Measuring willingness to pay for travel time savings, CO2 emissions reduction and calories burned when multiple modes are available: an application of the partial choice set approach

While the value of travel time savings (VTTS) has been extensively studied, and willingness to pay (WTP) for decarbonisation has been explored in contexts such as air travel, vehicle purchases, and energy consumption, their integration within multimodal urban transport choice experiments remains underexplored. This study bridges this gap by incorporating CO2 emissions and calories burned into stated choice experiments (SCEs) using a partial choice set design to manage the complexity of presenting multiple single-mode and multimodal alternatives. An Integrated Choice and Latent Variable (ICLV) model is estimated directly in WTP space, capturing preference heterogeneity across 15 alternatives for long journeys and 8 for short journeys in a car-dependent area of the UK. A latent variable, environmental friendliness (EF), is identified through an Exploratory Factor Analysis and linked to mode choice and WTP for CO2 reductions. Based on weighted data from 1,255 residents in the Solent area, the results show that walking has the highest VTTS among all modes, followed by car and cycling, while public transport (PT) and hired micro-mobility modes have intermediate values, and combined modes have the lowest VTTS. The mean WTP for reducing CO2 emissions is £4.31 per kg with a median of £2.02 per kg, though this varies substantially with individual levels of environmental friendliness. WTP for calories burned while travelling decreases with age: younger travellers appear indifferent to, or mildly value, physical effort, while older travellers prefer to minimise it. These findings provide evidence-based insights for policies promoting sustainable transport modes (hired micro-mobility, active travel, PT, and combined modes) in car-dependent societies, tailored to different attitudinal and demographic segments. The substantial heterogeneity in WTP for CO2 reductions, driven by environmental friendliness, suggests that information-based nudging interventions may be particularly effective for environmentally conscious travellers.