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The Cost of Slow Travel

One of the most widely cited numbers in contemporary transportation media coverage and policy discussions is the cost of congestion estimates that Texas Transportation Institute (TTI) annually produces as part of the Urban Mobility Report series.   The 2009 version of that report (http://mobility.tamu.edu/ums/)  shows an estimate of the cost of congestion of $87.4 Billion for the top 439 U.S.

Steven Polzin | June 4, 2010, 7am PDT
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One of the most widely cited numbers in contemporary transportation media coverage and policy discussions is the cost of congestion estimates that Texas Transportation Institute (TTI) annually produces as part of the Urban Mobility Report series.   The 2009 version of that report (http://mobility.tamu.edu/ums/)  shows an estimate of the cost of congestion of $87.4 Billion for the top 439 U.S. urban areas in 2007.  That estimate is composed of approximately $8.5 billion in wasted fuel costs, $14.57 in commercial vehicle congestion costs and $64.3 billion in personal time loss congestion costs.    

The same TTI report indicates the 439 urban areas have approximately 56 billion annual passenger miles of travel on public transit.  2007 National Transit Database (NTD) indicates transit vehicle speeds of approximately 13.4 mph while the 2009 National Household Travel Survey (NHTS) data indicates a door-to-door speed for transit travel of approximately 12.2 mph.  2009 NHTS data indicate roadway travel speeds averaging approximately 33 mph.  Using 12.2 mph for transit travel speed and assuming no differences in trip circuity (in reality the less dense transit network is likely to have slightly longer average travel distances for a given origin-destination pair), one can derive an estimate of the "extra" travel time required for using transit. 

Transit's slower average travel speeds result in approximately 3 billion hours annually of additional travel time.  If valued at the TTI time value of $15.47 per hour, this equates to approximately $44 billion annually in lost productivity due to travelers having or choosing to use transit.  Thus, the few percent of persons who use transit (approximately 2% of total person trips are on transit {5% of work trips} and approximately 1% of person miles of travel) incur 70% as much lost time relative to driving as is incurred by the total of auto travelers due to congestion, $44 billion for transit users versus $64 billion for driving in congestion. 

While one often hears about the "cost of congestion", there is virtually no one talking about the "cost of using slower modes of travel".  We hear a lot about the value of having a choice of modes but increasingly little about the value of having a choice of an uncongested or less congested travel option.  Is it fair to talk about the cost of using transit as $44 billion in lost productivity?  And what is the time cost of walking and biking versus alternative modes? 

Obviously these simple calculations do not capture all the interactions between modes or between land use and transportation that might occur with any changes in mode shares.  Also, the respective "costs" could arguable be recalculated with more accuracy using different time value assumptions or more geographically and temporally disaggregate data.  Nor does the data suggest I am recommending we should be discouraging the slower modes – in fact I am working hard to make alternative modes more attractive and competitive.  But it does hint that travelers are, in fact, rational beings and weigh factors that the planning community often neglects in much of the contemporary policy talk about modal performance and impacts. 

If time has value to travelers then it should have value regardless of the mode of travel.  While one could conjecture on the ability of travelers to use part of the transit travel time productively or divert the discussion to environmental or other impacts; transportation policy makers need to take the travel speed implications of various transportation policy initiatives into consideration if they are sincere in taking a holistic approach to evaluating transportation policy options and consequences.  Speed won't win in some of those policy tradeoffs but its importance to travelers and productivity should be appreciated.

One of the reasons the country and individuals have become more productive and the country has had growing gross domestic product over the past several decades is that we have been highly mobile and travel has gotten faster until recent years.  Part of the reason for faster travel has been the shifting from slow to faster modes and facilities.  There are lots of good reasons to enable and encourage use of alternative modes but analysis of the consequences should strive to be objective about the travel time and productivity consequences. 

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