Some programmes attribute awards when a company is able to reduce emissions by 20%. Specific measures like eco-driving can in some cases reduce emissions by 15 to 30%. But there is a great variability on its effects depending on the specific company, environment where it operates and specific measures adopted.

A number of studies quantify CO2 impacts of mode shift to cycling. In a study of Cardiff half of car trips were considered short enough (<5km) to switch to cycling or walking. Taking into account individual travel patterns and constraints (based on the sample), 41% of these could substitute car trips saving nearly 5% of all CO2 emissions from car travel.

In Germany, 11% of trips (3% of total vehicle-kilometres travelled) are by bike, if 50% of all short trips were to switch to bike, this would increase the cycling share to 21% of all trips and reduce car vkms by 3%. This means 39 million vkm, daily, would be replaced which is equivalent to 8 000 tonnes of CO2 daily. Taking into account all the criteria classified by respondents, one third of trips could be replaced, resulting in 11% fewer vkm and therefore a reduction in CO2 emissions of up to 11%.

A study from Ireland finds that shifting from driving to cycling results in 134g CO2e saved per passenger-kilometre.

An e-bike study from Portland (USA) estimates CO2 reductions are in the order of 1 000 metric tons per day if 15% of trips are made by e-bike. This is an approximately 11% reduction considering Portland's current CO2 emissions are approximately 8 000 tons per day. Calculations are based conservatively on the 'dirtiest' electricity generation in USA.

A UK based study using the English National Travel Survey, highlights that encouraging multimodality, which is what cycling infrastructure in non-urban environments is meant to do, may not have an impact on CO2. When comparing similar distance trips, multimodal trips emit lower levels of emissions, however multimodality as a lifestyle change is not associated with lower emissions, because the greater levels of travel activity among these individuals offset the benefits derived from their multimodal choices. A longitudinal study in the UK analysing impacts of walking and cycling infrastructure finds limited evidence that the infrastructure led to CO2 emission reductions.

GHG emission reductions resulting from the use of financial instruments aiming to support the development of decarbonising solutions are essentially related  with the real capacity of these solutions to contribute to the GHG emission reduction objective, including on one hand upstream emissions, on the other considering long term impacts (EVs for instance increase their benefit year by year due to deployment of green electricity, while NG and other fossils have a worsening trend in upstream GHG emission due to the need of tapping harder and harder to extract resources).The GHG emission savings are therefore dependent on the design of the criteria defining the scope of application of the financial instruments.

In the case of green bonds, the taxonomy developed to characterize the green bond market, as well as the reporting and verification requirements needed to certify bonds as green are the key instruments guaranteeing compatibility with GHG emission mitigation objectives.            

The measure stimulates fleet renewal and the use of electric vehicles for inner-city transport, thus causing a reduction in CO2 caused by heavy vehicles. It can incentivise more efficient operations, better use of available capacity, lowering emissions per ton-kilometre.

The measure stimulates fleet renewal and the use of electric vehicles for inner-city transport, thus causing a reduction in CO2 caused by heavy vehicles.

Reductions in trips and vehicle kilometres result in reductions in CO2 emissions. Reductions of between 30% and 70% of vehicle trips in different cities reported in literature.

Evaluating the impact of labelling programs is challenging. This is mainly because the impact of labelling programs on fleet fuel efficiency cannot easily be isolated from related policies, such as vehicle CO2 emission/fuel efficiency standards and vehicle/fuel tax policies that often run in parallel to labelling programs.

An evaluation of the European car labelling Directive concluded that the Directive appears to have the potential to influence consumer choices in a way that eventually reduces overall CO2 to a degree. However, the realisation of this potential depends strongly on the national implementation, including synergies with relevant fiscal measures and the design of the label and the enforcement of the Directive.

Setting CO2 emission standards for different vehicle types (or tightening them where they are already in place) can reduce CO2 emissions from the respective vehicle types and drive the uptake of alternative fuel vehicles. For example, European CO2 standards for cars in the timeframe between 2011 and 2014 were estimated to have reduced CO2 emissions by 138 million tonnes. Proposals for future European CO2 standards were estimated to reduce well-to-wheel CO2 emissions from cars by around 5%-10% (depending on the stringency of the standards) in 2030.

The CO2 impact of vehicle standards depends to a large degree on the stringency of the standards, the compliance rate with the targets, and any potential discrepancy between vehicles’ CO2 efficiency according to test procedures ‘on paper’ and their efficiency in ‘real-world’ driving conditions. Studies for Europe have shown that the discrepancy between test values and real-life values has, on average, increased to around 40% by 2017. This is because test procedures in controlled laboratory environments do not necessarily reflect real-life driving conditions and driver behavior. There is also a certain degree of flexibility in test procedures that may be ‘exploited’, as well as loopholes in the regulation. New test procedures (such as the so-called Worldwide Harmonized Light Vehicles Test Procedure, WLTP), on-road testing of fuel consumption and CO2 emissions under real driving conditions, and not-to-exceed limits for the real-world gap can help reduce the gap between on-paper and real-life CO2 emissions of vehicles.

The CO2 impact of vehicle standards will further depend on whether potential CO2 benefits may be offset by rebound effects (drivers using their vehicles more thanks to fuel cost savings). Preferences for heavier (and hence less efficient) vehicles may also jeopardise the CO2 effects of vehicle standards. This may be especially the case where vehicle standards are defined to be dependent on the mass (weight) of the vehicle (i.e. heavier vehicles are subject to relatively less stringent targets). In this case, standards do not incentivize vehicle manufacturers to reduce the average weight of their vehicles – a measure which could, however, lead to significant further vehicle efficiency improvements.

Studies found that every 10% reduction in vehicle weight can cut fuel consumption and respective CO2 emissions by around 7%.

A study also found that gradually reducing the average vehicle weight of cars from around 1400kg to 1000kg in the European Union, would result in cumulative CO2 savings of around 1200 MT in the period from 2020 to 2050, or in savings of 85MT in year 2050. This is compared to a baseline scenario where vehicle efficiency improvements and the uptake of alternative fuel vehicles are not complemented with specific weight reduction measures. In line with these findings, CO2 emission values for new cars would decrease from 78gCO2/km to 56gCO2/km thanks to the weight reductions.

Bans on diesel and ICE vehicles tend to increase the use of cleaner fuel alternatives and/or generate modal shifts away from private cars and towards public transport, walking and/or biking. All of the these trends will decrease CO2 emissions. Diesel bans will also decrease pollutants such as NO2, NOx, PM2.5, and PM10, which have serious health implications.

However, a diesel-specific ban can cause users to switch to petrol cars.

The enforcement of the ban and type of ban will influence the degree of change in CO2 emissions. A study on Dublin showed that a diesel vehicle ban would reduce CO2 emissions by 371,657 tonnes between 2018 and 2024. In Medellin, there was no significant change in emissions during a restricted circulation ban on ICE vehicles in 2017.

The effects on CO2 emissions are not direct and are difficult to quantify. They mostly come from an improved competitiveness of the rail freight alternative, as opposed to road, air or maritime freight alternatives. This improved competitiveness generates a mode shift to rail freight, which is generating less CO2 emissions as of 2020.

Other CO2 emissions reductions come from the optimisation of the rail freight system management, increasing the average load factors and decreasing the empty trips, and from better traffic management and train control reducing energy consumption. Both are difficult to quantify because they heavily depend on the local conditions of the trip, on the set of technologies developed and implemented, and on interactions between all of these.