In order to forecast the impacts of car sharing on travel demand, network performances and land use, it is important to understand factors affecting the adoption and the use of this service (Dias et al., 2017). Table 1 shows the main variables that were found to significantly affect the user’s choice to join a car sharing program and the usage frequency of car sharing. Factors were aggregated in the following groups: socio-economic variables both at individual and household level, characteristics of a specific trip under analysis, travel habits and personal awareness of potential adopter. Effects of each variable were classified as: positive, negative or specific, i.e. the impact of a variable was estimated only for a particular class of that variable. Furthermore, the “unspecified” category includes works where a factor was considered, but the related effect was not explained, sometimes because it was introduced in wide models, such as Agent-Based models (Ciari et al., 2015). Observing this table, one can note that opposite effects are often reported for the same variables, by different authors (Ceccato and Diana, 2018). This might be due to the adopted analysis technique (Efthymiou and Antoniou, 2016) or since factors are site-specific. Moreover, it suggests that results cannot be easily generalized to study areas which are different from the analysed one.
Table 1 shows that car sharing users tend to be young (Becker et al., 2017a), in particular 25-35 years old (Shaheen and Martin, 2010), with high educational level (Clewlow, 2016). Moreover, car sharing seems to be adopted by both men and women, even if there is still a great attractiveness for potential female users (Alonso-Almeida, 2019). Future car sharing adopters are also full-time employed (Dias et al., 2017) or students (Le Vine et al., 2014a), owing a driving license (Sioui et al., 2012) and a public transport subscription (Kopp et al., 2015). Furthermore, users tend to live in dense urban areas (Kopp et al., 2015), where there is a high public transport Level Of Service (Becker et al., 2017b). In addition, car sharing adopters live in households with high income (Efthymiou and
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Antoniou, 2016) and few owned cars (Martin et al., 2010). Other variables confirmed that the private car has a negative effect on car sharing adoption, such as the ratio between the number of members and cars in the household (de Luca and Di Pace, 2015), the frequency of use of private cars (Nobis, 2006), the presence of private car park near home (Ceccato and Diana, 2018) and the symbolic value of car (Kim et al., 2017b). Furthermore car sharing adopters tend to frequently use sustainable modes, such as public transport (Kim et al., 2017a) and non-motorized modes (Efthymiou et al., 2013), indeed environmental awareness is often observed among users (Millard-Ball et al., 2005) and electric shared vehicles are preferred (Zoepf and Keith, 2016). Finally, diffusion of technology seems to have a positive effect on the car sharing adoption (Shaheen and Martin, 2010).
On the other hand, several authors analysed the propensity to use car sharing focusing on a particular trip, therefore also trip-specific variables were included in Table 1. As expected, car sharing in-vehicle travel time, distance, cost (Becker et al., 2017b), and walking time to reach the nearest available vehicle (Zhou and Kockelman, 2011) have a negative effect on the choice. Furthermore, the majority of authors reported that car sharing is mostly used for discretionary trips (Kim et al., 2015).
Some authors analysed the variables affecting the choice to use car sharing by distinguishing various service models (Ciari et al., 2015). In this way, the effect of considered factors is different.
For instance, Becker et al. (Becker et al., 2017a) compared characteristics of user groups of both Round-trip and One-way car sharing services. Furthermore, the propensity to use these two services was estimated also by Yoon et al. (Yoon et al., 2017) using Stated-preferences experiments.
Moreover, after the increasing of environmental awareness and sustainability targets, several authors focused on the adoption of shared electric vehicles (Burghard and Dütschke, 2019; Cartenì et al., 2016).
