Rapid Stats

New transit landscape

I guess I’m not delivering them very rapidly, but I thought it would be useful to enter the data from Metro Transit’s Rapid Bus Corridor concepts into one spreadsheet.  The individual corridor sheets are beautiful and packed with facts, but the advantage to a spreadsheet is easy comparison of one corridor to another.

The reason we must compare corridors is that Metro Transit isn’t necessarily planning to build all of the corridors they developed concepts for, and some will be built before others.  Part of the purpose of the study is to develop “a prioritization plan for the arterial corridors”.  That language comes from SRF’s summary, but apparently we will have to wait until the study is published in February to know exactly what the prioritization will be based on.

In the meantime, we have the stats from the corridor concepts, which we can assume will be used to prioritize (as opposed to political prioritization, i.e. regional balance – we already know that Scott County is not in the running).

Demographics

One place to start is to just look at the number of people who live or work along each corridor.  Metro Transit gives us these numbers both in a 1/4 mile circle and a 1/2 mile circle around the proposed stations for each rapid route.  The raw numbers are of course weighted toward lines with more stations (the number of stations runs from 15 on Hennepin to 28 each on Nicollet and Chicago), so I created a “density” measure, which just divides the total by the number of stations for a more fair comparison.

On the above chart, like the next three, the scale is distorted by the high number of jobs in Downtown Minneapolis.  To offset this, Metro Transit included a metric for jobs outside the downtowns, although in reality the downtowns are the largest trip generators and should be considered.  As you can see, Chicago really places well in this chart, coming in first in jobs (thanks to an added boost from the Mall of America) and also in population.  Nicollet and Lake are close seconds in population, and Central, Nicollet, Broadway and Hennepin also get job boosts from Downtown, although each follows its predecessor by 10k jobs or so until Hennepin finishes with 60k jobs fewer than Chicago.  Presumably this distance mostly stems from proximity to the core, as the different routes vary much more slightly in jobs outside Downtown.

The Mickey's station on West 7th has the highest grease density of any corridor

The above chart shows a slightly different picture, with the same five Downtown Minneapolis-serving lines appearing at the top of the heap again, but in a different order.  In this measure American and West 7th rank close to the Downtown Minneapolis lines.  These lines still have fairly high job numbers (though less than half of Chicago’s), but are helped by their much lower number of stations per mile – American has the least of any corridor, with 1.33 stations/mile, and West 7th is just behind it, with 1.42 stations/mile (see table below).  That means they don’t waste time serving low-density stations, like most of the other corridors do generally as they get further from the downtowns.

Making the circle a bit wider makes some sense – though the typical walking distance to transit is 1/4 mile, people are usually willing to walk further to faster service, and 37% of Hiawatha riders walk more than 1/4 mile.  But the chart above doesn’t show a drastically different picture.  The y axis is larger, but the corridors mostly seem to rank in the same order, as is more evident when you apply a color scale to the data in a table:

The table above is a good way to finish the series on demographics, because it clearly shows which routes have the advantages in the various demographic categories.  Nicollet and Chicago have the advantage both in jobs and population, and although they have some competitors in individual categories, no other routes are competitive across the board.

But for consistency I’ll present this last chart above, which shows that the most bang for the buck will probably come from the Hennepin line.  That’s the one where every station built is likely to reach a high amount of riders.

Station Spacing

An interlude about station spacing – the corridors all deviate from the half-mile station spacing ideal.  In many cases this is due to traversing either of the downtowns on a N-S axis, where the stations are often placed two blocks apart (where they currently stop in Downtown Minneapolis).  However there are a number of factors, for example Central has 3 stops in the half-mile from 18th to Lowry to serve the higher-density neighborhood; similarly, the routes that run between Franklin and Lake have 4 or 5 stops in that mile.  The opposite is the case with East 7th, which generally keeps to half-mile spacing, but leaves more than a mile without a station between Arcade and Clarence.

