Thursday, May 10, 2012

Why commuter railroads won't run diesels

Earlier I talked about why freight will never electrify their railroads. Now I'd like to show, by way of an example, why commuter railroads won't run diesels in the future, choosing instead to electrify their lines. There are a couple of reasons for this.

Firstly, operational costs have a far greater prominence than do capital costs owing to the nature of government agencies as opposed to private agencies. An investment that is hard to justify for a freight operator becomes much easier for a public agency that is receiving "free" funding from another agency and in the process is able to reduce its operational costs to those to whom it is immediately responsible. In such a way does spending hundreds of millions of dollars to save a few million per year become an attractive financial option.

More importantly, however, is the fact that electric trains accelerate much faster, and electric multiple units, compared to a diesel locomotive hauling several rail cars, accelerate like a bat out of hell. The Fairmount DMU study gives the acceleration characteristics of a diesel push-pull train set such as MBTA and other commuter agencies use. Accelerating to 60 miles per hour takes 166 seconds; by extrapolation of the acceleration trend, 80 miles per hour would take 301 seconds. That's significantly slower than the Talent DMU that my last post featured, but look at it in comparison with a Stadler FLIRT:

The FLIRT reaches 60 miles per hour in only 27 seconds, over two minutes faster than a traditional American train set and reaches 100 mile per hour in about 76 seconds, a minute and a half before our vaunted American train has hit 60 miles per hour (it's just about to hit 35 miles per hour). It also breaks significantly faster.
In this video we can see a deceleration from 70 kilometers per hour to 10 kilometers per hour in 9 seconds, which is an average braking rate of 6.67km/h/s or 4.145mphps. This NTSB report on a Metrolink train exceeding a stop signal reports:
The third test used the service air brake and dynamic braking but did not use the emergency brake. The brakes were first applied when the train reached 74 mph. In this test, the brakes were applied in increments, as in the first test; however, there was less time between brake applications. The total stopping distance was about 2,490 feet.
Working backwards from the stopping distance equation on page 21 of a Department of Defense study on using TGVs to haul M1 Abrams tanks, the train's stopping rate is only 1.62mphps, about 40% that of the FLIRT.

The upshot of this is that more time is spent at higher speeds, reducing the time penalty for any individual train stop and greatly increasing the average speed, making it more attractive to travelers and increasing its patronage, and political support, as a result. By way of example, I ran a calculation of trip times using the Stadler FLIRT, as demonstrated in the above videos, to see how this would affect Metrolink's schedule between Laguna Niguel, the most southern point on the OC Line where NIMBYs and single tracking are not a concern, and Los Angeles Union Station. For this purpose, the use of Metrolink and BNSF timetables was invaluable. I assumed a 30 second dwell time, that unless it resulted in only ~.1-.2 miles of cruising acceleration to and braking from the maximum legal speed were called for and that all curves were accounted for by the speed limits. Additionally, while it is not always true, it was assumed that the mileposts were accurate and that they did equal a true mile. Briefly following is all the speed limits, to save others the trouble.

Laguna Niguel-Irvine: 8.7 miles (MP 193.7-185) 90mph all miles
Irvine-Tustin: 5.5 miles (MP 185-179.5) 90mph all miles
Tustin-Santa Ana: 4.3 miles (MP 179.5-175.2) 90mph till 176.1, 50mph after
Santa Ana-Orange: 2.6 miles (MP 175.2-172.6) 50-174.7, 79-173.8, 40-173.2 60 after.
Orange-Anaheim: 2 miles (MP 172.6-170.6) 60-172.4, 35-172, 79 after
Anaheim-Fullerton Jct: 4.4 miles (MP 170.6-165.4) 79-170.4, 70-169.2, 79-165.9, 55-165.4
Fullerton Jct-Fullerton: .4 miles (MP 165.4-165) 79mph
Fullerton-Buena Park: 4.7 miles (MP 165-160.3) 79-163.8, 75-163.5, 79-161.1, 70-160.8, 79 after
Buena Park-Norwalk: 4.2 miles (MP 160.3-156.1) 79-156.6, 75 after
Norwalk-Commerce: 7.6 miles (MP 156.1-148.5) 75-155.9, 79-154.2, 70-153.8, 79-153, 50@153, 70-152.5, 79-152.1, 50@152.1, 79-151.7, 65-151.4, 79 after
Commerce-Soto: 4.1 miles (148.5-144.4) 79-144.5, 40 after
Soto-LAUS: 4.2 miles to CP San Diego JCT (144.4-140.2), 0.2-CP Mission (MP 0.8), .8 to LAUS (MP 0.0).
144.4-142.8 44mph, 142.8-141.2 79mph, 141.2-140.8 45mph, 140.8-140.2 35mph, 0.8-0.5 25mph
The current schedule reads as follows, adjusting to make a Laguna Niguel departure :00 (using train 603)
0:00 Depart Laguna Niguel
0:09 Irvine
0:16 Tustin
0:23 Santa Ana
0:28 Orange
0:32 Anaheim
0:41 Fullerton
0:47 Buena Park
0:55 Norwalk
1:05 Commerce
1:19 Arrive Los Angeles (there are 7 minutes of padding which makes scheduled time 1:26)

