« information request: peaking patterns | Main | disasters can raise your taxes »

TrackBack

TrackBack URL for this entry:
http://www.typepad.com/services/trackback/6a00d83454714d69e20148c7a2efdc970c

Listed below are links to weblogs that reference beyond "transit scores": an exchange with matt lerner:

Comments

Feed You can follow this conversation by subscribing to the comment feed for this post.

D

Hi Jarrett,

Halcrow, the transport/planning consulting firm that I work for, has done just this sort of analysis, developing an 'accessibility index' that could then be used to assess the impacts of various transportation policies (infrastructure investments, but also travel demand management (including road pricing, parking charges, etc) and transport-related land use policy changes).

I'm checking internally to see how shareable that experience is (it's ongoing work that hasn't yet been finalized by the client), but hopefully I can send you a methodology within the next couple of days.

The one caveat is that it is survey and model based and not as fine-grained as an address-by-address approach. It's a bit more 'policy' oriented, as a result, rather than 'property' oriented.

Christopher Parker

But real estate value is very much about symbols, not utility. If it was about utility the quality and efficiency of your furnace would affect home value -- but it doesn't.

Of course the transit score will itself become a symbol, like tax rates.

Also mobility and quality of transit are not the same thing. The public evaluates rail transit as higher quality even if the seat and the frequency and the amenities on the tram is the same as the bus.

Brent

This reminds me of a report that was issued by the Martin Prosperity Institute before Toronto's 2010 mayoral election. It raises the concept of "transit deserts" in the inner suburbs. Unfortunately, while they might have been onto something, the concept is spoiled by a similar weighting:

The map above illustrates the intensity of transit service in the City of Toronto by census tract. It was produced using publicly available data from the Toronto Transit Commission. The shading is determined using a unique formula that considers the service level at timed stops (measured as the average number of stops that a streetcar, bus, or subway makes per hour), which is then weighted by transit type (where subway=1, streetcar=0.5, and bus=0.25) within 1 km of the census tract’s centroid. Once again, the areas best connected to transit are located downtown, in close proximity to both the subway system and frequent streetcar service.

Of course, you can see the shocking revelation that, when you give a higher weighting to streetcar routes than bus routes, areas with streetcar routes fare better than routes with bus service! My goodness.

I like the travel time methodology better myself, and I think it's closer in spirit to what WalkScore is intended to do: basically, see how much "stuff" can be reached within a reasonable walk from a given destination. The difference is that, for a given network, walking speed is pretty uniform, so it doesn't matter whether you talk about distance or speed. Transit is much more complicated, involving travel speed, route frequency at different times of day, usefulness of route (it doesn't matter if I'm next to a north-south subway station if I work in an employment area to the west), etc.

Perhaps another key difference is that WalkScore is all about daily amenities that one would expect to have nearby for a neighbourhood to be walkable — grocery store, pharmacy, restaurants, libraries, etc. — whereas for a transit score, these uses are secondary to the commute trip. So a transit score might be a weighted index that compares the number of jobs with the travel time required to travel to them.

It strikes me that, between the WalkScore and Mapnificent analysis methodologies / algorithms, there must be a happy medium that accomplishes this.

Brent

By the way, another use for a Mapnificent-style analysis.

Back in the 1940s when Toronto was planning its rapid transit network, the TTC prepared a pair of maps that were essentially heat maps showing travel time contours from Yonge and Queen (main downtown intersection) to all points in the city. (It wasn't that far off from what you would see if you compared Mapnificent maps prepared in 5-minute analysis intervals.) The map on the left showed travel time contours with the then-current system; the map on the right showed the predicted travel time contours once the rapid transit network was completed. It was an effective way to show the real benefits that riders would experience.

It would be interesting (and, with today's technology, whether GIS or Google, surely easier) to use a similar technique show what the impact would be with various LRT proposals today.

Joseph E

"Find me an apartment within 30 minutes of work on transit"

This is exactly what I want. Well, and another one for bicycling.

It took me many hours of searching to first find the areas accessible to work by transit (especially since my wife and I both had different places to get), and then search for apartments within that area. If this process could be automated, that could be worth $100 to me, next time I move.

Commuters also care about reliability

Hi Jarrett, while you are correct that there should not be an arbitrary weighting by mode, it is entirely relevant to weight services by reliability. For example, a fully grade separated service, whether bus or rail, is much more likely to have a high on-time performance, while transit in mixed flow traffic lanes, whether whether bus or streetcar, may exhibit a greater variance in wait times for the rider.

The weighting factor could be based on the likelihood of delay and the range of delays, using actual data.

JJJ

I completely agree with Joseph. I may be moving to DC, so Ive been getting a general idea of apartment pricing....but I also have to look at google maps + badly designed transit websites to figure out if a certain area is within 30 minute of the potential job site...and then later I'd have to also factor in supermarket access. It's a giant PITA. Mapnificent is a good start, but it could be even better.

Tom West

As Jarett points out, TransitScore's current algorithm uses mode as a proxy for speed. Rather than assignign arbitrary weightings, it would be better if TransitScore looked at the average speed by mode for a given transit system, and used the relative speeds to generate the weightings. (So if a given mode is twice as fast as bus, then it would get a weighting of 2).

Christopher Parker

As I think about this, the key is to get the algorithm right. For better or for worse, most people value rail over bus. But maybe not as much as .5 vs .25. Yes, speed counts, and frequency. Quality of ride counts too - seat quality and harder to define like how clean the stations are and if I have to stand out in the cold at a bus stop or can wait indoors on a bench. Perceived safety counts (more than real safety).

Chris

Before you rely on Mapnificent you need to make sure it includes all transit systems in its calculation. For example, the Mapnificent for Los Angeles does not include services operated by Long Beach Transit, which would make the unsuspecting user think that if they lived in Long Beach they would mostly have non-existing transit options.

Anc

Has the "transit travel time tool" not been updated for Link in Seattle?

Nicholas Barnard

From what I'm seeing the Transit Score is using mode as a proxy for frequency. Why not go through each individual route and come up with a frequency score for it the individual route, then use this within the mode calculator. Since transit schedules change only three or four times a year this isn't that much additional calculation..

The comments to this entry are closed.

the firm

Jarrett is now in ...

Related Posts Plugin for WordPress, Blogger...
Related Posts Plugin for WordPress, Blogger...