The Downs-Thomson Paradox with responsive transit service

Fangni Zhang, Hai Yang, Wei Liu

Research output: Journal article publicationJournal articleAcademic researchpeer-review

67 Citations (Scopus)


Downs (1962) and Thomson (1977) suggested that highway capacity expansion may produce counterproductive effects on the two-mode (auto and transit) transport system (Downs-Thomson Paradox). This paper investigates the occurrence of this paradox when transit authority can have different economic objectives (profit-maximizing or breakeven) and operating schemes (frequency, fare, or both frequency and fare). For various combinations of economic objectives and operating schemes, the interaction between highway expansion and transit service is explored, as well as its impact on travelers' mode choices and travel utilities. Further, for each combination, the conditions for occurrence of the Downs-Thomson Paradox are established. We show that the paradox never occurs when transit authority is profit-maximizing, but it is inevitable when the transit authority is running to maximize travelers' utility while maintaining breakeven. This is because the former transit authority tends to enhance transit service (e.g., raise frequency or reduce fare) when facing an expanded highway; and on the contrary, the latter tends to compromise transit service (e.g., reduce frequency or raise fare). Both analytical and numerical examples are provided to verify the theoretical results.

Original languageEnglish
Pages (from-to)244-263
Number of pages20
JournalTransportation Research Part A: Policy and Practice
Publication statusPublished - 1 Dec 2014
Externally publishedYes


  • Downs-Thomson Paradox
  • Highway capacity expansion
  • Profit-maximization
  • Transit fare
  • Transit service frequency
  • Zero-profit

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Transportation
  • Management Science and Operations Research


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