Push-Pull Vs EMUs?

I feel like this question probably covers an area more broad than NJ transit itself, and if there is a better place for this thread, feel free to move it.

What is the advantages and disadvantages of Push-pull train sets compared to electric multiple units? Why not DMUs instead of of diesel powered trains?

I was under the impression that MUs cost more to use and maintain than a locomotive hauled train, but then some people argued that the savings of a locomotive hauled set weren't that significant.


I have no position on this myself, I just was curious what the reasoning was.

I once heard that NJT did a study and found the EMU were economically best for 7-and-under cars, while locomotive-hauled was better for above. This was maybe ten years ago so things change.

green_elite_cab wrote:I feel like this question probably covers an area more broad than NJ transit itself, and if there is a better place for this thread, feel free to move it.

What is the advantages and disadvantages of Push-pull train sets compared to electric multiple units? Why not DMUs instead of of diesel powered trains?

I was under the impression that MUs cost more to use and maintain than a locomotive hauled train, but then some people argued that the savings of a locomotive hauled set weren't that significant.


I have no position on this myself, I just was curious what the reasoning was.

In terms of NJT specifically, all that I've read here on the site says arrows can keep a local schedule more easily despite the lower speed limit for their operation, and they can be 12 cars whereas push pull is typically maxed at 10. One thing I do know, is that in most cases the push pull cars need some form of outside power (locomotive or yard plug) to keep the environment inside from getting too hot or cold, whereas the arrows just sit with pantos up and they are all set.

The trend with NJT seems to be favoring push-pulls, so I am not sure the conversation about the arrows' current use will have a lot more time left to it. There was some mention of an MLV based EMU, but that is well beyond my knowledge base.

TrainPhotos wrote:

green_elite_cab wrote:I feel like this question probably covers an area more broad than NJ transit itself, and if there is a better place for this thread, feel free to move it.

What is the advantages and disadvantages of Push-pull train sets compared to electric multiple units? Why not DMUs instead of of diesel powered trains?

I was under the impression that MUs cost more to use and maintain than a locomotive hauled train, but then some people argued that the savings of a locomotive hauled set weren't that significant.


I have no position on this myself, I just was curious what the reasoning was.

In terms of NJT specifically, all that I've read here on the site says arrows can keep a local schedule more easily despite the lower speed limit for their operation, and they can be 12 cars whereas push pull is typically maxed at 10. One thing I do know, is that in most cases the push pull cars need some form of outside power (locomotive or yard plug) to keep the environment inside from getting too hot or cold, whereas the arrows just sit with pantos up and they are all set.

The trend with NJT seems to be favoring push-pulls, so I am not sure the conversation about the arrows' current use will have a lot more time left to it. There was some mention of an MLV based EMU, but that is well beyond my knowledge base.

I Agree on the EMU Keeping a local schedule i will say riding on the push-pulls the speed pick up is not as fast i dont think compared to a EMU ???? or so it feels like it. But push-pulls holds more people ,EMU'S seem to accelerate a bit more and not to much weight. NJT does seem to favor push-pulls ...but i still think both fleets are very very reliable and fine to have. '
I've seen as many as 10-13 EMU's rather it be a express or local, limited train. A MLV emu would be interesting to see how they fair on NJT It would look so weird to me but hey whatever works....and isn't there something about the locomotives and EMU's having different inspection timelines or something like that and the cost ?

TrainPhotos wrote:

green_elite_cab wrote:I feel like this question probably covers an area more broad than NJ transit itself, and if there is a better place for this thread, feel free to move it.

What is the advantages and disadvantages of Push-pull train sets compared to electric multiple units? Why not DMUs instead of of diesel powered trains?

I was under the impression that MUs cost more to use and maintain than a locomotive hauled train, but then some people argued that the savings of a locomotive hauled set weren't that significant.


I have no position on this myself, I just was curious what the reasoning was.

In terms of NJT specifically, all that I've read here on the site says arrows can keep a local schedule more easily despite the lower speed limit for their operation, and they can be 12 cars whereas push pull is typically maxed at 10. One thing I do know, is that in most cases the push pull cars need some form of outside power (locomotive or yard plug) to keep the environment inside from getting too hot or cold, whereas the arrows just sit with pantos up and they are all set.

The trend with NJT seems to be favoring push-pulls, so I am not sure the conversation about the arrows' current use will have a lot more time left to it. There was some mention of an MLV based EMU, but that is well beyond my knowledge base.

