Tag Archives: speed

Improving transit speed part 1

Over at Portland Transport, EngineerScotty (also author of the Dead Horse Times) posted on improving transit speed downtown, particularly for MAX. It’s an interesting post and a lot of different ideas have come up in the comments. I was going to respond there but it got long, so I’m taking it here and breaking up my thoughts on the different suggestions that have been made.

The first of these…

Train Length

One of the constraints of MAX brought up in the post is train length – Portland city blocks are about 200 feet, and a two-car consist is about 184 feet (191 feet if it’s a Type 4). All lines run through downtown, so the system is designed around that 200′ maximum length for trains. Early on in the thread, one commenter asked why we couldn’t run a train that’s twice as long (a four-car consist rather than the two-car consists run now) – even if it blocked a street while it serviced a stop, it wouldn’t be there long and this would double the capacity of service.

Dead Car PushThe exception, not the rule

Mechanically speaking and not taking anything like platforms into consideration, the cars are capable of being coupled together in consists longer than a two-car train. I haven’t really posted about how cars are coupled aside from answering questions in comments, but the trains are coupled in two ways: a mechanical couple and an electrical couple. The mechanical couple is what physically holds the cars together; the electrical couple is what lets the cars talk to each other. For example, this allows the operator to hit the door open button and have all the doors in the train open, not just the doors in the car that the operator is sitting in (this is called “trainlined” and yes, that’s where the safety communication gets its name). That works if there are two cars coupled together, or three, or four. I don’t remember if more than four cars can be electronically trainlined. This does not work for Type 4s. The coupler head located under the cabs of those is there to be used for a dead car tow or push and is capable of being mechanically coupled to any car in the fleet, but there will be no electrical communication between them.

Screen shot of Bob R’s video of the A-cab coupler head

So aside from the 4s, more than two cars could be coupled together and still function. However, there are a number of reasons why it would take so much money in construction costs to run 3-car or 4-car consists to the point where it’s just not worth it.

For one, the previously-mentioned trainline opens all the doors of the train. Assuming you have a four car consist downtown, if the operator stops to service a platform (we’ll use Pioneer Square North as an example), the rear two cars are going to be blocking SW 6th and going back up the block between 5th and 6th. When that operator opens the doors, all of the doors in the train are going to open, and remember that even on the low-floor cars, there’s a drop to the ground below when not at a platform:

Climbing into a Type 2 from the ground

So that would be opening the train doors onto the street, and even for people not using mobility devices, that’s not a comfortable way to get on or off the train. And to lengthen all of the platforms in the system to accommodate longer trains would be prohibitively expensive (just the Washington Park stop alone would be a logistical and financial nightmare)

There’s also the matter of what to do when the train gets to the end of the line.

In the Jackson turnaround

Here at Jackson St, which is currently the end of the line for Yellow and Green trains, the first and third tracks are big enough to accommodate a two-car train, but nothing larger. The circuits in the turnaround are only big enough for one two-car train. I took this picture from the leading car looking back toward the trailing car, and the last wheel axle of the trailing car is just past the insulated joint on the eastern entrance to the turnaround. And the center track can only accommodate a single car train, such as the mall shuttle. In short (pun not really intended), there’s no room for a train longer than two cars here.

So that means no four-car consists on the Yellow-Greens, which is good because that would make things much more difficult for buses driving on the transit mall. What about on the Blue line? Cleveland has a tail track, so there actually is room at the east end of the line in Gresham. Heading out to the west side though, there’s a lack of space. Here’s a view of the platforms at Hatfield Gov Center, the western terminus of the Blue line:

Western end of the Blue Line

As Hatfield is now, there’s no room for a train longer than two cars – to lengthen the platforms would mean shutting down Main Street which runs behind the building there.

It’s not just a lack of space and platforms big enough to accommodate them that that make it impractical to run longer consists.

Paradoxically, longer trains would actually mean slower running speeds in many sections of the alignments. At Goose Hollow (above), for example, the speed limit around that curve for eastbound trains is 10mph, and a train can’t accelerate until the entire consist is clear of the curve. You get thrown around quite a bit if you’re near the back of a trailing car going around a curve and the operator accelerates before you’re out of the curve.  If the trains were twice as long as they are now, that’s waiting until another 200′ of train has gotten through a curve before the train can accelerate.

In other places, gravity would work against longer trains. For example, heading into the tunnel westbound, the speed limit is 55mph past the first cross passage. As things are now, if your train is a two car consist with a crush load of people, it’s hard to get to 55mph since you’re climbing a hill with all that weight. If you’ve got twice as many cars and people, it’ll run even slower. Longer trains might mean more capacity, but ultimately they’d mean slower running speeds.

So it’s an interesting idea to run longer trains, but it would involve so much construction to existing platforms, major modifications to city blocks in the CBD, to say nothing of the work involved in changing the circuits in the rails to accommodate longer trains that it’s not feasible to do.

More to come.

Restricted Speed

And for today, a definition.

Restricted speed for a MAX train is:

20 miles per hour or the posted speed (whichever is less)

but always at a speed that would allow the operator to stop within half their sight distance.

Thick fog at night limiting visibility

So for example, downtown where the speed limit is 15 mph, restricted speed would never be faster than 15, but in areas where the normal speed limit is faster, restricted speed will be a maximum of 20 mph. Conditions like thick fog that reduce how far the operator can see ahead will likewise reduce the maximum speed permitted under restricted speed.

