains have changed. They are heavier, and what with composition brakes they do not stop as quickly. Rather than space the signals out more, they simply slowed the trains down. Actually, according to the LION \, it would have been no big problem to install emergency track brakes on the equipment to permit quicker emergency stops allowing trains to operate at higher speeds.Still, if the (R) train were to run Astoria to Fort Hamilton, all of its switches could be fleeted, and CBTC could be installed to allow saturation operation. The (Q) as we know, will run the SAS, and the (N) will go to Forest Hills via the 63rd Street Tunnel. The (R) gets all of the local tracks in Manhattan and Brooklyn to itself. Yeah I know about the yard issues, and there are many was to skin that cat so LION will not accept that as an issue. ROAR |
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| (1353490) | |
Re: Scheduling Capacity |
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Posted by Stephen Bauman on Sun May 24 10:44:10 2015, in response to Re: Scheduling Capacity, posted by Broadway Lion on Sun May 24 07:57:34 2015. Braking capacities of trains have changed. They are heavier, and what with composition brakes they do not stop as quickly. Rather than space the signals out more, they simply slowed the trains down. Actually, according to the LION \, it would have been no big problem to install emergency track brakes on the equipment to permit quicker emergency stops allowing trains to operate at higher speeds.Emergency braking rates have been specified at 3.2 mph/sec for all post WWII equipment. This means that all equipment going at equal speeds is designed to stop within the same distance, regardless of their weight or brake shoe composition. Whether the TA maintains their equipment to this design standard is another matter. The NTSB tests following the Williamsburg Bridge collision showed emergency brakes performing at less than half their design specification. Emergency braking rates don't have as much an effect on capacity as do service braking and acceleration rates. The emergency braking rate sets the safe stopping distance between trains. This distance is given by: d = (0.5*v^2)/a, where d is the safe stopping distance, v the velocity and a the emergency braking rate. A train moving at 25 mph would stop within 144 feet with an emergency braking rate of 3.2 mph/sec. An emergency braking rate of 6.4 mph/sec would stop that same train in 72 feet. It takes a train traveling at 25 mph only 1.9 seconds to travel those 72 feet. That's the potential headway reduction of only 1.9 seconds. It's not worth retrofitting the system because current service levels are way below capacity. N.B. these calculations did not include the 30% safety factor that is used for signal system design. Service braking rates are used to stop trains in stations under normal operating conditions. The service level braking rate for post WWII equipment has been 3.0 mph/sec. The braking time from 25 mph accounts for 8 seconds of the headway and covers 153 feet. The train will travel 447 feet within the 600 foot long station at 25 mph for a total of 12 seconds before applying the brake. This accounts for 20 seconds of the headway. Higher speeds may make for a quicker journey but after a certain point they increase minimum headway. The sweet spot is around 25 mph, given current service level braking and acceleration rates, dwell time and train lengths. Systems that operate at significantly higher speed do not approach even NYC's anemic service levels. CBTC could be installed to allow saturation operation. CBTC nor any other traffic control system (collision avoidance) does not increase capacity. The differences in traffic control system performance result from reaction time and the accuracy in locating trains. The reaction time savings is minimal between CBTC and today's antiquated relay based signal system. Short block lengths at station approaches make location accuracy comparable where it is needed. CBTC might raise capacity in the 60th St Tunnel from 40 tph to 42 tph. However, they are currently operating only 20 tph peak. |
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| (1353551) | |
Re: Scheduling Capacity |
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Posted by BusRider on Sun May 24 21:06:35 2015, in response to Re: Scheduling Capacity, posted by randyo on Sat May 23 23:12:14 2015. So really its all a modern signaling issue which slows the frequency of service down not the amount of space on trackage. |
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| (1353552) | |
Re: Scheduling Capacity |
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Posted by SelkirkTMO on Sun May 24 21:22:34 2015, in response to Re: Scheduling Capacity, posted by BusRider on Sun May 24 21:06:35 2015. Worse than signalling. It's management. |
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| (1353554) | |
Re: Scheduling Capacity |
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Posted by BusRider on Sun May 24 21:25:35 2015, in response to Re: Scheduling Capacity, posted by SelkirkTMO on Sun May 24 21:22:34 2015. There has to be a way though to keep higher ups happy with money savings but provide adequate service. |
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| (1353557) | |
Re: Scheduling Capacity |
