The census has collected some information on the trip to work from a sample of Americans since 1960. The data from this survey has varied in quality of time, geography, and detail since then, but lately has been packaged in the questions of the annual “American Community Survey” (ACS). I prefer the long form survey from the 2000 census, as the publicly available data got all the way down to the tract level and differentiated bicycle trips from “other”. As far as I can tell, the ACS groups bicycling with motorcycling and “other”, and there’s no prying them apart.
The data I present here is about “mode choice”, the method of getting from home to work most mornings during the week. “Worked at home” is included, and growing, but I’m not concerned with that today. I am focused on comparisons between walking, biking, traffic, and transit. If we must leave the house, how do we get around?
There are two problems with journey to work as a measure. First, we might not use just one mode of transportation to get to work. We could walk a long way from parking to our job, park at a park and ride and take a bus on highways in, walk to transit and take a bike-share bike from the station work, or drive in the morning and carpool back in the evening on alternate days. The question of one mode of journey to work supposes that we can move directly from our homes to our jobs , a convenience most enjoyed by walkers, bikers, and traffic. The other problem with journey to work is that it is only about 20% of the travel that we do, by distance. This is kind of unfair, as 30% of the miles we do travel are on irregular long trips over 50 miles in length.
However, the journey to work is most important, and best to measure, because that is when we feel the pain of traffic. Roads, sidewalks, bike trips and transit stops and stations are sized to handle that peak volume. When 20% of the rips happen in 10% of the clock, traffci gets crowded, congested, and unhappy, even if it is safer than during free flow.
What about biking, walking, and transit? I’ve long been amused by the claim that metro New York’s traffic use is almost as high as Houston’s. Taken over all trips, for the whole metro, this may be true. But focusing from state to metro to city to even census tract levels, we find that walking, biking*, and transit generally get more and more use the closer we get to the city. To almost un-American levels, even.
If you look even closer at cities and the “journey to work” statistic you see hundreds of places where walking, biking, or transit are over 10% or even 50% of the work trips. I started out looking into these graphically in google Earth, but saw that there were way too many to snapshot. If you’d like the .kmz file, just ask
Census Tracts and Households with supernormal non-traffic mode share, 2000 Census.
Thursday, I’m going to talk more about the NHTS and “where did our trips go?”, this time by looking at the age data. I knew there was a reason I downloaded that 8,000 line spreadsheet.
* And motorcycling and other, per the ACS