Situations in which restricted speed would be used include -but are not limited to- any time a train is running reverse traffic (e.g. east in the westbound tracks) or after bypassing a red ABS signal, or as directed to by Control.

EDIT – I’m updating this post with clarifications after being contacted via email which made me realize I’d worded some of this unclearly. Under normal operating conditions, something like a foggy night could get a warning from Control that you should operate at a speed that you feel comfortable and safe going at, which does not mean restricted speed – if the speed limit through a foggy area is 55 but you feel safe at 40 or 50, that’s fine. It is only when Control has stated that you should operate at restricted speed that the 1/2 sight distance restriction comes into play.

How fast do the trains go?

Question: How fast do the trains go?

Rush hour on BanfieldFaster than the cars do during rush hour, at least.

Max (no pun intended) speed

The trains have a governor built in that brings the train to a smooth yet irretrievable stop if it goes above about 58mph (though some of the Type 1s are more like 60mph). This is called an overspeed and (thankfully) is not a rule violation since a lot of new operators overspeed by accident their first time going down a hill.

SpeedometerSpeedometer of one of the low-floors, I think this was a Type 3.  Sorry for the reflection of my safety vest!

The type 1s, 2s, and 3s have three “speed maintain” or SM modes to prevent overspeeding when going down a hill – SM 1 prevents a train from going faster than 55mph on a hill, SM 2 prevents a train from going faster than 35mph, and SM 3 tops off at 15 mph.  There aren’t overspeeds associated with the SM modes, they just sort of work like cruise control when going downhill that they’ll hold a train at that particular speed and prevent it from going over. The type 4s are a little different – those can be set to any speed and maintain it whether going up or down a hill, which is part of the reason the ride quality of the 4s is so smooth.

Speed Limits

Yes, the rail alignment has speed limits, and yes, speeding is a rule violation.  Speed limits on the mainline range from 5mph to 55mph.  From fastest to slowest, here are examples of the speed limits in assorted areas of the mainline:

55mph

Cars on I-84 during rush hour will be slower than you.55mph on the Banfield

Many stretches in ABS territory have a speed limit of 55mph, which can be done since ABS territory is dedicated rail so there isn’t a worry about running with vehicle traffic.  In areas where there are curves, gated intersections, platforms, etc, the speed limit will be lower.

35mph

Burnside speed limitI didn’t take this picture – borrowed from another rail operator’s blog

35mph is the maximum speed limit in pre-empt territory, found along most of Burnside. All of my Burnside pictures are too dark to be worth posting so I had to borrow this one.

30mph

Interstate Ave Speed LimitSame as above – didn’t take this picture, borrowed from a rail operator’s blog

30mph is the maximum speed limit along Interstate.  The Yellow Line doesn’t pick up any appreciable speed until the Vanport Bridge, which is the only area of the Yellow Line alignment that is ABS territory.

25mph

Holladay – eastbound from Oregon Convention Center to 7th & Holladay

Along Holladay in Portland and Washington St in Hillsboro (both pre-empt territory), the speed limit is 25mph.

20mph

Westbound out of the tunnel into Goose Hollow

Some of the hills have a speed limit of 20mph, like this part exiting the tunnel eastbound.  (Sorry about the bit in the video where it goes sideways!)

15mph

CBD at nightIn the CBD (both the original Blue & Red line east/west alignment as well as the north/south Portland Mall alignment) the speed limit is 15mph on the straight sections of track.  Around some of the curves in this part of the alignment (Goose Hollow, PGE Park, Skidmore Fountain, 1st Ave, and that area up by Union Station), the speed limit will be 8mph or 10mph.

10mph

Bridge spanRemember when cars used to drive across the middle section of the bridge?

The Steel Bridge span – not the entire bridge, just the part that can be raised.  Even at that low speed you can feel a pretty large bump going over the bridge joints – the speed limit isn’t that low to protect the structural integrity of the bridge, but rather the vibrations created by going faster can damage the microswitches on the machinery on the bridge.  Getting up to the span and once the entire train is off, the speed limit is 15mph, same as the rest of the CBD.

Train on bridgeTrain on the bridge span, taken from the waterfront

The “fishhook” – that curve after Gateway that is used to diverge to the airport alignment is also 10 mph.

5mph

Over some switches, the speed is 5mph – you’ll see this entering or exiting Hatfield in Hillsboro, and also heading west into Rose Quarter. When the Yellow Line used to turn around at 11th Ave, the speed over those switches was also 5mph, as are the switches into and out of the Jackson turnaround by PSU.

5mph west into Rose QuarterThe train I’m in at the eastbound platform at Rose Quarter is stopped, but that train with the type 1 lead car is only going 5mph because of the switches into the westbound platform

Platform speeds

The speed limit into platforms is 20mph or the posted speed, whichever is less.  The front of the train must be at that speed by the time it reaches the near end of the platform.  There are some platforms where the approach speed is slower (e.g. Rose Quarter westbound as previously mentioned because of the switches, Millikan Way westbound because of poor visibility, Gateway and Beaverton Transit Center because they’re so busy, etc) but most are 20mph.  An out-of-service train bypassing a platform will also slow to 20mph until it’s clear of the platform.