One more remark that was cut for time from this week's piece about Metro-North's recently-released RFEI for new bi-level cars is about the advantages and disadvantages of bi-level vs. single-level cars. Traditionally, single-level cars have been the default car type in the northeastern US (and much of the world), and bi-levels have only been introduced over the last few decades in a handful of places.
The principle advantage of bi-levels is you get more seats out of the same number of cars. A LIRR C-3 car sits between 137 and 143 passengers, compared to the single-level EMU fleet which seats an average of 106 per car, so over the course of a full 12-car train, you would be able to fit about 400 more passengers, which is nothing to sneeze at.
But bi-levels bring a number of big disadvantages:
Weight and acceleration
One of the most significant disadvantages of bi-level cars is weight. All those extra seats and all the extra equipment for those passengers adds significantly to the weight of the train. Once you add heavy and clunky locomotives (for push-pull trains) the train gets heavier. If you compare the weight per passenger car of bi-level push pull trains to other single-level trains in North America and modern EMU's/DMU's, you'll see that bi-level trains weigh significantly more than other types of trains.
The LIRR and NJT's bi-level trains weigh about 38% more per carlength than single-level push pull trains, which are comparable with the MTA's pre-modern EMU fleets (the M-7 and M-8 cars). These figures account for the weight of the car itself, plus the locomotive averaged out over the length of the train. LIRR and NJT bi-level push-pull trains weigh more than double modern EMU and DMU car designs found in Europe (and don't provide anywhere close to double the seats):
 |
| (blue bars = North American trains, green bars = European trains) |
Locks into push-pull
In the northeastern US, using bi-level cars also pretty much locks you into running push-pull trains, which brings with it a whole host of additional downsides. Not only do you have to buy the cars, but now you must also buy separate locomotives to haul them around. And acceleration gets even worse with locomotives over MU's, since that tractive power is being concentrated at only four axles, instead of distributed over the course of 24, 28, or 32 axles along the entire length of the train.
Distributing power along the length of the train is more efficient both space-wise and energy-wise. Some evaluations have pegged the energy efficiency advantage of MU's at 5% to 10% over that of locomotive-hauled trains, which can add up to a lot of savings in fuel and power costs over the life of the equipment.
NJTransit is purchasing a fleet of Multilevel III EMU cars from Bombardier to replace its old 1970's Arrow III EMU's, but those cars are still in the design phase so we have no idea if such a concept would actually work or how the performance would compare to typical EMU's. And even in the early concept stage, these cars are losing seats—a 12-car set of MLV III's is expected to have an average of 129 seats per car: that is 23 more seats than a single-level M-7 EMU (a 21% increase) but 21 fewer seats than a LIRR C-3 car. Though the big hitch is the cost: at $5.92 million per car, this fleet is extreemly expensive, well above and beyond the already budget-busting numbers we see in the US (for comparison purposes, the very expensive LIRR M-9 cars are costing $3.63 million per car, an off-the-shelf EMU from Europe costs about $2 million per car).
It is possible to do bi-level EMU's and still be within the small profile to fit inside the legacy tunnels in the northeast, but it gets very complicated and very expensive. On a typical high-floor, single-level EMU, all of the equipment for the cars is located in the undercarriage, below the passenger compartment floor. But on bi-level cars, that space is being taken up by additional passenger seats, so all of that equipment has to be relocated someplace else. Doing that either requires taking away passenger seats in another part of the car, or redesigning everything to squeeze stuff into nooks and crannies elsewhere in the car. You also often have to cheat on the dimensions and power demands of the components as much as possible to maximize the number of seats, which means that you lose out on performance, quality/reliability, or both.
 |
| NJT's MLV III will be record-breaking in good and bad ways (Photo: Bombardier) |
The added costs pretty much completely negate the benefits of going bi-level. When you break the math down to cost per seat, an off-the-shelf European EMU car will cost about $18,000 per seat and the M-9's are costing about $33,000 per seat. NJTransit's MLV III order will cost $45,780 per seat—37% more per seat compared to the M-9's and 150% more per seat than an off-the-shelf European EMU. If you go single level, you can often get even more seats for the same amount of money.
