Is the Usual Share of a Commuting Mode always Greater than its Actual Share?

摘要

Using data from the 2001 National Household Travel Survey (NHTS), recent research showed thattransit's usual share is greater than its actual share for workers in the U.S. for a variety of commutermarkets. A mode's usual share is the percent of workers who state that they usually use that modefor commuting in a week while the actual share of a mode is the percent of work trips by that modeby the same workers on a typical work day. This paper explores if this relative relationship betweena mode's usual and actual shares holds true for common modes other than transit for the U.S.Mathematically, the paper determines that this relative relationship cannot hold true for all modes; inother words, the usual share has to be smaller than the actual share for one or more modes other thantransit. Empirically, it uses the same 2001 NHTS to test this relative relationship for three commonmodes (POVs, walk and bike) and for a variety of commuter markets. The empirical results confirmthe mathematical conclusion with the relative relationship being true for bike but not true for POVsand walk. In addition, the relationship between usual and actual shares is determined not solely bythe mode but also by individual commuter markets. Finally, the deviation between usual and actualshares in percentage terms is large for transit and walk, but small for POVs and bike. One directionof future research would be to determine the reasons of these differences in the usual-actualrelationship across modes and commuter markets.