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Posted by SelkirkTMO on Sun May 24 21:48:55 2015, in response to Re: Scheduling Capacity, posted by BusRider on Sun May 24 21:25:35 2015. It's more a thing of the blame game. Somebody screws up and overkill takes its place. Massive overkill. Normally in many other places, retraining and ENSURING that the rules are known and compiled with is sufficient. Here, the rules get changed instead. Fail. |
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| (1353819) | |
Re: Scheduling Capacity |
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Posted by BusRider on Tue May 26 18:16:09 2015, in response to Re: Scheduling Capacity, posted by randyo on Sat May 23 23:12:14 2015. Question for randyo: When service was more frequent, was it harder to generate work programs with lunch breaks and various service? patterns? |
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| (1353827) | |
Re: Scheduling Capacity |
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Posted by randyo on Tue May 26 18:51:20 2015, in response to Re: Scheduling Capacity, posted by BusRider on Tue May 26 18:16:09 2015. Not really. The rule of thumb was that all crews should make at least one rush hour trip and any crew that didn’t was a “wasted” crew. Of course some lunch breaks did have to be scheduled during rush hours, but in general, there were very few runs that didn’t make a rush hour trip. There were always some exceptions to that rule. For example, Woodlawn had a late PM run that started around 800PM and finished around 4500PM but that was unusual. |
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| (1353835) | |
Re: Scheduling Capacity |
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Posted by BusRider on Tue May 26 19:05:43 2015, in response to Re: Scheduling Capacity, posted by randyo on Tue May 26 18:51:20 2015. Were runs always grouped by time starting like Midnight, Day, and PM/Evening? |
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| (1353959) | |
Re: Scheduling Capacity |
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Posted by randyo on Wed May 27 17:37:05 2015, in response to Re: Scheduling Capacity, posted by BusRider on Tue May 26 19:05:43 2015. They have been since I’ve been aware of scheduling procedures at least on the NYCTS. I believe CTA doesn’t group runs by classification but puts all the day off combinations in one big pool within the respective districts. NYCTA groups runs 2 ways, by district and by classification. Train crews pick within districts and can in the event S/S RDOs are unavailable, the weekend pieces from any line within the district can be added to the run to complete the 5 day work week. In the case of RDO relief runs, it could be possible for an employee to have a run on a different line every day as long as the lines are within the district. As far as classification id concerned, the runs are broken down by classification as to AM, PM or midnight. Runs reporting between 2200 hrs and 0359 are considered midnight runs. Runs reporting between 0400 and 1159 are considered AM runs and runs reporting between 1200 and 2159 are considered PM runs. Weekend pieces and other pieces that are part of RDO relief runs can only be put together within the appropriate time classification thus if an employee has an AM run during the week, he/she can only pick an AM run on the weekend assemble the full work week. In places like Chicago that don’t group runs by time classification, employees can combine AM or PM runs as long as there is sufficient rest time between them. Personally, I feel that the NYCTA system is fairer since under the CTA setup, it is theoretically possible for all the S/S off combinations to be picked by the senior AM employees leaving midnight and PM employees wit only weekdays off. In NY an employee who can’t pick weekends off on am AM run van usually get a weekend off by picking a late midnight or early PM run rather than having the senior AM employees hog all the weekends off. Also while NYCTA employees can pick their days off independently of the run and assemble RDO reliefs from available weekday pieces, many transit properties including NYCTA Bus have packaged runs in which the days off are constant for each run and in order to change RDOs employees have to pick different rune. RDO reliefs under that system are also packaged rather than left to the discretion of the individual employee. |
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| (1353973) | |
Re: Scheduling Capacity |
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Posted by Southern BMT on Wed May 27 20:14:07 2015, in response to Re: Scheduling Capacity, posted by randyo on Wed May 27 17:37:05 2015. I remember hearing that picking districts had changed a few years ago. Which lines are grouped together now? |
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| (1353976) | |
Re: Scheduling Capacity |
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Posted by BusRider on Wed May 27 20:57:01 2015, in response to Re: Scheduling Capacity, posted by randyo on Wed May 27 17:37:05 2015. Interesting, thanks for the insight. Back then, being routes are grouped into district was it easier being work was done by hand for the most part, allowing lunches and layovers be considered more easily? |
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| (1354080) | |
Re: Scheduling Capacity |
