2013) using historical data and multinomial regression analysis finds that an increase in income leads to increased vehicle ownership, which, in turn, increases gasoline consumption. The literature also looks at spatial indicators, such as density, diversity, proximity to infrastructure and services, frequency of public transport and parking. Most of the literature here focuses on the urbanization/public transport nexus and finds a positive link between urbanization and reliance on public transport (Camagni _et al._ , 2002; Limtanakool _et al._ , 2006), although with the caveat that this research is based on findings from advanced economies. A further strand concentrates on journey characteristics including travel motives, distance and time, travel costs and so on. A paper on Spain (Rojo _et al._ , 2012) focusing on inter-city travel, uses discrete choice analysis to suggest that passengers tend to value time the most. Travel cost is also well documented as an important determinant of modal choice (De Witt _et al._ , 2013), with consumers being sensitive to price changes, but the extent to which depending on several factors, including the purpose of the trip etc. (Annema, 2002; Litman, 2004). In addition, socio-psychological factors have also been considered. Some of these (attitudes, lifestyle, experience) are largely a function of income, so the literature suggest a somewhat similar relationship between them and decisions on a modal choice (De Witt _et al._ , 2013). Needless to say, most of this research has been conducted in advanced economies.

A separate strand of the literature has focused on simulating/studying the impact of various policy actions on the modal choice (and in addition on car ownership/gasoline consumption and CO2 emissions). For Jordan, Al-Ghandor _et al._ , (2013) do some projections of gasoline consumption with the current level of subsidies and with an alternative policy scenario of removing fuel/energy subsidies. The findings suggest that with current pricing policies gasoline consumption is expected to rise by 1.8% a year (in line with the increase in per capita income/car ownership). Reduction of energy subsidies could reduce the increase of gasoline consumption to 0.5% a year. A similar study on China (He _et al._ , 2013) also simulates fuel consumption/CO2 emissions in China under various scenarios. A paper on Australia (Stanley _et al._ , 2013) considers various policies that have a direct impact on the modal choice and therefore on greenhouse gas emissions (GHG): (i) reduce urban car kilometers traveled; (ii) increase the share of urban trips performed by walking and cycling; (iii) increase public transport’s mode share of urban motorized trips; (iv) increase urban car occupancy rates; (v) reduce forecast fuel use for road freight; (vi) improve vehicle efficiency. Of all of the factors, the paper suggests that increasing fuel efficiency (along with behavioral changes in buying more fuel efficient cars) could significantly reduce (GHG). The paper also suggests comprehensive congestion charging as a possible way forward. Other studies of advanced economies report mixed findings on the likely efficacy of policy. For example, Small (2012) simulates the impact of various energy policies for passenger motor vehicles in the USA. He finds that the impact of various policies suggested/debated would be modest. His conclusion is that higher fuel taxes seem to be the best policy option as their effects set in quickly and are not counteracted by the ‘‘rebound effect’’. Furthermore, a high fuel tax can be combined effectively with a policy mandating new-vehicle fuel efficiency, providing greater effectiveness at a unit cost comparable to that of the fuel tax alone. The paper (even though it does not include any external costs of driving in the model (accidents, congestion etc.) suggests that a fuel tax discourages vehicle travel. A paper by Rentziou _et al._ (2012) offers similar findings. The wider literature looking at fuel price elasticities unambiguously finds that fuel price increases lead fuel consumption to decline, in the short-term 7