Wye Not? | streets.mn

Imagine arriving at the Mall of America light rail station and seeing trains for both downtown Minneapolis and downtown St. Paul, and not waiting 20 years until the Riverview Corridor is built.

When the Hiawatha Line (today’s Blue Line) opened in 2004, it had service every 7.5 minutes (8 trains per hour). [As of this writing, Wikipedia still thinks it does]. Today it has service every 10 minutes (6 trains per hour). In exchange service was transformed from to 3 car instead of 2 car trains. Most transit riders I know would prefer the more frequent service. (Most auto users of course prefer fewer trains, as that means less problems at traffic signals.)

Engineering sketch of Cedar-Riverside Wye Junction.

When the Central Corridor (today’s Green Line) was proposed, it was to have “16 trains per hour“, i.e. service every 7.5 minutes in each direction. Today it has service every 10 minutes. The bottleneck, we are told, is downtown Minneapolis, where the lines come together, providing train service every 5 minutes.

However most users of the Green and Blue Lines are not going downtown. Many are going to other destinations along the line. That is what keeps them in business. In fact, many riders transfer from the Green Line to the Blue Line (and vice versa) at Downtown East.

Suppose in addition to today’s service MetroTransit provided one more service, let’s call it the Cyan Line*, running from St. Paul to Bloomington, requiring very little additional construction, and no additional train cars (if we are willing to reduce the number of cars per train), that did not further congest the critical points in downtown Minneapolis.

MetroTransit could add about 3 trains per hour (one more train every 20 minutes) with no additional cars if each train went from 3 car to 2 car length, for a total of nine trains per hour (9*2 = 6*3). Alternatively, they could just buy more cars. (To achieve the “High-Frequency Network” designation, there would need to be 4 trains per hour in each direction, though since the lines already have service, I am not sure this is required).

To achieve this, MetroTransit would need to construct the small section illustrated in the figure (map). This Wye Junction would take very little land in Currie Park, and quite possibly no buildings. Some park land would need to be replaced. (I see some nearby surface parking that would be suitable, if not land bridges/interstate lids/freeway caps.)

What the Cyan Line service (shown in figure 2) achieves is not so much direct access from St. Paul to Bloomington, which would be a very long trip (on the order of an hour), but direct access for other Green Line origins (destinations) like the University of Minnesota to Blue Line destinations (origins) like South Minneapolis, the Airport, and the Mall of America.

Metro Transit Diagram with Cyan Line added

Shorter distance trips on the same line (e.g. from Lake Street to the VA, from Snelling Avenue to downtown St. Paul) would also see increased service. Once eastbound on the Green Line at West Bank, it changes from Cyan to Green Line designation since they share a common destination. Once southbound on the Blue Line it changes from Cyan to Blue Line designation .**

As we know, transit is a positive feedback system. Cut back the service, and ridership drops. Lose more riders, cut more service. This works in both directions. Add service, ridership increases. Ridership increases justify more service. Over the long run, land use patterns change.

How much will this cost? I don’t know, but this is in practice a really short section, I am guessing on the order of $10 million in initial construction. Additional costs for trainsets and labor as needed.  The Minneapolis-St. Paul region needs to be more creative about the services provided. I am suggesting build the Wye and run 3 Cyan Line trains per hour for a few years. If it works, expand it. If in fact long distance trips from Bloomington to St. Paul are using it, it provides justification for the Riverview Corridor. With a Riverview Corridor, the Cyan Line could be extended along that new track (with additional Wyes where the Riverview meets the Green and Blue lines, respectively), and be transformed into a Circle (or in this case, Triangular) Line.  If not, the region has lost very little.





* Many of the more common colors are spoken for, Cyan is the mixture of Blue and Green.

** Granted stopping at both West Bank station and at Cedar-Riverside Station is not ideal, it is no worse than what happens at much less used stations in Bloomington.


