The transport sector of the Global Calculator allows users to determine total transport energy demand and emissions using a number of levers. These alter the distance people travel, the amount of freight being moved across the world, and the type of vehicles being used. In the model, passenger and freight transport are considered as separate sub-sectors, each including all relevant transportation options including non-motorised (walking and cycling) and motorised transport (cars, buses, trains and planes) for passengers, as well as trucks, ships and planes for goods.
For motorised transport, the main technical options are considered, from traditional internal combustion engines, to hybrid, electric and hydrogen fuel cell vehicles. Biomass-powered transport is included in the model, but there is no specific lever allowing users to choose the amount of biomass used in this sector. Please see the section on land, bioenergy and food below for an explanation of how bioenergy is used in the model.
Transport is modelled according to geographical area type. The model splits the world into the following categories:
- three types of urban area (automobile cities, transit cities and booming cities)
- two types of rural area (developed and developing)
- two types of international travel area (slow and fast growth).
Driving transport demand
Key drivers explicitly modelled to estimate transport energy demand and emissions are:
- population growth (which is the same as for the other sectors, and is a separate lever)
- the evolution of transport demand per person and the amount of transported goods
- the share of each mode of transport
- the technical choices for each transport mode in the future.
Other factors are modelled implicitly:
- the structure of the territory and the density of habitat in the various regions of the world
- as well as the geographical spread of economic activity.
GDP growth and the wealth of households is not modelled explicitly in the tool: all levels 1 to 4 are designed to be consistent with GDP projections.
Transport and the economy
Transport is a key facilitator of other economic activity, and so impacts on many other sectors of the economy. Some of these interactions are modelled in the Global Calculator, but some aren't. For example:
- Goods transportation depends on the development of other sectors (for example, buildings and industry). Trajectories for these sectors could therefore influence the transport sector, but this is not explicitly modelled.
- Behavioural or technical changes could have unattractive consequences (for example, transport demand may rise if efficiency improves due to "rebound effects"). These are not taken into account directly but the user can simulate them by making appropriate lever choices.
- Changes in electricity demand in the transport sector will affect emissions, but these are included in the electricity production sectors in the model rather than the transport sector itself. Emissions computed in the transport sector are tank-to-wheel emissions only.