Traffic forecast inaccuracy in transportation: a literature review of roads and railways projects

  • Carlos Oliveira CruzEmail author
  • Joaquim Miranda Sarmento


The inaccuracy of traffic forecasts has long stood as a central research theme in the field of infrastructure and transportation studies. The literature presents several motives for this phenomenon, ranging from a political bias, insufficient technical preparation, changing urban patterns, and economic dynamics. Uncertainty due to the inaccuracy of forecasts can have a profound impact on the infrastructure development process, right through from the preliminary studies up until the operation and re-negotiation of contracts (in cases when projects are developed using a concessions model). This paper provides an extensive systematic review of forecast inaccuracy in roads and railways projects (analyzing trends, causes, and results). The research found that: (1) forecasts in rail projects are generally more optimistic than in road projects; (2) over the last couple of decades the accuracy of forecasts has not improved significantly, and; (3) there has been a generalized ramp-up effect in forecasts.


Traffic forecast Forecast inaccuracy Optimism bias Systematic review Strategic behaviour Roads Railways 

JEL Classification

H54 J68 R41 R42 



Joaquim Miranda Sarmento gratefully acknowledges the financial support received from FCT-Fundação para a Ciência e Tecnologia (Portugal), and also the national funding obtained through a research Grant (UID/SOC/04521/2019).


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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  • Carlos Oliveira Cruz
    • 1
    Email author
  • Joaquim Miranda Sarmento
    • 2
  1. 1.CERIS, Instituto Superior TécnicoUniversidade de LisboaLisbonPortugal
  2. 2.CSG/Advance, ISEG - Lisbon School of Economics and ManagementUniversidade de LisboaLisbonPortugal

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