Reducing emissions from transportation is mostly a matter of reducing demand for transported goods, improving fuel efficiency and improving transportation efficiency – that is, moving the same amount of cargo (e.g., people and things) with fewer trips and fewer vehicles. We’re going to start with freight transportation. This includes shipping, rail, and road transport. Important parameters determining the exact value of the emission factor for each mode of transport include:

- The load factor (payload) i.e. CO2 emissions per transport unit. - The energy efficiency of the vehicle, train or vessel. - The carbon intensity of the energy source i.e. the amount of CO2 emitted per unit of energy consumed.

As a rule, transport by water is the most energy efficient mode of freight transport, followed by rail, then big rigs, then smaller vehicles.

Here are some recommendations to reduce CO2 emissions in freight transport:

1. Switch from road to rail transport when possible. 2. Switch from overland to water transport (e.g., ferries, barges and ships) when possible. 3. Manufacturers share deliveries to minimize transport distance to customers, e.g., manufacturers near each other share deliveries to customers near each other. The idea here is to minimize empty cargo space and maximize load factors. 4. Maximize direct deliveries from manufacturer to end user, minimizing transport to and from intermediaries in the supply chain. 5. Minimize empty running (trucks with no load) by better efficiency/logistics and shared use of fleets. You don’t want trucks going hundreds or thousands of miles and then making return trips with nothing. 6. Increase vehicle payloads. The more units of cargo a truck transports, the less CO2 emissions per unit.

That last recommendation means bigger trucks emit less CO2 per unit than smaller ones, other stuff being relatively equal. Sure, big trucks are less fuel efficient per mile – but that’s much less important than fuel efficiency per unit transported. This also means that local is not always better if local means more small trucks and more deliveries per truck (with smaller and smaller loads)and  a lot of empty running on the way home.