Ground-based travel to European academic events as an alternative to air travel: Estimating associated greenhouse gas emissions, time and cost.

Objectives: We aimed to identify the number of participants at three differently situated scientific events in Europe realistically able to switch from aviation to ground-based travel, modelling the potential impact of doing so in terms of travel-related greenhouse gas emissions (GHGe), time and costs. Study design: Modelling study. Methods: Travel for participants (N = 137) attending three academic European events in 2025, two centrally, and one peripherally located, was simulated, estimating the associated GHGe, time and cost. Alternative travel scenarios (air- and ground-based), in which participants realistically switched to ground-based travel, were modelled, highlighting differences in travel-related GHGe, time and costs. Results: For this cohort, a central European location gave around 50 % of participants the opportunity to take ground-based travel, reducing total travel GHGe by a maximum of 29 % (14,116 kg of CO2e). While ground-based journeys took longer, cost differences depended on the availability of international ground-based connections and low-cost airlines. Conclusions: The potential to minimise travel-related, event-driven GHGe is driven by the distance from the participants' departing cities to arrival venue, and the number of participants who live within 1000 kms and/or one day's travel time by ground-based means. The ability to realise these GHGe reductions will depend on the extent to which eligible event participants may choose to shift from aviation to ground-based alternatives, driven by their capabilities to navigate such journeys (that may be more complex), and their motivation, which might be enhanced through financial incentives where ground-based transportation is more expensive.