B Line Lake St Rapid Bus, Midtown Rail Transit

[talindsay]

I hope to see as little single tracked as possible. Single track dedicated ROW is still preferable to shared ROW (Nicollet streetcar stuck behind a Toyota Matrix, ahem) but in this corridor there's plenty of room for two tracks, a wide trail, and plenty of greenery.

Agreed. It is, after all, a transit corridor.

[twincitizen]

When the time comes, a group of transit supporters might need to push back against the MBC here, at least on the west end single-trackage. As a cyclist, I loathe the idea of fighting with other cyclists, but unfortunately many of the Bike Coalition folks are the year-round riding, die-hard "bikes only" mindset that don't care much about transit.

Unfortunately, on the eastern terminus, there's probably nothing we can do about single trackage on the approach to the Midtown Blue Line station. Any future extension on that end would be considerably more expensive, and in the near term will be served by enhanced bus.

My concern is with the west end of the Midtown line. Distant future interling or future N-S tunnels aside, it may be warranted in the near-term to have higher frequencies on the denser western portion of the line (say 35W to West Lake) to make rapid connections with SWLRT. Alternatively, maybe the Midtown line could even be extended one or two stations beyond West Lake to create stronger connections between St. Louis Park and South Minneapolis, eliminating a forced transfer at West Lake Station. It is very important that the west end of the line be future-proof, and not be cemented (literally) as a terminal.

[MNdible]

Again, how much money do we really want to be spending to future-proof this thing for a future that's unlikely to ever come?

We have the option to build a very functional and affordable transit option, but we're going to puff up by building unnecessary double tracking. Resist the urge to let the perfection of your conceived future fantasy transit system get in the way of what's buildable and useful now.

[talindsay]

Again, how much money do we really want to be spending to future-proof this thing for a future that's unlikely to ever come?

We have the option to build a very functional and affordable transit option, but we're going to puff up by building unnecessary double tracking. Resist the urge to let the perfection of your conceived future fantasy transit system get in the way of what's buildable and useful now.

I'm a huge proponent of your general principle - build what's feasible now, not what fits into some unlikely future fantasy. For that reason I strongly dislike fantasy transit maps; I think it makes the most sense to focus on what's actually proposed and has good numbers from a current policy perspective.

That said, I don't think there's any reason to think that either a greater percentage of double-tracking or a link into the SW tracks at W Lake has anything to do with an "urge to let the perfection...get in the way of what's buildable now" - as decisions are made on this project they can choose to double-track in pretty much any percentage they like, and both 100% single-track and 100% double-track are very unlikely. It's already a grade-separated transit corridor, and the major cost issue, besides the additional steel and ballast, is retaining walls. Realistically I think very few bridges would be in the way of double-tracking, and the few that are in the way would be great places to evaluate whether the bridge needs replacement anyway or whether a short single-tracked segment is worthwhile. That's good decision-making, not urge of fantasy systems.

Regarding the tie-in at West Lake, the construction of Southwest is anything but fantasy as odds are that it will be built concurrently with this line. The tie-in of this line (as opposed to a terminal track) would only require the addition of one switch to the SW track (there will already be crossovers on SW anyway, and the W Lake station tail of this line will almost certainly be single-track); the presence of that single switch would so dramatically raise the flexibility of this line as contrasted to a standalone line, would reduce maintenance costs substantially and could likely remove the need for a separate maintenance facility, and so that switch seems a no-brainer to me but certainly isn't fantasy.

I don't think anybody has suggested this line needs to be 100% double-tracked with mandatory replacement of all old Greenway bridges, with a Central - Hiawatha - style double-track interchange with Southwest at West Lake; that would be the "perfectionist fantasy" scenario. Pushing for more double-track and a connection to SW is an argument for greater flexibility.

[Tcmetro]

Metro Transit has already shown it's feasible to build double track pretty much everywhere except the ends of the line. It provides maximum flexibility and doesn't require the reconstruction of bridges.

[MNdible]

I think that the last version of the proposal that we've seen looks like it's a very sane, functional, and buildable system with a reasonable mix of single and double track that will not impede operations.

As I recall, it has a connection to the SW LRT line for transferring vehicles in and out of service, and this makes a great deal of sense. Anything beyond that (for interlining regularly scheduled service) will just never be used. There is no forseeable future where they are actually going to run trains in service from Eden Prairie direct to the Lake Street Blue Line station.

IMHO.

[woofner]

The MBC post framed the issue poorly, and I hope that the MGC and the BAC didn't have the poor understanding of the trade-offs that was implied by the post. The difference between single-track and double-track is much less about travel time and more about frequency and reliability. To be fair, I'm not sure that the project office has done much to quantify these issues. From what I can tell, they claim that 10 minute frequencies will be possible under both options. The only single track urban rail line I'm aware of (Tampa doesn't count) is SLC's Sugar Hill line, which maxes out at 20 minute headways. I would want to know from the Met Council what the max headway capable under the single track option is, because I can see good chances for 7.5 minute headways becoming necessary after SWLRT opens, and dream about even higher demand. Also I'd want to see what kind of reliability modeling has been done (if any) and how the two options differ in that regard.

