Express Train Question

I ride a commuter train from the town where I live to the town where I work (and vice versa) a couple of times a week. It’s a two track system with one track reserved for northbound traffic and one for southbound (hopefully). There are 7 stops between where I get on and where I get off so it takes about 40 minutes each way.

In addition to the “milk run” as we affectionately call it, there are also express trains that run from one end of the system to the other without stopping at any stops. As I sit at the station waiting for my train I notice them whiz by and, of course, not stopping at my station.

My question is this. How can they run express trains when they are also running “milk run” trains. Wouldn’t the express trains get backed up behind a train that has to stop at every station? I’ve never seen a way for a train to pass another train (remember there are only two tracks) and I have never been passed by an express train during all of my years commuting. So what’s the deal?

They usually have extra tracks at the station for passing. The actual speed of the trains is the same; that is controlled by track conditions. Express trains don’t go faster, they just don’t have as many stops.

Assuming they do have extra tracks at the stations (I need to check on that) it still would require a fair amount of coordination since the Express Train would have to hit the station about the same time as any given milk run train… but I guess they must of figured that out.

A quick look at the Metra schedules for Chicago tells the story if there aren’t extra tracks for express trains to fly past local trains. Each express train basically cathches up to the train that left before it. If a train leaves every 20 minutes on the same route then the next train can skip stations till it catches up to the ‘slower’ local train. Usually at this point the express stops being an express and becomes local for the rest of its trip. In a few instances where it goes express again the train ahead of it ends its scheduled run halfway down the line, turns around and heads back (on the opposite track).

http://www.metrarail.com

Assuming they do have extra tracks at the stations (I need to check on that) it still would require a fair amount of coordination since the Express Train would have to hit the station about the same time as any given milk run train… but I guess they must of figured that out.

Yes, they would need to figure that out. That’s why they have schedules. If the trains travel on schedule, then they know when the local will be in the station and they know when the express will pass that station and each station in succession.

Also, the monitoring station probably has some control over travel speed of the trains if there are problems - radio to driver of express train (or control directly from station, whichever) that they need to slow up for some difficulty delaying station such and such. Then return to speed after that station.

“It’s a two track system with one track reserved for northbound traffic and one for southbound (hopefully).”

Actually, the answer to your question is that this (one track for north and one for south) isn’t always so! On many lines, especially where there AREN’T extra tracks or lots of sidings for passing, one or both tracks are bidirectional. Even on three-track lines, the center track is often bidirectional, as on the aforementioned three-track Metra lines.

This is not as dangerous as it may first sound. Most rail lines operate on a system of blocks – a block is simply the space between two signals – in which only one train may occupy a block at a given time. While a train is in a block, any train in the block behind is getting a red light telling it not to enter the block. On a bidirectional track, there are lights at BOTH ends of the block telling trains in both directions whether or not the block is occupied. Obviously, the beginning and end of a block have to be located properly with regards to the switches that allow trains to enter and leave that track from the other track(s). And scheduling is still as important as others have said, to ensure that there aren’t trains on both tracks keeping the express from passing. But where the signals and switches are laid out to accommodate bidirectional running, express trains CAN pass locals on a two-track line.

here on the LIRR - we get that all the time. 2 ways for this to happen.
1 the express leaves right ahead of the local and catches the local ahead of it.
2 use the other track as a passing lane

Also as mentioned above, extra track sections help out too

OK, looking at your profile, you live in Redwood City, CA.

Here’s the full CalTrain schedule. http://www.transitinfo.org/Sched/CT/_/A/

I’ll look at the vicinity of Redwood City here:


PA      Menlo   Athertn Redwood SCarlos Belmont Hillsd  HaywrdP SMateo
______________________________________________________________________
6:19a   6:22a   6:25a   6:31a   6:35a   6:38a   6:41a   6:43a   --
6:33a   6:36a   --      --      --      6:48a   --      --      6:54a
6:41a   6:44a   6:47a   6:54a   6:58a   7:01a   7:04a   7:07a   7:10a
6:59a   7:02a   7:05a   --      7:13a   7:16a   7:19a   --      --
7:08a   --      --      7:16a   --      --      --      7:26a   7:29a
7:22a   7:25a   --      --      --      --      7:38a   --      --
7:29a   7:32a   7:35a   7:42a   7:46a   7:49a   7:52a   7:55a   7:58a
7:46a   7:49a   --      7:56a   8:00a   --      8:05a   --      8:09a
7:54a   7:57a   --      8:04a   8:08a   8:11a   8:14a   8:17a   --
8:01a   8:04a   8:07a   8:14a   8:18a   8:21a   8:24a   8:27a   8:29a
8:28a   8:31a   --      --      --      --      --      --      8:44a
8:44a   8:47a   8:50a   8:57a   9:01a   9:04a   9:07a   9:10a   9:12a

SMateo  HaywrdP Hillsd  Belmont SCarlos Redwood Athertn Menlo   PA
______________________________________________________________________
--      --      5:19p   --      5:24p   5:29p   --      5:34p   5:37p
5:29p   5:32p   5:35p   5:38p   5:41p   --      5:48p   5:51p   5:54p
--      --      --      --      --      --      --      --      6:01p
--      5:50p   5:53p   5:56p   --      6:03p   6:07p   6:10p   6:13p

That doesn’t explain the one that skips everything before PA, though, so we need to look at that one:


SF     \ Redwood \ PA
_______/_________/_______
4:55p  \ --      \ 5:54p
5:20p  / --      / 6:01p
5:26p  \ 6:03p   \ 6:13p

So, from the looks of it, the express trains never actually catch up to or overtake the “milk run” trains.