Dwell times and passenger flow
Another major disadvantage to using bi-levels is the impact to dwell times (the amount of time a train is stopped at a station waiting for passengers to board or alight). When it comes to managing dwell time, good passenger flow through the cars is important...you need a large number people to be able to move into and out of the cars quickly. Unfortunately bi-levels do not do anything to help that.
The staircases positioned right next to the doors introduces a chokepoint: the staircases are narrow that typically only one person can use them at a time, meaning you can't have passengers boarding and alighting simultaneously. Passengers also have to form a single-file line to go down the stairs to get off, and then boarding passengers must form a single-file line to go up the stairs to find seats. There is extra time added if people pause at the landing to peek upstairs and downstairs to see where there are more seats (as many people often do).
NJTransit's MLV design makes this even worse...by only including narrow one-person wide doors, they are guaranteeing that passenger flow is reduced to a single-file line to board, and then a single-file line to alight.
Couple the protracted dwell times with additional time lost due to slower acceleration and braking performance and you are looking at several minutes in additional running time over the course of a trip (more on a local train). If a railroad then uses bi-levels interchangeably with single-level trains, then all schedules must get extra padding so a train is not late just because it used bi-level equipment that day. That consequently impacts everyone.
When are bi-levels acceptable?
Bi-levels are an acceptable alternative to single-level cars for high-volume commuter/regional services when two conditions are met:
- The additional seating cannot be provided by extending the train with additional single-level cars
- There is no capacity to add additional new trains on the line
With the first test, if the actual length of the train is a real constraint, then it may be reasonable to expand upwards with bi-level cars instead of lengthwise with additional single-level cars. But these need to be real space constraints, like the configuration of the switches around your central terminal in a tunnel precludes longer trains because they would foul the switches—not that a railroad wants to be penny-wise and pound-foolish and only build tiny 4-car long platforms. Concrete is cheap and the additional dwell time benefits that come with full length platforms make it worthwhile. Yard layouts are also not really a legitimate excuse—most yards and sidings could be extended without much trouble, and trains should be out and about running more off-peak and reverse-peak service instead of sitting around in yards doing nothing.
In Metro-North's case, they fail this first test. It is rare to see a EMU train longer than 8 cars on the Hudson and Harlem Lines, and even on the New Haven Line 12-car trains are rare. All of MNR's push-pull trains max out 7 cars, or on rare occasions 8 cars. NY-Grand Central is not a constraint here. Most platforms are at least 10 cars long, and many are 13 or 14 cars long, even on the lower level. Outlying yards are similarly not that tightly constrained. Metro-North seems to at least have no real physical constraints that would bar all 12-car trains if they wanted to increase capacity.
On the LIRR, there are multiple different elements that make 12-car trains a reasonable upper limit. But there are still plenty of trains running around with fewer than 12 cars—only about 25% of LIRR trains are scheduled to operate with 12 cars (or 10 C-3 + 2 DM), meaning there is plenty of room to make trains longer in most situations.
The second test is about capacity... If you're trying to provide a certain number of seats on a particular line, having two 6-car trains is definitely better than one 12-car train if capacity constraints don't prohibit it. You are providing the same number of seats to that destination, but additional trains people now have more options to get where they want to go. But if you have maxed out the length of your trains and adding additional trains earlier or later isn't possible, then going to bi-levels to cram more seats into the same footprint may be worth considering. Though railroads have to make sure that the added running time implications that come with bi-levels don't actually reduce capacity due to slower running times and the need for additional dwell time and schedule padding.
The LIRR fails this second test, especially on the diesel branches. I don't think the LIRR is truly at capacity anywhere. Unlike Metro-North, the LIRR has three terminals (two of which are operated significantly under capacity) and both railroads can improve capacity by cutting down on schedule padding and standardizing schedule patterns.
Not a good fit for regional rail
All of the drawbacks of bi-levels make them not a good fit overall for high-volume regional rail services. When you are out west and size isn't a constraint and volume is much lower, bi-levels can be ok, but there's a reason they are not used much elsewhere in the world. Most modern regional rail services stick to single-level cars, and the few cases where bi-levels are used there are usually special circumstances that demand it and it ends up being clumsy and messy anyways.
Bi-levels should be a last resort when the system is genuinely constrained to the point where making trains longer or adding more trains is really impossible. For both the LIRR and Metro-North, I don't think they are close to that point yet...so sticking with single-level trains is the way to go for now.
No comments:
Post a Comment