Friday, April 25, 2008

Carless in Dayton

Not having a car consigns one to economic isolation in a place like Dayton, where only 2% of commuters use public transit. But there are suprising concentrations of carlessness in the metro area.

The 2000 census provides a snapshot of the situation. The census measures the number of occupied housing units without access to a vehicle, which seems like an odd way to count carlessness. But one could use this as an indirect proxy by saying occupied housing unit = household (more or less). The census provides these numbers by tract.

Mapping Carlessness

So, counting up the tracts, coming up with a percentage, and then arranging them from lowest to highest, one can ascertain breaks and clusters of carlessness. The median is 6.3% carless units per tract, but there are some big concentrations, particulary downtown, where a whopping 70% of the units are carless, probably do to the concentration of senior housing downtown.

Then a collection of higher tracts, mostly close-in areas, then some lower breaks. After a plateau things go on a slow slide down to zero.

Mapping it out to the median value, one sees some concentrations, mostly in west and east Dayton, but also out in Drexel and up off of Dixie in Harrison Township, and one just south of Dorothy Lane in nothern Kettering. The little apartement cluster south of Town & Country also appears.

Taking a close up of the city, and noting the highest tracts. One can see that at least two are the sites of large public housing projects. Laying in the assumed route of the propose streetcar, one can see it doesn't go where the presumed market would be, aside from downtown. One would think a streetcar up West Third or along US 35 somehow would make more sense given the high % of carless housholds here.

Transit Commuters

The census provides a projection based on a count of riders per tract, number of transit and non transit commuters (16 years or older who use public transit to get to work).

Its interesting that in this case the commuters don't necessarily overlap with high % of fact only the "West Old North Dayton " area (Parkside Homes) appears in the highest cohort for carless and transit commuting.

There are some pretty clear breaks here at around 100 riders per tract. I identify two clusters above the 100 rider break, and two below.

Then, mapping it out. In this case Oregon and South Park appear in the top rider tracts, but also the neighborhood around Lexington Avenue and neighorbhoods around Salem Avenue.

Due to the large population size some south suburban tracts show up as well, with a slight concentration of riders in the apartments between Alex and I-75 near the Dayton Mall.

Now, doing a quick and dirty correlation between high carless and high transit usage to come up with some tracts that rely on public transit. All are more ore less in the city

Expanding the map, one sees Westwood,the neighborhoods between Salem and Main, Lexington Avenue, Lower Dayton View, Desot0-Bass & Parkside Homes areas, Inner East, South Park/Oregon, and, interestingly, the old "interurban era" plats on North Dixie in Harrison Township.

Laying in the streetcar route, it again doesnt seem to help much except for downtown and maybe South Park.

Travel Time

The census also provides some interesting projectsion for travel times. It groups riders by whether they take public transit or "some other" form of commuting (which probably means car in Dayton's case, but could mean walking or bike), and then by how long it takes them to get to work (and from work), from 30 minutes or less up to 60 minutes or more.

So one can see some very interesting patterns here, mainly that it if time is valuable its best to not to rely on public transit. A whopping 70% of "non transit" commuters take 30 minutes or less to commute. Only 6.4% take more than 45 minutes.

How does this play out for transit users in areas of high transit commuting?

Here are the groupings of tracts, with % of commuters by travel time shown as pie charts. In all cases it takes 35% or more of commuters a trip of 45 minutes or more to commute to work.

The aggregating of percentages masks some worst cases. In the case of that small tract near the Dayton Mall, 503.03, all the transit riders had a trip of 60 minutes or more to work.

Due to the "edgeless city" dispersed suburban auto-centric development patterns of both manufacturing and service work public transit doesnt work well, requiring lots of transfers. Lack of frequency also adds to travel time as due to infrequent headways (plus a viscious cycle as people avoid transit due to inconvience, leading to more route and schedule cutbacks, leading to more transit avoidance).

One wonders if it would make more sense to scrap scheduled routes and default to an on-demand or ad-hoc jitney system.