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This continues last Friday’s article on trip changes between 1995, 2001, and 2009.  I wanted to look at the age patterns of changes in traffic, walking, and biking trips.  The only direction I would go in the future is in trip purpose, as the NHTS distinguishes between work, errand, and play trips.  However, that is yet another level of complexity, and I’d prefer to present this in digestible posts.  There are also many unnerving holes in the data at the trip purpose level which make a comparing purposes across modes and years difficult.

As I was assembling the data for this post, I realized the NHTS periods were a blessing.  1995-2001 was one of the most prosperous periods in America’s history, while 2001-2009 was punctuated by one of our greatest economic collapses.  Trends in transportation modes could loosely show how Americans would respond to times of plenty and want.  Confounding this, the first Transportation Efficiency  Act was passed in 1991, finally allocating a small pot of money (<2% of the federal transportation capital budget) to biking and walking facilities.

I looked at the trip numbers for all trips less than 4 miles in distance.  These are trips that could reasonably be traveled by bike, but are mostly taken in traffic.  

I looked first at the percent change in traffic, walk, and bike trips  for each of the age groups between 1995-2001 and 2001-2009.  Traffic’s trip numbers did indeed fall for those younger than 40, but more dramatically in the more prosperous 90s.  Biking fell even more than traffic in the 90s for the younger ages, but gee dramatically for ages over 40.  Walking trips grew dramatically in the 90s, but less so in the 00s.  Overall, this does show a youthful shift away from traffic, a resurgence of walking in both periods, and an increase in biking only in the 00s.



I am interested in the shift of trips away from traffic and towards “human” modes of transportation.,  Percent changes do not tell this story, because the numbers of trips by traffic dwarf the numbers walking or biking.  A 1% change in traffic would be greater than a 10% change in walking.  I am less satisfied with this graph, but I wanted to show the balance of traffic and human trips  per age group.  This shows a youthful shift away from traffic, and an overall increase in trips at middle age.


While getting these numbers together, I saw that I needed to account for population numbers in each age group.  Using age distribution from the 1990, 2000, and 2010 census, I found the average number of trips per year for the average person in each age group.  This is striking, showing a general decline across most age groups for traffic and a general increase for walking and biking.


Please excuse the logarithmic scale