The MLV EMU is in the fleet replacement plan announced last year. That would change the game because of the seating capacity increase and fact that they're frequency-agile (i.e. no more Arrow and ALP-46 pu-pu platters around the NJCL's phase break and less of a need to supplement the EMU's with higher-capacity push-pull electrics at rush). But it's still undetermined what quantities they'll order of the new EMU's vs. quantities of coaches, though you would think EMU's as % of total car fleet would start to swing back up somewhat just on replenishments for attrition. The ALP-46's certainly aren't going away, and if NJT is the tenant railroad paying Amtrak's high electric rates on the NEC they'd probably gerrymander the EMU's to their own lines and push-pulls to the NEC more often than not. Push-pull electrics do use less electricity than an EMU despite overall efficiency tilting EMUs' way. That does matter when held captive to an Amtrak that doesn't always play nice on rates (though I have no idea if NJT gets gouged as bad as MARC does on the D.C. end of the system that has less power capacity to give).

They both have advantages and disadvantages (electric or diesel)
Push-Pull
Advantages
The loco can be swapped out when it needs maintenance, at a different cycle to the passenger stock
Individual faulty cars can be removed or swapped out without taking the whole set out of service
Changes in length of the consist to suit changing requirements is easier
For diesel, no underfloor prime mover vibrations or noise for passengers
Disadvantages
Locomotive takes up platform room when consists get long and space is limited (not sure how much of an issue this is in the US, it is in the UK)
Although the total weight of a consist is probably much the same, the weight of the loco is concentrated in on place, thus causing more track wear (this pushes the cost of operating Push-Pull in the UK, as the track access charges for a loco+unpowered cars is far higher than for the equivalent number of MU cars)
Loco is a single point of failure, if that dies, the train can't move
MU
Advantages
All vehicles can carry passenger, no 'dead' train length
Less track wear due to better spread of weight
Distributed traction means better resiliency, if one fails the unit can normally limp home using the others (more so with diesel than electric)
Can allow multiple unit working with end doors and diaphragms fitted
Diesels can save fuel by shutting down one or more engines when they are not needed.
Disadvantages
If one vehicle is faulty, the whole set is out of action
Diesel MUs provide a less comfortable passenger experience
Impossible to gradually extend or reduce train lengths to suit loadings short term, and harder long term too.

Performance is mainly down to the amount of power installed, however in very high power/speed cases, an MU will have more powered wheels to get adhesion

I'm sure other people can think of some others.

I've been commuting on DMUs of various types for over 10 years, and I still can't ignore the engine noise and vibration.
http://en.wikipedia.org/wiki/British_Rail_Class_220" onclick="window.open(this.href);return false;
http://en.wikipedia.org/wiki/British_Rail_Class_221" onclick="window.open(this.href);return false;
http://en.wikipedia.org/wiki/British_Rail_Class_222" onclick="window.open(this.href);return false;
http://en.wikipedia.org/wiki/British_Rail_Class_158" onclick="window.open(this.href);return false;

It was posted around here several years ago when NJT wanted to go all loco hauled and no emu because the arrows inspection cycle is like a locomotive at 30 days (I think) and unpowered cars have a 90 day inspection cycle (I think, again).

I guess the question is how much does it cost to do an inspection? If everything was locomotive hauled, how many inspectors can NJT get rid of?

kilroy wrote:It was posted around here several years ago when NJT wanted to go all loco hauled and no emu because the arrows inspection cycle is like a locomotive at 30 days (I think) and unpowered cars have a 90 day inspection cycle (I think, again).

I guess the question is how much does it cost to do an inspection? If everything was locomotive hauled, how many inspectors can NJT get rid of?

Not enough for it to matter. A locomotive's going to have a lengthier inspection than an EMU because it's a more complicated beast. Something like an ALP-45DP is going to have a lengthier inspection than an EMU because it's got so much more to inspect inside it. A large operation like NJT has so many cars that the scale of laying off a few inspectors is a drop in the bucket for the overall scale of the operations.

kilroy wrote:It was posted around here several years ago when NJT wanted to go all loco hauled and no emu because the arrows inspection cycle is like a locomotive at 30 days (I think) and unpowered cars have a 90 day inspection cycle (I think, again).

I guess the question is how much does it cost to do an inspection? If everything was locomotive hauled, how many inspectors can NJT get rid of?

The only reason they haven't is because of one or two branches that are meant for MU operation although one could, has, and does operate push-pulls and the other has a vocal group trying to keep NJT from converting it to a bus route (Two Arrow IIIs can hold a lot more then a transit bus).

F-line to Dudley via Park wrote:

TrainPhotos wrote:

green_elite_cab wrote:I feel like this question probably covers an area more broad than NJ transit itself, and if there is a better place for this thread, feel free to move it.

What is the advantages and disadvantages of Push-pull train sets compared to electric multiple units? Why not DMUs instead of of diesel powered trains?

I was under the impression that MUs cost more to use and maintain than a locomotive hauled train, but then some people argued that the savings of a locomotive hauled set weren't that significant.


I have no position on this myself, I just was curious what the reasoning was.

In terms of NJT specifically, all that I've read here on the site says arrows can keep a local schedule more easily despite the lower speed limit for their operation, and they can be 12 cars whereas push pull is typically maxed at 10. One thing I do know, is that in most cases the push pull cars need some form of outside power (locomotive or yard plug) to keep the environment inside from getting too hot or cold, whereas the arrows just sit with pantos up and they are all set.

