  The effectiveness of fiscal policy to influence vehicle purchases for
emissions reductions in private passenger road transport depends on its ability
to incentivise consumers to make choices oriented towards lower emissions
vehicles. However, car purchase choices are known to be strongly socially
determined, and this sector is highly diverse due to significant socio-economic
differences between consumer groups. Here, we present a comprehensive dataset
and analysis of the structure of the 2012 private passenger vehicle fleet-years
in six major economies across the World (UK, USA, China, India, Japan and
Brazil) in terms of price, engine size and emissions distributions. We argue
that choices and aggregate elasticities of substitution can be predicted using
this data, enabling to evaluate the effectiveness of potential fiscal and
technological change policies on fleet-year emissions reductions. We provide
tools to do so based on the distributive structure of prices and emissions in
segments of a diverse market, both for conventional as well as unconventional
engine technologies. We find that markets differ significantly between nations,
and that correlations between engine sizes, emissions and prices exist strongly
in some markets and not strongly in others. We furthermore find that markets
for unconventional engine technologies have patchy coverages of varying levels.
These findings are interpreted in terms of policy strategy.
