Investigation into the phenomenon of reduced household travel survey derived trip generation rates in Gauteng Province

Abstract

Gauteng Province has carried out two household travel surveys (HTS) – the first was carried out in 2000 and the recent one was completed in 2014. HTSs are the mainstay of transport planning and modelling, being used by the province to update the Gauteng Provincial Strategic Transport Model, among other things. The household AM peak trip generation rates according to this recent survey are indicated to be lower than that found in the 2000 HTS. A similar trend has been reported in South Africa, albeit with moderate changes. The paper investigates the statistical significance of the lower trip generation rates for the current HTS and further interrogates the results to determine plausible causes for the lower trip generation rates. While factors such as reduced household size, increased unemployment and peak spreading are found to be present, it is the design of the survey instrument resulting in respondent fatigue that is found to be the main cause. In response, the paper provides some recommendations for improved design of survey instruments for cases where whole day travel is being measured.