To meet internationally agreed climate protection targets, a drastic reduction of passenger transport greenhouse gas (GHG) emissions is required. The “Avoid-Shift-Improve”-Approach suggests to meet future transport demand by avoiding unnecessary travel, shifting travel to more environmentally-friendly transport modes and improving the environmental performance of transport modes. Digital applications can contribute to both an increase or a decrease of passenger transport GHG emissions, e.g. by avoiding travel, increasing travel or shifting travel to more GHG-intensive or GHG-efficient transport modes. In view of the large number of digital applications in passenger transport and their uncertain impacts on GHG emissions, the aim of this report is to present a review of (1) digital technologies that are used in passenger transport, (2) applications that are supported by digital technologies and (3) their potential impacts on GHG emissions.

We identified nine central categories of digital technologies that shape passenger transport, namely (mobile) end user devices and apps, telecommunication networks, cloud computing, artificial intelligence and big data, geospatial technologies, digital sensors, computer graphics, automation and robotics and blockchain. These technologies support various applications in passenger transport which can be categorized into digital traveler information systems (e.g. trip planning and booking apps), digital shared mobility services (e.g. car or ride sharing), digitally-enabled transport modes that would not exist without digital technologies (e.g. virtual mobility, taxi drones), digital in-vehicle applications (e.g. automated driving), and digital applications for traffic and infrastructure management (e.g. traffic simulations and mobility pricing).

All described applications can have reducing and increasing effects on GHG emissions. Main levers to reduce GHG emissions are (1) a reduction of number of vehicles produced (e.g. through vehicle sharing), (2) a reduction of total travel distances (e.g. through virtual mobility), (3) an increase in the attractiveness of and shift to more GHG-efficient transport modes (e.g. through multimodal mobility platforms), (4) an increase in the utilization of transport modes and a reduction of vehicle kilometers traveled (e.g. through ride sharing), and (5) an increase in the fuel efficiency of vehicles (e.g. through automated driving systems).

In a real-life setting, the impacts of digital applications depend on the interplay between the applications and their design, existing travel patterns and the policy framework in place. In order put digital applications in passenger transport at the service of climate protection, applications and policies have to be aligned in a way that they promote GHG reducing levers. Otherwise, there is a risk that these applications lead to an increase in GHG emissions, e.g. by inducing additional travel or promoting more GHG-intensive transport modes.

Future research should empirically assess the impacts of digital applications on passenger transport and identify the conditions under which decarbonization potentials will materialize. This will support policy makers and market actors to jointly create conditions under which offering digital applications in passenger transport contributes to a net GHG emission reduction and is economically-feasible.