The available literature shows that behavioural responses to P&R facilities are more complex than a simple interception and shortening of car trips. In response to the introduction of P&R facilities, previous car-only users may now decide to use PT for a part of their trip into the city centre; on the other hand, previous PT-only users may now decide to use their private car for a part of the trip, i.e. to get to the P&R facilities.

Overall, the introduction of P&R facilities therefore does not necessarily result in CO2 benefits, especially if the P&R facility is connected to a road-based public transport system. For a rail-based P&R facility in The Hague, NL, a CO2 benefit could be identified. The success of the scheme was attributed to the fact that the P&R facilities were relatively far outside the city-centre, thereby intercepting city commuters early and replacing a large portion of their travel by the rail-based PT system.            

Land-use planning can have significant impact on transport demand in cities. In general, higher density areas, with a greater mix of uses and a street network design that favors alternative transport modes reduce transport demand and related CO2 emissions.

Doubling the residential density across a metropolitan area can lower households' transport demand by about 5 to 12%. If coupled with high employment concentrations, mixed, uses, and other supportive demand management measures, transport demand can be decreased by up to 25%. In the US, it was found that a 1% increase in population density leads to a 0.213% reduction in vehicle kilometres travelled.

The evidence in the literature on the impacts of HCVs has been mixed, in large part due to the varying assumptions on road freight price elasticity and the specific payloads, distances, and costs considered. Assessments of the realised impacts of HCV introduction are largely positive. In Canada, Sweden, and Australia, for example, the introduction of HCVs has been associated with reduced road traffic and CO2 emissions. The overall impacts of HCV introduction will depend on a number of factors, such as the adoption rate, geography of the region, operational patterns of the operators using HCVs, type and density of the cargo being transported, and the extent of existing networks of competing transport modes.

Studies indicate that capacity increases beyond 60 tonnes and 25.25 metres are likely to yield additional environmental benefits. In one study, simulations indicate that further increasing the weight and length restrictions on road freight vehicles in Sweden from 64 tonnes and 25.25 metres to 74 tonnes and 34 metres would decrease CO2 emissions by up to 12.17 mega-tonnes between 2018 and 2058. In Finland, the impact of introducing increased weight and height limits of up 76 tonnes and 4.4 metres for road freight vehicles (up from 60 tonnes and 4.2 metres), is estimated to have led to a reduction of 65,000 tonnes of CO2 emissions in 2015.

Unfortunately, reducing the harmful emissions from diesel fuel combustion is technologically difficult and in the foreseeable future no further reduction of local emissions from diesel vehicles class is expected. In the long term, technologies that do not use hydrocarbon fuels are vastly more promising in tackling local pollution and greenhouse gas emissions.

ERS bear emission reduction potential because vehicles charged via ERS do not cause any tailpipe emissions on the ERS-equipped road stretch. Tailpipe emissions reductions will depend on the degree of electrification of the HDV, its overall energy efficiency and its usage on non-ERS equipped road stretches. In case of pollutant emissions and noise, the impact of potential reductions will vary with the proximity of the road stretch to urban areas or residential zones. In case of CO2 emissions, actual economy-wide reductions depend on the carbon intensity of the electricity that is used to power the vehicle. Studies have shown that ERS bear the greatest CO2 reduction potential compared to all other mitigation options for road freight transport.

Similar to other solutions to electrifying the transport system, ERS drive electricity demand for transport. ERS will only be beneficial in terms of the overall carbon impact of the transport system if the build-up of such systems goes in hand with a decarbonisation of the electricity system. In terms of the impact of ERS on the electricity grid, ERS is expected to be less demanding than more conventional battery vehicles. This is because the continuous electricity supply via the ERS allows for smoother load profiles on the electricity network.

ERS can also impact mode shares. Where ERS allow for significant cost reductions of road freight transport, it may become a more cost effective solution for transport operators than rail transport.

Combined with other measures (e.g. pedestrianized streets, improvement of public transport) it can lead to significant modal shifts towards PT. For example, integrated transport plan that incorporated access restrictions, PT enhancement and parking policies saw PT modal share increase from 11 to 30% in Strasbourg over a period of ten years, similarly PT mode share in Oxford increased from 27% to 44% after the role out of such a strategy. Local pollutants can decrease up to 25% for PM and 75% for carbon monoxide in some locations, values for the overall city centre can be reduced by 30% for nitrogen dioxides and 15% for PMs and carbon monoxide.

Parking regulation packages can lead to a decrease in overall traffic (5.5% Salzburg). Increase in vehicle occupancy (share of single occupancy vehicle dropped from 44 to 32% Munich), reduced vkm from searching for place to park (10 to 3.3 milion passenger car vkm in Vienna), foster the use of public transport (25% reorientation of visitors to public transport in Vienna), reduce car modal share (Helsinki metropolitan area study found that an increase in parking costs by 30% leads to a decrease of car share of 8-10%, while doubling parking costs could lead to a 21% decrease of car share. If parking costs would always be at the same level as the fares of public transport, car share would decrease by 8%.).

On average, cycling or walking saves 747g CO2 per trip if the alternative would have been to take a private car (assuming an average trip distance of 5km).

CO2 benefits of an information campaign (thanks to a potential reduction in car use) may be brought in relation to the funds that are spent on the campaign. The following cases could be identified:

• EUR 60c per person in the target group: around 0.65% reduction in car use

• EUR 160 per person in the target group: around 14% reduction in car use

• EUR 2 300 per person in the target group: around 44% reduction in car use

The potential of mode shift thanks to campaigns depends on the availability/performance of the PT systems in place.

The CO2 effect varies depending on the promoted vehicle fuel type and is rarely directly evaluated.

Low emission vehicles provide direct emissions reduction which can be assessed by the difference in average emissions per kilometre.

For the alternative fuel vehicles case, the CO2 emission effect is a total reduction of the local CO2 emissions, associated with increased electricity consumption. This amounts to shifting the vehicle emission issue to the energy production level. Depending on the energy mix used to produce electricity, the overall CO2 effect may be negative in the case of heavy emissions related to the electricity production, or positive when the energy mix is green.

Impacts of target setting is difficult to measure.

Setting standards is a requirement for deploying charging infrastructure in one given territory. CO2 benefits initially come from those linked to simply allowing infrastructure to exist.

Increasing levels of standardisation can potentially yield higher GHG reduction benefits. Currently in the US, users face access barriers and are not able to use the less than 20 000 stations publically available in the country. Standardisation is essential for allowing users to make use of all existing charging infrastructure. A higher charging infrastructure use rate could point out to an increase of potential GHG emissions reductions.

The CO2 impacts from this measure will come from the consequent penetration of electric vehicles into the fleet, and are subject to the actual capacity of electric vehicles to deliver net GHG emission savings (when compared with alternative technologies) on a life cycle basis, including the need to install a home charger and a portion of publicly available ones.