120 ■ CITIES AND CLIMATE CHANGE
externalities created by mixed use—preventing, for instance, small retail shops
from locating in residential areas—while underestimating the positive exter-
nality of reducing trip length for shopping or even entertainment. Most current
zoning laws should be carefully audited to remove the bias against mixed land
use and against large concentrations of businesses in a few areas.
Th e coordination needed between transport investment and management,
pricing of roads and parking, and land use to manage existing and future trans-
port infrastructure and capacity is diffi cult to achieve in the real world. Urban
problems cannot be solved sector by sector but spatially. Th is is why the auton-
omy of municipal authorities is so important. In some cities, urban transport
is managed by national line agencies (this is the case in Mumbai). However, in
very large cities the urban area covers several autonomous local governments,
making it diffi cult to coordinate land use, transport networks, and pricing
across the many boundaries of a typical metropolitan area.
Th e population of New York City includes less than half of the metropolitan
area population, making coordination and policy consistency diffi cult. Most
of Mumbai’s regulatory decisions and infrastructure investment budget are
decided by the legislature of the state of Maharashtra, not by the municipal
corporation, which may explain the lack of spatial development concepts being
applied to zoning regulations. Singapore, being a city-state, has the advantage
of avoiding the contradictions and cross-purpose policies of a metropolitan
area divided into many local authorities with diverging interests. Th is may
explain in part the extraordinary consistency and continuity in urban develop-
ment policies over a long period that has contributed to create such a successful
city. Th e same could be said of Hong Kong, continuing the tradition of Italian
renaissance city-states such as Venice and Florence.
Although good governance and policy consistency are important in reduc-
ing GHG emissions, in the long run only the pricing of energy based on carbon
content will be able to make a diff erence in urban transport GHG emissions.
Pricing transport as close as possible to the real economic cost of operation and
maintenance is the only way to obtain a balance between transport modes that
refl ects consumer convenience and maintains mobility.
Annex
For each motorized transport mode:
Q = VKmT × E,
VKmT = PKmT/L,
PKmT = 2D × P,