Air quality: key behaviours report

5 Switching to a less polluting vehicle

5.1 Evidence on air quality impacts of switching to a less polluting vehicle

Alongside supporting an overall reduction in car use, the review highlighted other transport-related behaviours that have the potential to impact on air quality. The most significant of these relate to vehicle choices. Most interest in the literature centres on the potential benefits of switching from conventional vehicles to electric vehicles (EVs), whether battery electric vehicles (BEVs) or hybrid electric vehicles (HEVs). In this section we focus primarily on switching to EVs, given the considerable potential benefits for air quality, as well as the alignment of this behaviour with Net Zero objectives around decarbonising the transport sector. However, some sources highlight differences between petrol and diesel cars (European Environment Agency, 2018) (which may depend on the age of the car, and vary depending on the type of pollutant of interest) and others focus more on replacing older, less fuel-efficient cars with newer ones (El-Dorghamy, 2014), or on the impacts of smaller versus larger cars (Gillies et al., 2005; Kim, 2007).

Air quality benefits accrue due to the use of EVs compared to combustion engines, due to the absence of exhaust emissions from BEVs (European Environment Agency, 2018). However, EVs are not entirely pollution-free, as particulate matter is still produced by tyres and brake wear of the vehicle (Quarmby et al., 2019). These sources of PM can be considerable. It is reported that in the UK in 2015, more than two-thirds of PM10 emissions were from tyre and brake wear and road abrasion (Quarmby et al., 2019) – although regenerative braking technology helps to reduce the emissions from brake wear in EVs (European Environment Agency, 2018). The extent of the benefits of EVs over conventional vehicles in terms of PM emissions will also depend on driving conditions and vehicle weights, as EVs tend to be heavier than combustion vehicles (European Environment Agency, 2018). Whilst impacts of switching to EVs on PM may be variable, these is clear evidence of considerable benefits in relation to air quality more broadly. Studies modelling the impacts of wide scale switching to EVs, have estimated large reductions in NOx concentrations (Ferrero et al., 2016; Requia et al., 2018; Rizza et al., 2021; Soret et al., 2014) and improvements in air quality indices (Christensen & Salmon, 2021), as well as benefits to human health (Hooftman et al., 2016; Rizza et al., 2021). For example, Ferrero et al (2016) estimated that shifting 50% of light vehicles in Milan to EVs could result in a 14% reduction in NOx. Another study, modelling a 100% shift of light vehicles to EVs in Taiwan could result in an estimated 27% reduction in NOx (Requia et al., 2018). A recent study by Rizza et al. (2021) estimated that, for the city of Turin, Italy, a shift in vehicle fleet away from primarily diesel and petrol vehicles to a 2030 scenario of 20% electric, and 50% hybrid vehicles (with only 4% of cars fuelled by diesel) could result in an 87% reduction in NO2 concentrations.

One of the major factors influencing the extent of the air quality benefits from switching to EVs is the energy mix used in electricity production (EPRI & NRDC, 2015; Hawkins et al., 2012). Where the electricity grid is powered primarily by fossil fuels, while there might be improvements to local air quality around roads, emissions are shifted to power stations (European Environment Agency, 2018; Requia et al., 2018). Whilst coal contributes very little (only 1.5%) to the UK's electricity generation mix, contributions from biomass (5.2%) and gas (38.5%) mean that some of the air quality benefits of switching to EVs will be offset by displaced emissions from electricity generation across the UK (European Environment Agency, 2018; National Grid, 2023). Therefore, the decarbonisation of electricity production is central to the future air quality benefits of the transition of the vehicle fleet to EVs.

On the basis of the evidence reviewed, we propose one key behaviour relating to switching to a less polluting vehicle:

Switching vehicle

Switching to an electric vehicle

5.2 Factors influencing switching to electric vehicles

A range of motivations and barriers to switching to EVs were identified in the literature. These are summarised below in Table 7 in relation to capabilities, opportunities and motivations.

Table 7: Capability, Opportunity and Motivation factors influencing switching to electric vehicles

Switching to electric vehicles (EVs)

Capability

Knowledge about range

"Range anxiety" is a typical concern for potential EV users, as most people either do not have sufficient knowledge on the technological advancement of EVs' actual travel range (Franke et al., 2012; Haddadian et al., 2015), or their related perception is psychologically biased (Bonges & Lusk, 2016; Jensen et al., 2013; Quak et al., 2016). Being able to try out an EV (e.g. through rental or a car club) can help to reduce range anxiety, which may help encourage people to consider purchasing an EV (European Environment Agency, 2018).

Opportunity

Cost

At present, the purchasing price of EVs is considered as the most significant barrier for switching from conventional cars to EVs (Keyvanfar et al., 2018; Krupa et al., 2014; Mock & Yang, 2014). In a Scottish survey, 67% of respondents reported the initial cost as a barrier to switching to an ultra-low emission vehicle (BMG Research, 2023). Reducing the purchasing price by providing subsidies is a route to broader access to affordable EVs (Quarmby et al., 2019).

Charging infrastructure

"Range anxiety" can be related to the lack of charging stations or parking slots devoted to EV (Bonges & Lusk, 2016; Harrison & Thiel, 2017; Mock & Yang, 2014). Concerns about the range of cars in relation to access to charging infrastructure can be a greater barrier for rural residents compared to those living in large urban areas in Scotland (BMG Research, 2023).

Social norms

Current social norms and policies encourage people to switch to EVs (Hawkins et al., 2012; Pielecha et al., 2020). Cherchi (2017) found that, in an experimental environment, high social conformity (many others use the EVs) can largely overcome the financial barrier to encourage people to purchase EVs.

Motivation

Environmental concerns

With the rise in concerns about the environment, people may opt for EVs. Singh et al. (2023) demonstrated that psychological factors such as perceived value, personal norms, etc. can be significant contributors to promote the transition. In a survey of Scottish residents, 31% reported the reduced environmental impact of EVs as a motivator for buying them (BMG Research, 2023).

Fuel and cost saving

EVs are generally considered as advantageous for reducing fuel dependency (Jochem et al., 2016), with financial benefit also an important motivator for using EVs. Lower running costs are the most common perceived incentive for buying an EV, reported by 32% of Scottish respondents (BMG Research, 2023).