The trend with NJT seems to be favoring push-pulls, so I am not sure the conversation about the arrows' current use will have a lot more time left to it. There was some mention of an MLV based EMU, but that is well beyond my knowledge base.

The MLV EMU is in the fleet replacement plan announced last year. That would change the game because of the seating capacity increase and fact that they're frequency-agile (i.e. no more Arrow and ALP-46 pu-pu platters around the NJCL's phase break and less of a need to supplement the EMU's with higher-capacity push-pull electrics at rush). But it's still undetermined what quantities they'll order of the new EMU's vs. quantities of coaches, though you would think EMU's as % of total car fleet would start to swing back up somewhat just on replenishments for attrition. The ALP-46's certainly aren't going away, and if NJT is the tenant railroad paying Amtrak's high electric rates on the NEC they'd probably gerrymander the EMU's to their own lines and push-pulls to the NEC more often than not. Push-pull electrics do use less electricity than an EMU despite overall efficiency tilting EMUs' way. That does matter when held captive to an Amtrak that doesn't always play nice on rates (though I have no idea if NJT gets gouged as bad as MARC does on the D.C. end of the system that has less power capacity to give).

What's a pu-pu platter?

keyboardkat wrote:

F-line to Dudley via Park wrote:

TrainPhotos wrote:

green_elite_cab wrote:I feel like this question probably covers an area more broad than NJ transit itself, and if there is a better place for this thread, feel free to move it.

What is the advantages and disadvantages of Push-pull train sets compared to electric multiple units? Why not DMUs instead of of diesel powered trains?

I was under the impression that MUs cost more to use and maintain than a locomotive hauled train, but then some people argued that the savings of a locomotive hauled set weren't that significant.


I have no position on this myself, I just was curious what the reasoning was.

In terms of NJT specifically, all that I've read here on the site says arrows can keep a local schedule more easily despite the lower speed limit for their operation, and they can be 12 cars whereas push pull is typically maxed at 10. One thing I do know, is that in most cases the push pull cars need some form of outside power (locomotive or yard plug) to keep the environment inside from getting too hot or cold, whereas the arrows just sit with pantos up and they are all set.

The trend with NJT seems to be favoring push-pulls, so I am not sure the conversation about the arrows' current use will have a lot more time left to it. There was some mention of an MLV based EMU, but that is well beyond my knowledge base.

The MLV EMU is in the fleet replacement plan announced last year. That would change the game because of the seating capacity increase and fact that they're frequency-agile (i.e. no more Arrow and ALP-46 pu-pu platters around the NJCL's phase break and less of a need to supplement the EMU's with higher-capacity push-pull electrics at rush). But it's still undetermined what quantities they'll order of the new EMU's vs. quantities of coaches, though you would think EMU's as % of total car fleet would start to swing back up somewhat just on replenishments for attrition. The ALP-46's certainly aren't going away, and if NJT is the tenant railroad paying Amtrak's high electric rates on the NEC they'd probably gerrymander the EMU's to their own lines and push-pulls to the NEC more often than not. Push-pull electrics do use less electricity than an EMU despite overall efficiency tilting EMUs' way. That does matter when held captive to an Amtrak that doesn't always play nice on rates (though I have no idea if NJT gets gouged as bad as MARC does on the D.C. end of the system that has less power capacity to give).

What's a pu-pu platter?

When a train has a mix of comet 2, 4, and 5?

It seems the mixed single level consists are either on NYP service or Bay Head diesels. Hoboken division diesels are solid Comet V (barring some exceptions).

R36 Combine Coach wrote:It seems the mixed single level consists are either on NYP service or Bay Head diesels. Hoboken division diesels are solid Comet V (barring some exceptions).

Why is this?

I was on a Long-Branch-NY morning train the other day, which had six MLVs and an ALP46 pushing. The engineer had the front vestibule open, and I took advantage of it until a lady collector closed it. But when the engineer pegged the throttle, you could feel the surge as the ALP shoved from behind - she had it up to about 86mph at one point, before beginning to slow for the next stop. Blended braking was smooth, too. Given the lower acquisition cost and lower maintenence costs of push-pulls, I think it's no contest.

keyboardkat wrote:I was on a Long-Branch-NY morning train the other day, which had six MLVs and an ALP46 pushing. The engineer had the front vestibule open, and I took advantage of it until a lady collector closed it. But when the engineer pegged the throttle, you could feel the surge as the ALP shoved from behind - she had it up to about 86mph at one point, before beginning to slow for the next stop. Blended braking was smooth, too. Given the lower acquisition cost and lower maintenence costs of push-pulls, I think it's no contest.

Would love to know from an engineer's perspective how they handle as more cars are tacked on. Then compare the less-than-flat NEC vs the coast line...