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Table 1. Variables affecting the use of car sharing: results from previous researches
Variables Effect Authors
Socio-economic - Individual level
Age Negative (Alonso-Almeida, 2019; Becker et al., 2017a;
Burghard and Dütschke, 2019; Ceccato and Diana, 2018; Coll et al., 2014; Dias et al., 2017; Martin and Shaheen, 2011a; Millard-Ball et al., 2005;
Nobis, 2006; Paundra et al., 2017; Rotaris and Danielis, 2018; Vinayak et al., 2018; Wang et al., 2012)
Positive (Carroll et al., 2017; Cervero et al., 2007; de Luca and Di Pace, 2015; Kim et al., 2015)
FF: (Yoon et al., 2017)
Unspecified (Acheampong and Siiba, 2019; Ciari et al., 2015, 2014; Cooper et al., 2000);
Specific +[26-35]: (Efthymiou, 2014; Efthymiou and Antoniou, 2016)
Juschten et al., 2017; Kim et al., 2017a; Morency et al., 2012; Perboli et al., 2017; Shaheen et al., 2018; Yoon et al., 2017)
Female (Burghard and Dütschke, 2019; Cervero, 2003;
Cervero and Tsai, 2004; Coll et al., 2014; de Luca and Di Pace, 2015; Heilig et al., 2017; Kim et al., 2015; Martin and Shaheen, 2011a; Millard-Ball et al., 2005; Nobis, 2006; Vinayak et al., 2018;
Zheng et al., 2009)
Unspecified (Alonso-Almeida, 2019; Ciari et al., 2015, 2014;
Paundra et al., 2017)
Married Positive (Efthymiou, 2014; Efthymiou and Antoniou, 2016)
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Educational level Positive (Becker et al., 2017a; Burghard and Dütschke, 2019; Carroll et al., 2017; Celsor and Millard-Ball, 2007; Ciari and Axhausen, 2012; Clewlow, 2016;
Coll et al., 2014; Cooper et al., 2000; Dias et al., 2017; Juschten et al., 2017; Kim et al., 2017a;
Kopp et al., 2015; Lane, 2005; Martin and Shaheen, 2011a; Millard-Ball et al., 2005; Nobis, 2006; Shaheen et al., 2018; Shaheen and Martin, 2010; Vinayak et al., 2018; Wang et al., 2012) Negative (Acheampong and Siiba, 2019; Wagner et al.,
2016, 2015)
Unspecified (Ciari et al., 2015, 2014)
Employment status Positive (Becker et al., 2017a; Carroll et al., 2017; Cartenì et al., 2016; Dias et al., 2017; Kim et al., 2015;
Sioui et al., 2012; Vinayak et al., 2018) Negative (Nobis, 2006)
Unspecified (Ciari et al., 2015, 2014)
Specific +[Student]: (Le Vine et al., 2014a; Perboli et al., 2017; Rotaris and Danielis, 2018; Zheng et al., 2009)
-[Student]: (Zhou and Kockelman, 2011) +[Unemployed]: (Rotaris and Danielis, 2018) Driving licence Positive (Acheampong and Siiba, 2019; Dias et al., 2017;
Morsche et al., 2019; Rotaris and Danielis, 2018;
Sioui et al., 2012; Winter et al., 2017; Yoon et al., 2017)
Negative (Carroll et al., 2017)
Public transport subscription Positive (Becker et al., 2017a; Ceccato and Diana, 2018;
Cooper et al., 2000; Heilig et al., 2017; Juschten et al., 2017; Kopp et al., 2015; Yoon et al., 2017)
Juschten et al., 2017; Kim et al., 2017a; Kopp et al., 2015; Lane, 2005; Martin and Shaheen, 2011a;
Millard-Ball et al., 2005; Nobis, 2006; Shaheen and Martin, 2010; Vinayak et al., 2018)
FF: (Yoon et al., 2017)
Negative (Cervero et al., 2007; Ciari and Axhausen, 2012;
Coll et al., 2014; Dias et al., 2017; Kim et al., 2015; Kortum and Machemehl, 2012; Wagner et al., 2016, 2015; Wang et al., 2012; Zhou and Kockelman, 2011)
RT: (Yoon et al., 2017)
Unspecified (Efthymiou, 2014; Efthymiou and Antoniou, 2016)
Household size Positive (Burghard and Dütschke, 2019; Ciari and Axhausen, 2012)
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Negative (Ceccato and Diana, 2018; Celsor and Millard-Ball, 2007; Cooper et al., 2000; Kim et al., 2017a;
Kortum and Machemehl, 2012; Lane, 2005;
Millard-Ball et al., 2005) Unspecified (Ciari et al., 2015, 2014) Specific +[Single]: (Kim et al., 2017b)
+[2]: (Sioui et al., 2012), (Efthymiou et al., 2013) +[4 members]: (Perboli et al., 2017)
Number of children Positive (Carroll et al., 2017; Coll et al., 2014; Rotaris and Danielis, 2018; Sioui et al., 2012)
Negative (Dias et al., 2017; Kim et al., 2017a; Namazu et al., 2018; Vinayak et al., 2018)
Number of workers Positive (Ceccato and Diana, 2018; Namazu et al., 2018) Negative -
Number of owned cars Positive (Paundra et al., 2017) RT: (Yoon et al., 2017)
Negative (Acheampong and Siiba, 2019; Becker et al., 2017a; Burghard and Dütschke, 2019; Catalano et al., 2008; Ceccato and Diana, 2018; Celsor and Millard-Ball, 2007; Clewlow, 2016; Cooper et al., 2000; Dias et al., 2017; Juschten et al., 2017; Kopp et al., 2015; Lane, 2005; Martin and Shaheen,