Calculated with a FLIRT:
Laguna Niguel-Irvine
Leaves 0:00:00 arrives 0:06:18 departs 0:06:48
Leaves 0:06:48 arrives 0:10:58 departs 0:11:28
Tustin-Santa Ana
Leaves 0:11:28 arrives 0:15:20 departs 0:15:50
Santa Ana-Orange 
Leaves 0:15:50 arrives 0:18:52 departs 0:19:22
Leaves 0:19:22 arrives 0:21:42 departs 0:22:12
Leaves 0:22:12 arrives 0:27:16 departs 0:27:46
Fullerton-Buena Park
Leaves 0:27:46 arrives 0:31:46 departs 0:32:16
Buena Park-Norwalk:
Leaves 0:32:16 arrives 0:35:52 departs 0:36:22
Leaves 0:36:22 arrives 0:42:29 departs 0:42:59
Commerce-Los Angeles:
Leaves 0:42:59 arrives 0:53:25

Obviously in practice and as put on a schedule, the gains would not be as great, but it does indicate gains of up to 26 minutes from Laguna Niguel to Los Angeles Union Station are possible. This is, in many respects, a best-case scenario. The FLIRT is among the best accelerating train sets, it would require a waiver to operate in the United States, and it has limited seating rendering it somewhat less suitable for commuter operations (a six car unit has 260 seats and while American commuter seating density would raise it to about 425-450, a comparable bilevel six car set offers nearly double the number of seats). While multiple-units can alleviate this, it would require greater staffing, Metrolink's contract, which is similar to Amtrak's, requires an additional conductor if there are more than six cars. 

I'll also admit that I can't shake the feeling I messed up the partial braking calculations, although it shouldn't greatly affect matters; at most I suspect it would counteract always rounding up acceleration and braking distances to the next tenth of a mile.

That, in a nutshell, is the advantage which electrification offers alongside fuel savings: a 33% reduction in travel time and making commuter rail operations truly time competitive with car travel. In this particular instance, the cost would be about $500 million or less for the electrification, plus the cost of train sets (Hungary recently purchased four FLIRTs for 20 million euros), and much of the electrification cost can be covered through the California High Speed Rail program, making the burden more manageable on OCTA and the other Metrolink member agencies. 


  1. Yes! Now just get the MBTA to agree.


    1. The MBTA's behavior is perplexing to say the least. They (or the state) now own all the lines they run on, and the part Amtrak runs on is *already* electrified. They have a great deal to gain by electrification.


  2. I think doing this analysis for the San Benardino Line would be interesting.

  3. Really insightful analysis. Electrification would also reduce dependence on heavily imported liquid fuel. Air pollution would at least be relocated from urban areas where trains opperate to more remote locations where electricity is generated, and may even be reduced somewhat overall depending on the nature of electrical production.

    Additionally there are a few track segments you note that have very low speeds. It may well be that the cost/benefit return doesn't justify improvement of these segments for diesel trains, but electric trains might be able to take more advantage of such improvements thereby shifting the cost/benefit analysis.

  4. Spokker:
    San Bernardino
    Depart 0:00:00
    Arrive 0:06:29 Depart 0:06:59
    Arrive 0:10:17 Depart 0:10:47
    Rancho Cucamonga
    Arrive 0:16:26 Depart 0:16:56
    Arrive 0:21:08 Depart 0:21:38
    Arrive 0:24:01 Depart 0:24:31
    Arrive 0:25:46 Depart 0:26:16
    Arrive 0:28:02 Depart 0:28:32
    Arrive 0:35:35 Depart 0:36:05
    Baldwin Park
    Arrive 0:40:29 Depart 0:40:59
    El Monte
    Arrive 0:47:12 Depart 0:47:42
    Cal State LA
    Arrive 0:55:50 Depart 0:56:20
    Los Angeles Union Station
    Arrive 1:05:19

  5. The two main differences between commuter and freight rail are not who owns it. Private commuter railroads were often electrified from the start - e.g. interurbans in the US, private railroads in Japan. Rather, the distances on commuter rail are shorter, so the capital cost of electrification is reduced; and commuter trains need to make frequent stops, so diesel trains are less fuel-efficient and lower-performance.

  6. Those were all built back in the steam era however, and steam had absolutely horrendous low speed acceleration and higher crew and other operating costs. By the time that diesel locomotives first made their appearance in the mid 1920s and came into their own in the 1930s, interurbans in the US were well on the decline. I'll admit I don't know the history of Japanese railways, but a brief overview suggests that there is a similar timing consideration.

  7. »(a six car unit has 260 seats and while American commuter seating density would raise it to about 425-450, a comparable bilevel six car set offers nearly double the number of seats).«

    A certain four car double deck EMU offers 335 seats, with 30% more kW/t than the Flirt (which should have even better acceleration): Stadler KISS for S-Bahn Bern (PDF, german; no englisch available)

    1. Source page for the above link :
      "KISS | Vehicles"
      It looks like they were intending to do versions in English and Polish.

  8. Sorry, not inNJ. Most NJ Transit lines are dieselized and will never be electified.

    1. They may be dieselized at present, however electrification is increasingly likely as time passes.

    2. The CNS&M "North Shore" standard cars had an acceleration of 2 mph/sec in the 1930s-1960s.

  9. At some point would hybrid/electric not give you the best of both worlds? Electric acceleration w/o the fixed infrastructure.


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