The stations depicted on the concept corridors are not final, of course.  But it seems as though Metro Transit prefers to keep the much closer spacing downtown, which makes sense because most of the lines terminate there anyway, so it’s fair to trade travel time for coverage (plus they’re apparently sinking some money into bus stations on 5th and 6th in St Paul anyway, a factor that may help the 7th St corridors).

Speed, Frequency and Reliability

Demographics are not the only factor to consider when prioritizing implementation.  Instead it’s important to consider the degree to which the routes will be improved by the enhancements.  Pretty stations are nice and all, but what I care about is how fast I can get to Mickey’s.  To that degree, Metro Transit included measures of speed, frequency and reliability in its rapid bus concepts.

A number of the proposed rapid bus enhancements should improve on-time performance, but maybe Metro Transit found it hard to quantify or predict, because they only included the on-time performance for current locals in the concepts (shown in the above chart).  From this, we can glean the lines that are most in need of improvements; Central rises to the top by virtue of its placement at the bottom.

The only clue Metro Transit gave us as to the increase in on-time performance was a series of pie charts showing the factors of travel time for each route.  I’ll admit that I’m not sure how to process this information, although generally it seems right to look for an increase in “In Motion” time and a decrease in “Dwell Time”.  (Since these are percentages, an increase in “In Motion” doesn’t mean the trip will actually take longer.)  Part of my confusion stems from the two factors that aren’t listed for all routes – especially that those factors disappear from the projections for after improvements are made.  It makes sense that “Hold/Other” would disappear, since holds are mostly scheduled to make up for delays.  But how can they expect that traffic delays will disappear?  Maybe if they were including dedicated bus lanes in the scope of this project, but my understanding is that’s off the table.

Assuming Rapid Bus routes are pretty reliable, they should be quite a bit faster – between 5 and 30% faster.  That 5% is for the already limited-stop West 7th line and is a much smaller improvement than most lines, implying that much of the speed increase comes from wider stop spacing.  Chicago, Central and East 7th are also outliers in this measure, all improving by around 10% (the rest of the routes improve by between 20 and 30%).   Presumably Central’s improvement is small because the 10 already uses signal preemption; East 7th and Chicago are a mystery to me.

Disclaimer about the above chart:  the % change in travel should actually be negative, but I changed it to positive to get it show on the chart.  Technically I shouldn’t use a line graph to show a nonlinear measure, but this is the best way I’ve found to get different y axis measures to show up in Excel – if you have a better idea, please let me know.

That last disclaimer should probably also apply to the above chart, too, but I’ve always wanted to use a radar chart and it seemed to fit pretty well for comparing frequency.  I was able to calculate effective frequency for the proposed corridor by simply adding the proposed rapid and local frequencies.  Assuming they will not be scheduled to bunch (i.e. to make the local bus show up as close to the rapid bus as possible), these routes will have really impressive frequency – 6 corridors will have 6 minute headways or less.  Hennepin will end up with an effective headway of 4.3 minutes, with a rapid bus every 7.5 minutes on top of locals still running a respectable every 10 minutes.  The radar chart shows the biggest improvements in the American and Broadway lines, where current 30 minute headways are halved to every 15 minutes.  In the case of Broadway it’s a bit misleading, though, since the densest part of West Broadway – the mile between Knox and Washington – will retain local bus service, although at what frequency they don’t say.

Busing for Dollars

Another factor presumably will be the cost of construction.  This will be relatively low, but how low seems to be unknown – the presentation on Metro Transit’s site suggests $1-3m per mile, but a subsequent Star Tribune story says it could be as much as $6m per mile, and today’s MinnPost article quotes a Met Council rep as estimating $2-5m per mile.  Probably inertia is causing them to estimate the cost per mile – since there are no guideway improvements under consideration, a per station estimate would be more useful.  Apparently Metro Transit is considering large and small station concepts, and presumably there would be a hierarchy of stations, with high-boardings stations getting large stations.  If that’s the case, you couldn’t just assume that routes with more stations will be more expensive, since for example the Lake St route, with a high number of transfers, will have a higher per station cost.  On the other hand, because the highest boardings tend to be downtown, maybe routes that serve the downtowns will have the highest per station cost.