[Andrew_F]

Another thing to think about re:interlining and double track is the possibility of a future Nicollet/Central connection. I understand MNdible's argument regarding not spending too much money on trying to future-proof for things that aren't going to happen for certain yet, but I think even in the mid-term this corridor obviously experiencing rapid growth and this line has the potential to justify major frequency increases and connect to many other planned corridors. I think seeking as much double-tracking as possible is a pretty reasonable balance between not wasting resources on things that stand a good chance of requiring modification in the near future and not wasting resources on preparing for things that are unlikely to ever materialize.

[Nick]

Again, how much money do we really want to be spending to future-proof this thing for a future that's unlikely to ever come?

We have the option to build a very functional and affordable transit option, but we're going to puff up by building unnecessary double tracking. Resist the urge to let the perfection of your conceived future fantasy transit system get in the way of what's buildable and useful now.

I feel like pointing out that, in terms of whacky, pie-in-the-sky tactical strategic networking urban happy hour ideas, "N-S subway in South Minneapolis" in the next few decades is certainly a lot more plausible than, you know, elevated rail to Rosedale operated by community groups, or whatever.

[MNdible]

Sure, but what do we really need to do now to the Midtown Corridor to prepare it for this possibility that we couldn't just as easily do later, when we're spending billions of dollars on our new freakin' awesome subway?

[RailBaronYarr]

That's a very good question. I don't know the answer, but it seems like if there are slight to moderate operational benefits in the now for double tracking as much as possible in the hopes that it reduces the future cost of doing that exact same thing, it would seem worth it. I think woofner's questions about some detailed modeling on reliability based on multiple single/double track scenarios are completely valid, and the type of rigor we should expect from these projects.

[David Greene]

Also I'd want to see what kind of reliability modeling has been done (if any) and how the two options differ in that regard.

Agree 100%. But just so I'm clear, by "reliability" do you mean on-time performance?

I will definitely ask these questions at the next CAC meeting.

[RailBaronYarr]

Also I'd want to see what kind of reliability modeling has been done (if any) and how the two options differ in that regard.

Agree 100%. But just so I'm clear, by "reliability" do you mean on-time performance?

I will definitely ask these questions at the next CAC meeting.

I'm no transit modeler, but I would imagine a good output would be some 4 dimension set of data that shows on time rate (%) for a given headway for each station for a given dwell time (like if the train has to wait 10, 20, etc seconds longer than expected at a stop how does that affect performance down the line). Lots of charts or tables to understand the impact. Understanding what frequencies at what levels of ridership (people congestion) gives the ability to know the usefulness of the line into the future and how much the investment risk is worth.

[mulad]

It should be possible for someone to produce some string-line diagrams for service on the line -- a plot of the position (y dimension) versus time (x dimension) for each of the vehicles running on the route -- or perhaps a tool to allow people to make their own. Here's a complicated example from a site discussing the integration of high-speed rail and Caltrain commuter service in California: http://caltrain-hsr.blogspot.com/2011/0 ... eeded.html

Fortunately, the modeling for Midtown would be simpler, since all of the vehicles should be the same, hit all of the same stops, etc. It's important to find where the lines cross each other -- any of those points (as well as some space ahead and behind) should have sidings/double-track in order to allow trains to pass.

There's a back-and-forth between running the model to get a first guess at where sidings/double-track may be needed, and then tweaking the schedules to fit what's possible/reasonable.

It's also a good idea to model what happens if a segment of track goes out of operation -- the Hiawatha LRT sometimes goes down to single-track operation over a segment when there's a car-train collision, for instance. But sometimes the incident causes enough of a mess that even single-track operation isn't possible.

So, it would be nice to have some measure of the reliability of the service due to normal delays with passenger boarding, etc. -- and the ability to recover from delays -- plus some attempt to quantify the line's resiliency/robustness/tolerance when bigger problems occur.

In other words, it would be possible to build a streetcar line that's mostly single-tracked and only have short passing sidings where the string-line diagram says that streetcars would pass if they're running on schedule. In practice, it's better to have longer sidings than the minimum necessary, and more of them in order to handle cases where vehicles are delayed and end up passing at a different point on the line.

It's also important to note that switches and signals are expensive -- in many cases, it is better to have longer segments of double-track rather than a number of shorter sidings that have expensive hardware at each end.

[mattaudio]

Have they considered gauntlet track rather than single track? Signaling would be required to prevent intrusion, but it would be much less complicated than switching.

[bubzki2]

Yeah, gauntlet track would seem the obvious choice considering the nature of this line. Not sure I've heard it mentioned though.

[talindsay]

The original MGC proposal utilized gauntlet track extensively. It's on their radar, but I don't think Metro Transit would be a proponent since it gives all the potential hazards of switches to single track, without the flexibility.

Another thought that just occurred: how would they handle bus operations to replace the service when it's disrupted for some reason? Would they just make everybody go to Lake, I assume?

[LRV Op Dude]

Have they considered gauntlet track rather than single track? Signaling would be required to prevent intrusion, but it would be much less complicated than switching.

Here is a great example of light rail systems using interlaced (gauntlet) and bi-directional single track.

[FISHMANPET]

Gauntlet tracks are probably cheaper than switches, and they don't require anything to actually be switched. You still need the signalling as if it was single track, but you don't need the actual switches.

[talindsay]

Gauntlet tracks are probably cheaper than switches, and they don't require anything to actually be switched. You still need the signalling as if it was single track, but you don't need the actual switches.

Right, typically it's cheaper since there are no switches. The operational issue is that single-track sections essentially function as basic crossovers, which lends some operational efficiency that's lost with gauntlet track.