Specific +[1]: (Efthymiou, 2014; Efthymiou and Antoniou, 2016)
+[2]: (Perboli et al., 2017)
Number of owned bicycles Positive (Becker et al., 2017a; Coll et al., 2014; Juschten et al., 2017)
Negative (Cervero et al., 2007) Number of owned motorbikes Positive (Ceccato and Diana, 2018)
Negative -
Drivers/car Positive (Coll et al., 2014; Juschten et al., 2017) Negative (Rotaris and Danielis, 2018)
Household members/car Positive (de Luca and Di Pace, 2015; Heilig et al., 2017) Negative -
Private parking near home Positive -
Negative (Ceccato and Diana, 2018; Juschten et al., 2017;
Martínez et al., 2017)
Working location Unspecified (Carroll et al., 2017; Ciari et al., 2015, 2014) +[Near home]: (Martin and Shaheen, 2011a) -[Out of home]: (Kortum and Machemehl, 2012) Trip characteristics
Car sharing cost Positive (Carroll et al., 2017; Paundra et al., 2017)
Negative (Becker et al., 2017b; Cartenì et al., 2016;
Catalano et al., 2008; Ciari and Axhausen, 2012;
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de Luca and Di Pace, 2015; Kim et al., 2017a; Le Vine et al., 2014b, 2014a; Martínez et al., 2017;
Millard-Ball et al., 2005; Morsche et al., 2019;
Rotaris et al., 2019; Winter et al., 2017; Yoon et al., 2017; Zheng et al., 2009; Zoepf and Keith, 2016)
Unspecified (Ciari et al., 2015, 2014) Car sharing travel time Positive (Carroll et al., 2017)
Negative (Becker et al., 2017b; Cartenì et al., 2016;
Catalano et al., 2008; Cervero et al., 2007; Ciari and Axhausen, 2012; de Luca and Di Pace, 2015;
Efthymiou, 2014; Efthymiou and Antoniou, 2016;
Kim et al., 2017a; Le Vine et al., 2014b; Martínez et al., 2017; Morsche et al., 2019; Wagner et al., 2016, 2015)
Unspecified (Ciari et al., 2015, 2014) Car sharing walking time Positive (Winter et al., 2017)
RT: (Yoon et al., 2017)
Negative (Ciari and Axhausen, 2012; de Luca and Di Pace, 2015; Kim et al., 2017a; Le Vine et al., 2014a;
Martínez et al., 2017; Rotaris et al., 2019; Zheng et al., 2009; Zhou and Kockelman, 2011)
Specific +[More than 25 km]: (Rotaris and Danielis, 2018) Car sharing walking distance Specific -[Less than 1 km, SB]: (Heilig et al., 2017)
+[Less than 1 km, FF]: (Heilig et al., 2017) Parking cost Positive (Juschten et al., 2017)
Negative (Ciari and Axhausen, 2012; Paundra et al., 2017) Trip purpose Specific +[Leisure]: (Ciari and Axhausen, 2012; Kim et al.,
2015; Millard-Ball et al., 2005) Weather conditions Specific +[Cold and Rainy]: (Becker et al., 2017b)
+[Good]: (Winter et al., 2017)
Departure time Specific +[Morning peak period, RT]: (Yoon et al., 2017) Electric vehicle Positive (Cartenì et al., 2016; Rotaris et al., 2019; Zoepf 2012; Kopp et al., 2015; Kortum and Machemehl,
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2012; Morency et al., 2012; Morsche et al., 2019;
Namazu et al., 2018; Rotaris and Danielis, 2018;
Vinayak et al., 2018; Wagner et al., 2016; Wang et al., 2012; Yoon et al., 2017; Zhou and Kockelman, 2011)
Travel habits
Frequency of car Positive (de Luca and Di Pace, 2015; Kim et al., 2017a) Negative (Kopp et al., 2015; Millard-Ball et al., 2005;
Nobis, 2006; Paundra et al., 2017; Shaheen and Martin, 2010; Sioui et al., 2012)
Frequency of public transport Positive (Celsor and Millard-Ball, 2007; Clewlow, 2016;
Cooper et al., 2000; Kim et al., 2017a; Lane, 2005;
Murphy, 2016; Shaheen and Martin, 2010) Negative (Coll et al., 2014; Nobis, 2006)
Frequency of non-motorized
modes Positive (Celsor and Millard-Ball, 2007; Clewlow, 2016;
Coll et al., 2014; Cooper et al., 2000; Efthymiou et al., 2013; Kopp et al., 2015; Lane, 2005; Shaheen and Martin, 2010)
Negative (Sioui et al., 2012) Personal awareness and habits
Smartphone Positive (Acheampong and Siiba, 2019; Dias et al., 2017;
Shaheen and Martin, 2010; Vinayak et al., 2018) Negative -
Environmental awareness Positive (Acheampong and Siiba, 2019; Efthymiou, 2014;
Efthymiou et al., 2013; Efthymiou and Antoniou, 2016; Millard-Ball et al., 2005; Rotaris and Danielis, 2018; Winter et al., 2017; Zheng et al., 2009)
Negative (Kim et al., 2017b) Symbolic value of car Positive (Nobis, 2006)
Negative (Kim et al., 2017b; Zheng et al., 2009)
Notes: + and – indicate a positive and negative effect, respectively. FF: Free-floating, RT: Round-trip
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