Cross-posted from streets.mn

Temporal Sampling Intervals and Service Frequency Harmonics in Transit Accessibility Evaluation

Recent working paper by my Accessibility Observatory colleagues:

Box plots for sampling strategy performance over all blocks at each sampling frquency. Boxes show inter-quartile range (25th – 50th percentile) with horizontal medial line; whiskers extend 1.5×IQR above and below. Outliers are plotted individually. Mean is indicated by a dot.
Box plots for sampling strategy performance over all blocks at each sampling frquency. Boxes show inter-quartile range (25th – 50th percentile) with horizontal medial line; whiskers extend 1.5×IQR above and below. Outliers are plotted individually. Mean is indicated by a dot.


In the context of public transit networks, repeated calculation of accessibility at multiple departure times provides a more robust representation of local accessibility. However, these calculations can require significant amounts of time and/or computing power. One way to reduce these requirements is to calculate accessibility only for a sample of time points over a time window of interest, rather than every one. To date, many accessibility evaluation project have employed temporal sampling strategies, but the effects of different strategies have not been investigated and their performance has not been compared. Using detailed block-level accessibility calculated at 1-minute intervals as a reference dataset, four different temporal sampling strategies are evaluated. Systematic sampling at a regular interval performs well on average but is susceptible to spatially-clustered harmonic error effects which may bias aggregate accessibility results. A constrained random walk sampling strategy provides slightly worse average sample error, but eliminates the risk of harmonic error effects.

Groper Trains Accommodate a Variety of Tactile Preferences

A recent report from the Maldives Telegraph: Groper Trains Accommodate a Variety of Tactile Preferences:

Building on the success of ladies-only train cars, and singles cars, and responding to complaints from those who felt excluded, a transit agency in Malé, Maldives announced a series of specialized train cars to accommodate a variety of tactile preferences.

To avoid complications, cars are designated by groper’s choice. Travelers will be required to chose whether to be a groper or a gropee, or neither. This will be marked on tickets.

Floors in many train cars will have a blue and pink checkerboard floor pattern to facilitate maximum gropage, where the be-groped (but not groping) are expected to stand on the pink tiles and gropers (but not be-groped) on the blue tiles, while those open to both groping and being groped are on the orange tiles, and those neither groping nor being groped stand on the green tiles. When asked if this was sexist, the agency said “No”.

It is hoped that cars will be evenly used.

Hans Pincher, spokesman for Friendly Hands, the groper advocacy organization, praised this new configuration, but noted sadly that Malé’s  trains do not have 32 cars to accommodate all preferences for people who want to simultaneously grope and be groped without creating confusion.

The following table was published by the agency:

  • M g M & ! W – 1
  • M g W & ! M – 2
  • M g M & W – 3
  • M !g M | W – 4
  • W g M & ! W – 5
  • W g W & ! M – 6
  • W g M & W – 7
  • W !g M | W – 8

“M g M & ! W – 1” should be pronounced as “Men who want to grope Men (and not women) should use car 1. La-de-da.”

M = Men
W = Women
g = grope
b = be groped
! = not
& = and
| = or
X = cannot be accommodated

People who choose to be gropees should use the following cars based on preference

  • M b M, !W – 1, 3
  • M b W, !M – 5, 7
  • M b M & W – 1, 3, 5, or 7
  • M !b M | W – 2, 4, 6 or 8
  • W b M, !W – 2, 3
  • W b W, !M – 6, 7
  • W b M & W – 1, 3, 5, or 7
  • W !b M | W – 1, 4, 5, or 8

Governing transit: the regulated public utility | CityBlock

Alex Block over at the City Block blog writes about Governing transit: the regulated public utility.

The MBTA is struggling, but they’re not the only transit authority facing both near and long-term challenges. The MTA in New York is trying to find the funds for its capital plan; WMATA is facing systemic budget deficits while trying to restorerider confidence in the system.

For-profit corporations such as airlines aren’t the right answer to govern transit in an American context. So, what kind of structure could work?

