Inertia and shock effects in public transport: The case of metro line 6 in Santiago using smart card data

Traffic forecasting has traditionally relied solely on characteristics related to services and users. However, recent research has highlighted the importance of considering travellers’ psychological factors in explaining travel behaviour. While previous studies have incorporated the role of habits in travel choice behaviour, only a few have analysed the role of inertia and shock related to major changes in transport networks. This study contributes to previous research by revealing the changes in the behaviour of public transport passengers over time after the inauguration of a new metro line in Santiago, Chile, using large-scale revealed-preference data from automated fare collection systems. It explicitly analysed the consequences of the new metro on passenger behaviour by considering different passenger types, using a heteroskedastic mixed latent class public transport mode choice model incorporating both inertia effects resulting from habitual behaviour and shock effects resulting from a significant change to the public transport network. The results confirmed significant habitual behaviour among passengers, in that metro users tended to stick to using the metro, but bus users tended to switch to other modes. However, after the introduction of the new metro line, a significant shock effect was observed, whereby users had an increased tendency to switch to modes that improved their level of service, and this effect increased slightly in the longer term. The results highlight the importance of incorporating inertia and shock effects into behavioural studies.