## 2 Materials and Methods
### Methodology for the Estimation of Energy Consumption and Emissions  
The factors used in the calculations are taken from the database of average emission factors for road transport in Italy created by ISPRA [47] in accordance with the updated COPERT estimation model version 5.1.1. and the EMEP/EEA Air Pollutant Emission Inventory Guidebook [48]. For the present work, emission factors for the year 2016 were used for the following categories: greenhouse gases: carbon dioxide (CO\({}_{2}\)), methane (CH\({}_{4}\)) and nitrous oxide (N\({}_{2}\)O); macropollutants: carbon monoxide (CO), nitrogen oxides (NO\({}_{\rm x}\)) as the sum of nitrogen monoxide (NO), and nitrogen dioxide (NO\({}_{2}\)), particulate matter (PM), benzene and nonmethane volatile organic compounds (NMVOC); micropollutants: metals, polycyclic aromatic hydrocarbons (PAH) and benzo-pyrene (BaP); and fuel consumption. With regard to particulate emission factors, PM10 and PM2.5 were used. Both estimate both particulate matter from combustion (exhaust), which is almost entirely made up of particles smaller than 2.5 um, and that from tire wear, vehicle brakes and road surface abrasion (nonexhaust). The same was done for the estimation of metals. Emissions of nonmethane volatile organic compounds from petrol vehicles include evaporative emissions in addition to exhaust. COPERT fuel consumption emission factors refer to energy consumption and are expressed in MJ/km. The litres of fuel consumed were calculated by using the density values and calorific value from [48]. The Global Warming Potential Values from the IPCC Fifth Assessment Report, 2014 (AR5) [49] were used to convert methane and nitrous oxide into CO\({}_{2}\) equivalent.  
The equation to calculate the emissions is  
\[Q_{p_{i}}=\sum_{1}^{n}F_{FST}\cdot\mathrm{km}\cdot\mathrm{d}, \tag{1}\]  
where \(Q_{p_{i}}\) represents the emitted quantity of pollutant \(i\), \(n\) is the number of respondents in the sample, \(F_{FST}\) is the pollutant emission factor by fuel, size, abatement technology and type of route (urban, rural, total, mixed), km are the kilometers driven per day, and d are the days worked remotely.  
The described procedure and the specific emission factors [47] are applied to all complete records, which provide all the data requested in Sections 3 and 4 of the questionnaire. In cases in which respondents have omitted some of the required information, equivalent factors are applied according to the following criteria in the absence of specifications on vehicle technology, emission factors referring to the 2016 national average fleet of passenger vehicles by fuel type are used: in the absence of information on engine capacity, the COPERT value for the particular type of fuel used is considered; in cases in which the fuel type is also omitted, emission factors referring to the 2016 national average passenger vehicle fleet are used; in the absence of information on the type of journey, it is considered mixed; in the absence of the specific number of kilometres travelled with the vehicle, the arithmetic average between the extremes of the kilometres travelled was used (data requested in the questionnaire regardless of the means of transport used).