Writing at Citylab, David Levinson made the case for structuring American transit operations as regulated public utilities, able to pull the best elements of private sector management and pair them with the fundamentally public purpose required for urban mass transit.

David cites seven key elements of this model:

  1. Competitive tendering for services
  2. The ability to raise fares (with regulatory approval)
  3. Using a smartcard as a common platform for fare payment
  4. Specific contracts with local governments to operate subsidized service
  5. Ability to recapture land value through land ownership and real estate development
  6. Access to private capital markets
  7. Local governance, funding, and decision-making

These elements aren’t substantively different from the elements of German public transport governance reforms outlined by Ralph Buehler and John Pucher: competitive tendering for many services, increased fares, investments in technology to improve capacity, efficiency, and revenue. Public regulation oversees these efforts to operate the core business more efficiently.


A One-Track Mind

While at this point, we are almost assuredly beating a dead horse, until the Green Line Extension (Southwest LRT) is actually under construction, there remains the possibility it can be improved. While the best improvement (given the existence of an LRT to fourth ring Southwest suburbs) would be to route it along a path where people actually live, if we cannot maximize benefits, surely we should minimize costs.
I speak of course of the tunnel under the park.

Kenilworth Sections
Kenilworth Sections

The stated reason is the right-of-way is insufficiently wide to accommodate two tracks of LRT, one track of freight rail serving about 3 trains a day, a bike path, and the buildings that were built where it would have been convenient to run some more track.
There are two obvious solutions to this problem which have not been given serious consideration as far as I can tell.

First, the freight and LRT can share the track at different times. The experience with Northstar certain demonstrates why having a few passenger trains on a freight railroad can create lots of passenger delay, but this is different, it would be a freight train on a passenger track owned by the public.

Everyone says “But, FRA”. I realize there are institutional barriers which need to be overcome. Perhaps those are more expensive to overcome than $130 million, or whatever the difference in the surface solution and what the tunnel will cost.

Second, if one-track is good enough for freight, why is it not good enough for LRT for a short section? (This is an idea previously considered by Matt Steele at streets.mn.) This of course is a tight fit, and may require waivers from appropriate regulatory authorities, but is physically possible from the drawing I have seen.

Section B-B
Section B-B

For the sake of argument, let’s assume we want to single track 1.5 miles, with trains going up 45 miles per hour (say an average speed of 30 mph to make the math easy). This would take 3 minutes. The trains are on 10 minute headways in each direction, or one train every 5 minutes through the bottleneck. (Note, Matt assumed 2 minutes, and higher speeds. I am using conservative assumptions).

If timing were perfect, there could be zero delay from this scenario. This is a deterministic case. That is the assumption underlying Matt’s post.

However, as we know, timing is rarely perfect, so we need to look at stochastic delay. Stochastic is engineering jargon for random. Random is engineering jargon for a case where multiple outcomes have an equal likelihood of being chosen (or some are more likely than others, but we cannot be sure that would be the case).

Even when things are random, that doesn’t mean we cannot ascertain the average of the distribution.

Let’s suppose we  have an arrival rate of 1 train every 5 minutes (our arrival rate lambda=0.2 trains per minute), and a server rate of 1 train every 3 minutes (mu=0.33 trains per minute). If the systems is completely random (and we certainly hope it is better than that), we can use stochastic queueing theory to estimate the delay.

Worst case (aside from someone actively and maliciously controlling the trains so they do arrive at the same time (which implies that deterministic solutions with zero delay are possible)), we can model this as an M/M/1  queue (meaning, as wikipedia says: arrivals follow a Poisson process and job service times have an exponential distribution) . This assumes Markovian (random) arrival and departure processes and a single channel.

The utilization rate (rho = lambda/mu) is 0.6, meaning the server is busy 60% of the time.

