Green Infrastructure: Priorities here include investment in infrastructure for urban
public transport systems, investment in inter-urban rail, investment in alternative vehicle
technologies, and investment in the infrastructure for alternative fuelled vehicles (Section 5.1).
One key difficulty here is that when urban public transport schemes are evaluated with cost
benefit analysis, they give lower rates of return than those for road investment. It is only when
the social and environmental costs are explicitly included in the evaluation that these schemes
become more attractive, but these additional costs and benefits are not ones that the private
sector can obtain a financial return on. Yet it is widely acknowledged that if transport is going
to substantially contribute to reductions in energy use and carbon emissions, then the transport
system needs to be based on an efficient urban public transport network, and there are many
options and combinations of strategies that can be used (Table 2). The difficulty here is in
providing evaluation methods that can estimate the full social and environmental costs and
benefits, as conventionally seen for public investment projects (extended cost benefit
analysis), but at the same time being able to present a clear financial analysis that makes the
investment attractive to the private sector. Evaluating projects for fitness of purpose for PPP
contracts may be helpful as this process may help elucidate what investments are most
appropriate for the private sector to fund, and what needs to be a government responsibility.