Conclusion?

With uncertainty still surrounding nearly every detail about the Rapid Bus concept and corridors, maybe the only thing I’ve proven with this exercise is my obsession with transit.  However, the evidence strongly suggests that each corridor has unique factors that necessarily be boiled down to a set of numbers.  After all, with one exception these lines all currently serve tremendous numbers of riders, so where ever improvements are made it will improve a large number of rides.

Personally, I tend to favor improving network connectivity, which could boost routes like American or Snelling that (will someday) connect light rail lines.  Other considerations, such as improving underserved areas, would boost the Broadway or East 7th lines.  As long as we’re speculating, we may as well hope, and I for one hope they just build them all at once.

Numerical Afterword

As I mentioned, all the charts in this post were made with Excel, which was the ideal tool for me only because its crudeness so well matched my own ineptitude.  I’ve always enjoyed visual presentations of information, but never really had the training or talent for it.  So if anyone reading this has any constructive criticism, please don’t let your Minnesotanism hold you back from commenting.  Also, if anyone has any suggestions for better chart-creating software than Excel, please share.  Finally, I want to spread the fruit of my data entry – apologies for the mess.

 

4 comments on “Rapid Stats

  1. mulad says:

    Heh, the thing that sticks out to me about the charts is that radar chart — typically you want the various axes(?) to represent attributes and each line to represent a single entity (route), but you’ve got it the other way around.

    As for cost per corridor… Whoever said $6 million must have been thinking of regular BRT with exclusive lanes and whatnot.

    The cost of priority signaling would be based on the number of signals along a stretch of road, not necessarily distance or number of stops (presumably Lake Street would have the biggest cost here). Of course, some signaling improvements could be made even without going to the level of having priority signals installed — Mike Spack says that “Improving signal timing has about the best benefit/cost ratio of any improvement the traffic engineering community can make.” The city of Minneapolis is also moving forward with replacing their old citywide signal control system with one that could potentially prioritize buses. I got the sense that it used GPS feedback from devices already on the buses rather than relying on something new, so there’s potential that it could be implemented for very low cost — a few million dollars for the entire city. However, given how unreliable NexTrip can be sometimes, I’m not sure if the GPS transcievers report back with enough frequency and precision to actually be effective in triggering lights to turn green. Some physical changes to the signals themselves might still be needed.

    Station costs could be reduced a bit by purchasing as many as possible and making use of economies of scale in assembly. Ideally they should be fairly modular, using the same components and segments whether they’re large or small.

    Hmm, well, enough rambling for now…

    • Alex says:

      Dang, I thought I’d finally captured the elusive radar chart. Seems like you need a very specific and unusual data set to get that thing to work. Well at least it broke up the bar chart monotony.

      It would be interesting to see a stoplight density map of the corridors. I can’t find a recent cost estimate for signal prioritization, but I imagine it’s on the low end of the 2002 $8-35k per intersection estimate (http://www.itscosts.its.dot.gov/its/benecost.nsf/ID/478B21EDD18C9EAE85256DB100458929?OpenDocument&Query=CApp). Seems like that would make it a small fraction of the station costs.

      Another factor in station costs that are unknown at this point is whether they’re going to try for additional right-of-way. It looks like they’re trying to make the stations as skinny as possible, presumably to avoid this, but a lot of these corridors have pretty narrow sidewalks, so it might be tough to squeeze the stations on there.

      • mulad says:

        Ideally I’d like to see bulb-outs used as much as possible, which would alleviate the need for more right-of-way and open up the sidewalk at the same time. There would be some places where that isn’t feasible, however.

  2. natybee88 says:

    Quick chart request: please label your axes! I just want to make sure I know what I’m looking at. Thanks!

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