Math gives us a formula for the average queue size:

Average queue size = rho/(1 – rho) = 1.5

Math gives us a formula for the average wait time :

E(w) = lambda / mu*(mu-lambda) = 0.2/(0.333*(0.333-0.2))=4.5 minutes

At 1 million passengers per month (12 million per year) for 30 years, this is 360 million people delayed 4.5 minutes=1.6 billion minutes of delay. At $20/hour, this is $533 million.

Clearly this value is larger than the cost of the tunnel.

On the other hand, perhaps we only need to single track for 0.5 miles.

In that case, the server time is 1 minute, so mu=1. Capacity utilization is 20% (i.e. rho is 0.2). Average queue size is 0.25 trains. The average wait time is 0.25 minutes.

Our 360 million people are delayed 0.25 minutes at $20/hour is $30 million. This is considerably less than the cost of the tunnel.

The train speeds could be adjusted so no-one would know they were delayed (i.e. trains would slow down approaching the switch, or be held at the previous station, as needed. And remember this is worst case, delay should be less than this with any competent schedule adherence. With perfect schedule adherence, they are indeed zero (our deterministic solution).

Single-tracking is a solution to high capital costs. It is not optimal, it has delay costs  that depend on the length of the stretch, headways, how much control Metro Transit has over running times, and so on.

Everything involves trade-offs.

There is of course a concern about running LRT next to (near) freight trains, carrying lots of explosive ethanol. I say, don’t do it. Run them at different times, even if on different tracks. If freight trains are only permitted at night, or in a mid-day window when an LRT is held upstream of the pinch-point for a few minutes, or ideally in a scheduled break, there should be zero chance of collision. There is always a chance of derailment – that doesn’t change, but derailment is less hazardous than collision for what I hope are obvious reasons.

In the long run, maybe freight will go away (e.g. once people stop using ethanol), go somewhere else, or another solution will be found. At that time, the line can be double-tracked if needed.

In the short term, the money saved could be used to temporarily relocate the trail to quiet residential streets nearby, compensate the neighborhood, give money to the Park Board, or any number other socially worthwhile goals.

Crossposted at streets.mn.

NCITE/ITSO Joint Meeting: October 22: BRT at Metro Transit

The NCITE October Section Meeting will be held on Wednesday, October 22nd at the University of Minnesota – Coffman Memorial Union in the Mississippi Room (3rd Floor). It will be a joint luncheon with the U of M Interdisciplinary Transportation Student Organization (ITSO).

Katie Roth and Christina Morrison from Metro Transit will be speaking on upcoming Bus Rapid Transit (BRT) projects and studies. This meeting is a great opportunity for members and students to meet and build networks, and learn how an emerging network of BRT lines will improve connectivity and mobility throughout the Twin Cities region. Coffman Union is well served by the Green Line and multiple bus routes.  Parking garages are also available nearby.


Place:          University of Minnesota – Coffman Memorial Union

Mississippi Room (3rd Floor)

300 Washington Avenue SE

Minneapolis, MN 55455

Phone (612) 624-INFO (4636)

Directions and Parking Options



11:30 a.m. – Noon Registration

Noon – 12:30 p.m. Lunch

12:30 – 1:30 p.m. Business Meeting and Presentation


Registration: Please click the following link to register or RSVP for the event before 10/20:



Cost: $20 members and guests ($5 students).  Webinar access is available at no charge.


“It’s a success”

There are no more common words to hear shortly after the opening of a new rail project in the United States than “It’s a success”. The forecast of the declaration of success is far more accurate the forecast of ridership or costs.

For instance, Metrorail (WMATA) claims:

Metro: Silver Line ridership remains strong

Metro today provided updated Silver Line ridership information showing that, less than two months after opening, the new line is already performing at 60 percent of its projected ridership for the end of the first full year of service. As of last week, an average of 15,000 riders are entering the system at the five new Silver Line stations on weekdays for a combined 30,000 trips to or from the new stations.

In the planning process, Silver Line ridership was projected to reach 25,000 boardings at the five new stations after one full year of service.