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Posted by randyo on Thu May 28 13:22:33 2015, in response to Re: Scheduling Capacity, posted by Southern BMT on Wed May 27 20:14:07 2015. The districts have changed many times over the years and right now I’m not sure what the current ones are. |
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| (1354081) | |
Re: Scheduling Capacity |
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Posted by randyo on Thu May 28 13:28:40 2015, in response to Re: Scheduling Capacity, posted by BusRider on Wed May 27 20:57:01 2015. The same standards that we used for scheduling by hand were incorporated into the computer programs, so I didn’t see much difference. While the schedules and work programs were prepared by the Operations Planning Dept, the grouping of the districts, days off and RDO relief jobs was done by the RTO Pick office. The only packaged jobs that O/P did were those for the tower operators and supervision. Those are the only groups of employees that have packaged jobs, days off and relief jobs that I mentioned in my other post. |
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| (1354369) | |
Re: Scheduling Capacity |
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Posted by BusRider on Fri May 29 20:14:37 2015, in response to Re: Scheduling Capacity, posted by randyo on Thu May 28 13:28:40 2015. When you were creating them what lines were grouped? Was it easier to schedule by group being the various service patterns, frequencies and specific number of cars for the time of day become difficult at all? |
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| (1354483) | |
Re: Scheduling Capacity |
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Posted by randyo on Sat May 30 19:18:44 2015, in response to Re: Scheduling Capacity, posted by BusRider on Fri May 29 20:14:37 2015. The schedule Dept didn’t group the lines either when it was in RTO or after it went into O/P. The schedule section wrote the timetables and work programs and the RTO pick office and division supts and later the ACTOs decided on which groups the respective lines would be assigned to. |
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| (1354537) | |
Re: Scheduling Capacity |
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Posted by BusRider on Sun May 31 15:39:21 2015, in response to Re: Scheduling Capacity, posted by randyo on Sat May 30 19:18:44 2015. Oh okay thanks. I might have asked this before but with the various services back then how much interlining were there? I remember you mentioning the AA/B and QJ/M/RR. |
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| (1354544) | |
Re: Scheduling Capacity |
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Posted by randyo on Sun May 31 16:35:18 2015, in response to Re: Scheduling Capacity, posted by BusRider on Sun May 31 15:39:21 2015. The only true interlining was between the AA/B, and at first the QJ/QB/RJ. After the first post Chrystie pick, the RR Nassau St service interlined with the RR and not the QJ. When the M was sent to Stl in place of the QJ, the M and QB then interlined although as I mentioned in another post, elected QB intervals interlined with the RR and some selected RR/Nassau intervals interlined with the M but not quite to the same extent that the AA/B and M/QB interlined. Over the years, other interlining was done with the N and B on weekends but that didn’t last too long since a delay on one line might cause a delay on another if an interlined crew was delayed ann unable to make their trip. The other most common interlining was between the RR and GG in which a Rr crew arriving at Ctl would either make a GG trip out of Ctl or deadhead to Qns Plz for a GG trip after the GGs stopped running to Ctl. One of the oddest interlining between the GG and RR was a RR crew reporting at City Hall and staging what was referred to as a “manned gap train.” The train would be spotted during the PM rush hour in City Hall Yd and be made available for either the N or RR in either direction if either line encountered a big delay in service. After the rush hour if the train were used, the crew would somehow make it back to Ctl or if the train were not used, run light to Cll and if there were time, lay up the train and deadhead to Qns Plaza for a GG trip. Although it’s been a while since I did any of those, I recall that most of the RR/GG interlined runs were incorporated into the RR work program rather than the GG. |
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| (1354550) | |
Re: Scheduling Capacity |
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Posted by BusRider on Sun May 31 17:50:17 2015, in response to Re: Scheduling Capacity, posted by randyo on Sun May 31 16:35:18 2015. Interesting thank you! When making the schedules/work programs were those trips build first to alleviate confusion on paper and better allocate layovers?Also, when a line was express in one area or at one time period but local in other or somewhere else how did you add up running times? I remember you saying at night and weekends an empty train would be used I believe to get an accurate time. |
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Re: Scheduling Capacity |
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Posted by randyo on Sun May 31 18:59:41 2015, in response to Re: Scheduling Capacity, posted by BusRider on Sun May 31 17:50:17 2015. The running times just fell into place depending on where the trains ran in what classification of service. |
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