Scandinavian Working Papers in Economics

Working papers in Transport Economics,
CTS - Centre for Transport Studies Stockholm (KTH and VTI)

No 2018:3: Quantifying errors in travel time and cost by latent variables

Juan Manuel Lorenzo Varela , Maria Börjesson and Andrew Daly
Additional contact information
Juan Manuel Lorenzo Varela: CTS - Centre for Transport Studies Stockholm (KTH and VTI), Postal: Centrum för Transportstudier (CTS), Teknikringen 10, 100 44 Stockholm, Sweden
Maria Börjesson: CTS - Centre for Transport Studies Stockholm (KTH and VTI), Postal: Centrum för Transportstudier (CTS), Teknikringen 10, 100 44 Stockholm, Sweden
Andrew Daly: ITS, Leeds

Abstract: Travel time and travel cost are key variables for explaining travel behaviour and deriving the value of time. However, a general problem in transport modelling is that these variables are subject to measurement errors in transport network models. In this paper we show how to assess the magnitude of the measurement errors in travel time and travel cost by latent variables, in a large-scale travel demand model. The case study for Stockholm commuters shows that assuming multiplicative measurement errors for travel time and cost result in a better fit than additive ones; however, when measurement errors are modelled, the estimated time and cost parameters are robust to the modelling assumptions. Moreover, our results suggest that measurement errors in our dataset are larger for the travel cost than for the travel time, and that measurement errors are larger in self-reported travel time than software-calculated travel time for car-driver and car-passenger, and of similar magnitude for public transport. Among self-reported travel times, car-passenger has the largest errors, followed by car-driver and public transport, and for the software-calculated times, public transport exhibits larger errors than car. These errors, if not corrected, lead to biases in measures derived from the models, such as elasticity and values of travel time.

Keywords: Hybrid choice models; Latent variables; Error quantification; Measurement error models; RP Value of Time; Self-reported indicators

JEL-codes: R40

27 pages, February 20, 2018

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