The CO2 benefits of smoother maritime logistics stem from the reduced use of auxiliary engines of ships during idle time before cargo handling at berth.

In addition, slow steaming and use of optimal speed at sea reduces emissions. Virtual arrival can provide up to 43% CO2 emissions reduction for tankers if speed is reduced to meet an agreed arrival time. This number strongly depends on ship type, size, voyage characteristics and current port times. A study estimated a fuel saving potential in the range of 7.26 to 19% for tankers. BP estimated that implementation of virtual arrival can reduce GHG emissions on the tanker and bulk carrier sectors by around 5%. Another study found that the potential for increased energy efficiency due to reduced waiting time was at least 2–8%. 

Switching from on-board ship auxiliary engines to shore-side power can result in significant CO2 - and other atmospheric local pollutants such SOx and particulate matters - emissions reductions from vessels at the port. Shore power makes it possible to limit ship emissions at berth to practically zero, provided that the electricity used is from zero-carbon energy sources. 

Fully electric vessels generate almost zero greenhouse gases, provided that electricity is generated carbon-free and lifecycle emissions of vessel technology are kept low.

The public procurement procedure for the maritime connection between Stockholm and Gotland incorporated greenhouse gas emissions. In combination with the 10-year duration of the contract, this facilitated the order of LNG-powered vessels by Rederi Gotland AB that may decrease CO2 emissions by around 20%.

The CO2 effects of green port tariff discounts are currently marginal, because the schemes do not target CO2 emissions, are applied for a small amount of ships and in a restricted number of ports. However, environmentally differentiated port pricing has huge potential, if the spread in port tariffs for dirty and clean ships would be large enough, and if more ports would apply the instrument.

As an example, one of the main global tools for differentiated port pricing is the “Environmental Ship Index” (ESI), developed by the International Association of Ports and Harbors. The ESI rates the air emission performance of ships including a basic estimation of CO2 emissions, accounting for 15% of the total score. Currently around 8,000 ships and 57 ports participate in the mechanism.

Environmental subsidies that aim at making the maritime sector more environmentally friendly do result in CO2 emission reductions, albeit indirectly.  Even though the effect has not been specifically measured, it can be concluded that some of these subsides do display positive results when it comes to CO2 emission reduction.

Various effects could be distinguished. First, higher maritime transport costs (due to carbon pricing) could reduce the demand for maritime transport. Second, higher maritime transport costs could make re-shoring more attractive and lead to shorter maritime transport distances (reduction in average tonne/kilometres per trip). Third, higher prices for high carbon fuels (due to carbon pricing) could increase the attractiveness of low- and zero-carbon energy sources for shipping. Studies show that the first effect is fairly marginal, that the second effect could be significant on some trade routes, but that most of the CO2 emission reductions will likely come from the third effect. An example from the study by Parry et al.: An illustrated carbon tax rising to USUSD 75 per tonne1 of CO2 in 2030 (USD 240 per tonne of bunker fuel), and USD 150 per tonne in 2040, by itself reduces maritime CO2 emissions below business-as-usual (BAU) levels by nearly 15 percent in 2030 and 25 percent in 2040, raises revenues of about USD 75 billion in 2030 and USD 150 billion in 2040, while increasing shipping costs by 0.075 percent of global GDP in 2030.

CO2 reductions depend on the type of BRT system implemented (including its energy efficiency and the standard of vehicle used), the type of trips that are replaced by BRT trips and the effect of the BRT system on other traffic. Potential benefits stem from an enhanced mode share of public transit (in case the use of private motorised vehicles can be reduced thanks to the BRT system) and a related possible reduction of traffic congestion.

For example, in Cali (Colombia), a largescale BRT system is estimated to have reduced CO2 emissions of the bus system by 40-60%. Lima’s BRT is estimated to have reduced total CO2 emissions from the city’s entire public transport system by 3-8%.

CO2 reductions from bike sharing systems come from the replacement of trips formerly made by motorised vehicles. The values differ in the literature, especially on how they are measured.

In general, every car km replaced by bike is equivalent to a reduction of 0.185 kg of CO2. Bike sharing replaces car trips with a different rate in different cities. Bike share users report to have decreased their car use in a range from 0% to almost 50%.

The average reported CO2 reduction has been reported as very small or close to 1%. Some papers report that more than 80% of trips are already non-motorised or public transport users.

The reduction in CO2 due to MaaS is expected to primarily come through mode shift from private car to more sustainable modes of travel. The requirement for MaaS fleets to be low or zero emission could further reduce the emissions associated with a trip.

The UbiGo MaaS trial in Gothenburg (an urban application) found that the net effect reduced environmental effects. Larger trials are needed to determine true effect on the environment and vehicle kilometres.

CO2 reduction (based on pilots) depends on country characteristics and the type/extent of MaaS services offered. In the Nordic countries, assuming 10% choose MaaS for commuting trips, the cumulative potential of the five countries is approximately 1227 ktCO2e/year. This is largely based on urban implementation. So while successful MaaS options can reduce CO2, whether MaaS will be successful in rural areas remains a challenge.

Since rural areas often do not have local trains and sufficient public transport, reducing driven kilometres would result in lower emissions. Kilometres could be reduced by ridesharing, organized hitchhiking and  by opening and combining statutory and other transport organized by the public sector. A pilot in Finnish rural areas  showed that combining rides 

The CO2 reduction potential of modal shift towards inland waterways depends on the distance that will be covered by this mode and the carbon intensity of alternative modes. In the Netherlands, between 2005 and 2014 there was a shift of 2.8% from road transport to inland waterways transport. For freight transported in distances between 300 and 500 km, modal shift allowed decreasing emissions in that particular market by around 80%. For distances between 100 and 300 km, CO2 was reduced by around 43%. The impact will also depend on where the modal shift comes from (from roads and/or from rails), as well as on which vehicle was used before: the Seine-Paris Nord waterway has been linked to a potential modal shift in 25% from road transport, and 75% from rails. In this scenario, road emissions would be mitigated. However, as railways emissions for the corresponding rail segment are lower than those of river transport, emissions could increase by around 12 tCO2eq each year.

The impact of governance arrangements can be hard to assess. European experience shows that creating international agreements on inland waterways regulations and standards is required for harnessing the potential of the mode for intra-European freight. However, the impact of these efforts is difficult to measure. Some measurements can give an idea of the potential impact of other governance arrangements. In France, the Lyon Terminal society was created in 1993 to be able to coordinate the activities between the Marseille port and its hinterland. Most specifically, cooperation was achieved with authorities from the Lyon inland port. This increased cooperation contributed to waterways traffic being quadrupled between 1993 and 2008: traffic went from 32 000 TEU in 1993 to 137 000 TEU in 2008.