Greater Triangle Commuter Rail Project Update

[orulz]

Originally Posted by TrafficSys

(Clipped a little to shorten the message)

Thanks for the excellent explanation. I never thought too much about this before. Especially the weight of the diesel engine or the batteries affecting performance (knew more weight affected acceleration, of course, remembering my basic physics, but not in this application!)

Looking at pictures of HSR in Europe (I picked one from France) it looks like only the lead car has the wire sticking out to connect to the overhead wires. I presume the couplings between cars includes electrical connections, and each car has powered axles? (I probably missed a redundant power arm (not sure what to call it) somewhere else on the train.)

IIRC, each subway car has an arm(s) reaching out to the third rail for power, as opposed to just the front car.

The type of current collector almost always used on mainline and high speed rail is a pantograph.

The N700 Shinkansen train in this photo has two pantographs, but typically only one is raised. All axles are powered by the current collected through that single raised pantograph. You can get enough power through a single pantograph, because the voltage is so high (25,000 volts) that you don't need a lot of current in order to transmit a lot of power. As you have guessed, there are wires that distribute the power among all the axles on the train.



Having motors on *all* axles is not universal, however. Other trains might power half the axles. Others like the British Rail Class 800 have the axles on some cars powered, and on other cars unpowered - 5 car trains have 3 with powered axles and 2 without; 9 car trains have 5 with powered axles and 4 without. Some trainsets, like early TGVs, would only have motors on the first and last car. This is what Amtrak does, to this day. It's a tradeoff between design complexity/cost, weight, performance, interior space, and such.

The more frequently your train stops, the more that extra powered axles, and the extra power delivered by overhead wire helps. If you're running nonstop for a hundred miles, taking an extra minute to get up to speed doesn't matter a whole lot. If you're making twenty stops along the way, it sure does!

[n24scube]

Originally Posted by orulz

Making train passengers headed from Raleigh to Durham ride 3 miles up the RDU spur, and then 3.5 miles back down, would add at least 10 minutes to the trip time, probably more like 15. That would erase any speed advantage that rail has over a bus, and would a absolutely decimate ridership.

When you're designing a train line, always remember that everybody wants to get where they're going as quickly as possible, which means traveling in as straight of a line as possible. Adding a 6+ mile detour would decimate the potential ridership. Even worse, it's an out-and-back detour, meaning you wind up duplicating service on the route along Airport Blvd between the rail line and RDU - so you're not even providing useful service for part of the route. You probably don't intend it this way, but if you think about it, a service like this seems almost contemptful of riders' time. "You should be thankful that we're building you a rail line at all! Who cares if you have to wait 10 extra minutes to get where you're going. Shut up and be appreciative."

BART did something like this at the San Francisco airport, with their connections to Caltrain at Millbrae, and SFO. They have tried all manner of service plans, including ones where trains curve into the airport and back in to Millbrae; where trains go straight into Millbrae and then back into the airport; and where services from San Francisco dead-end at Millbrae and the airport, an Millbrae-Airport is run as a shuttle.

It works, and people are glad to have rail to the airport, but:

1. It's just a half-mile detour from the main line (not three miles!)
2. It's near the end of the line, not smack in the middle of it - people would think differently if this detour were at the midpoint between Oakland and San Francisco.
3. Even then, it's a hassle. If you're going to the airport, and your train has to go into Millbrae and then back out, or vice versa, it feels like a frustrating imposition to change directions like this. It inevitably takes a few minutes for the train to switch directions.

Now, your route might make sense some day - but only:

1. As a future phase, after Raleigh-Durham service is already up and running, and likely after the lines to Wake Forest and Apex are built as well.
2. Raleigh-Durham direct service continues to run
3. Raleigh-Durham direct service doesn't sacrifice frequency in the name of the RDU train)

Honestly, If I could really have my way, I'd prefer it as a separate line. An automated metro that starts out as a connector from an RTP rail station to RDU, but eventually gets extended all the way down Glenwood to Raleigh.

Future phase, though. Raleigh-Durham is the top priority.

I agree it'd be a negative for every train to run via RDU. not every train needs to. Could be every other or 2x an hour. To be honest I don't see rail ever happening in the Triangle for many of the reasons discussed here by others, but my point was only to say it is possible to run a spur and connect the airport *IF* (and that's a HUGE IF) rail ever actually happens here.

[wizard-xyzzy]

I voted for the transit tax although I'm retired and won't benefit from it. To be frank, I think the value of the commuter line to the Triangle to the commuting public will be negligible at the outset. However, it will encourage transit-oriented development right away, and it will prove to be significant 10 or 15 years in the future -- assuming the Triangle continues to grow in population. I-40, NC 54, NC 55, US 70, etc are as large as they'll ever get. The real question is what kind of a Triangle do you want to see in 2050. Of course, that question is somewhat polluted by political and land-owner interests in downtown Raleigh and downtown Durham who want to make sure that the downtowns remain a focus for development.

Questions about rail transit into RDU are repeatedly raised on this forum, and of course the (correct) answer is always the same.

I've ridden electric trains in 15 or so countries. All of them have a higher population density than the Triangle. Of course, 95% of railroad infrastructure in the U.S. is optimized for freight, not passenger. The freight RRs periodically study electrification but the economics just don't work. In fact, the freight RRs turned off the electrification that they did have.

The weight of the diesel engines in diesel-electric locomotives isn't much of a factor if you're pulling a 15,000-ton freight train. To avoid locomotive wheel slip, you need a certain amount of axle loading on the locomotives. If the weight doesn't come from the diesel engine and the accompanying fuel tank, it has to be something else. Passenger trains don't weigh nearly as much.