http://chica.com Fri, 10 Sep 2010 06:48:15 +0000 http://wordpress.org/?v=2.9.2 en hourly 1 http://chica.com/how-travel-time-and-cost-become-substitutes-or-complement/278/ http://chica.com/how-travel-time-and-cost-become-substitutes-or-complement/278/#comments Wed, 18 Nov 2009 00:54:38 +0000 http://chica.com/how-travel-time-and-cost-become-substitutes-or-complement/278/ If we have travel time and travel cost, under what conditions can they be considered as substitues? Under what conditions can they be considered as complements?
Could you please give example in transportation system?
Thanks.

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