Metro estimates that the Silver Line is currently adding approximately 6,000 new riders — making roughly 12,000 trips — to the Metrorail system each weekday. The balance, approximately 9,000 riders, are primarily former Orange Line riders who have switched to the Silver Line.

Some outlets have used the word “success” to describe the line, as has Secretary Foxx. Certainly it is still early, and maybe the Silver Line will exceed first year forecasts, or final year forecasts, or even have benefits in excess of costs, or somehow reduce inequity in the Washington region, or lead to economic development, or any number of other objectives hoisted on transit lines. It is arguably successful from a project delivery perspective, in that it was delivered, and opened for service, but that seems a narrow way to think about success.

In contrast, another new start, Metro Transit’s Green Line, has done a bit better, even with all sorts of traffic signal timing issues. It too is heralded as a success, with ridership exceeding forecast year ridership about 3 months in.  While many of its riders were transfers from existing bus services, it clearly is serving more new people for less money than the Silver Line.

Which is more successful? Which is a better investment? Time will tell, and I will leave that to the reader’s judgment.

I have two hypotheses as to why these words are so common.

First, it may be that all projects are successful. For this hypothesis to hold, we would need to see enormous transit market share across the country after several decades of more than 20% of all transportation funding going to transit (figure 2, but also this). Sadly the evidence suggests otherwise.

Alternatively, it may be that the appearance of success is important, independent of the actual facts on the ground. Calling “success” aligns you with “Team Rail” and rewards your supporters. The illusion of success is critical to obtain future funds. No one wants to give money to an agency that actively (if honestly) claims “It’s a failure” or “It’s a disappointment”, or “We’re still perfecting it,” or even “It’s a hobby“.

I hold this latter explanation as more likely. This is not to say there are no successes in urban rail transit. There are many. Starting in 1863 with the  London Underground, rail transit globally had an extraordinarily good run for 60 years. In the US, it sort of petered out after that for the next 50 years or so, though in other countries, rail transit has continued at various levels of strengths.

Some of the lines in the past 40 years have been more successful than others, all depending on your definition of success. (For instance, a list of LRT systems by ridership per mile is here.) The best systems remain the ones built in the early 20th century, with only LA’s Metro Rail breaking the top 5 in riders per mile (and DC’s MetroRail coming 6th).  Yet as far as I can tell, all new systems have been declared successful by somebody (even the relatively low ridership per mile lines like Tampa’s TECO line, or Charlotte’s Lynx). Some are even pre-declared, like The Tide in Hampton Roads.

I find it hard to see billions being spent on the Silver Line so far to add 6000 riders (12000 trips)  as an unqualified success, (I would find it hard to see meeting these low forecasts as a success either). This is more $ per passenger than many commuter rail lines spend, which few outside the agencies themselves are calling successes (the advocates of course do use that exact word).

If spending $2B added zero or negative riders, that would be truly surprising, indicative of active destruction of money. I will just state there were plausible alternative uses of the funds that would have improved society in other ways. Every expenditure has an opportunity cost.

Do not believe or repeat the press releases of agencies and advocates uncritically.



The Transportationist is on MPR’s Daily Circuit. Today 10 am Central.

I got invited back.

I will be having a live in-studio conversation with Kerri Miller on MPR’s Daily Circuit Today (Tuesday October 14 at 10 am Central Time). The other guest is  Adie Tomer of the Brookings Institute/Metropolitan Policy.

Topics are likely to include transportation issues in the midterm elections,  big ideas for transportation’s future, how those ideas get paid for, and who the constituents are in that conversation.


In the Oct. 9 gubernatorial debate, Gov. Mark Dayton and his two opponents named transportation on their list of priorities for the next four years.

Dayton proposed a gas tax increase to pay for his transportation plan, but how to pay for all that’s needed for roads and bridges is a problem that vexes politicians nationwide.

On The Daily Circuit, we talk with two transportation experts about the economics of transportation planning.