Box 5.1 uses the experience of the United Kingdom in greenhouse gas mitigation policy to illustrate the kinds of institutional reform that may be required in order to facilitate widespread change in relation to a complex and pervasive environmental problem. For example, a strong preference for personal mobility has led some industrial societies to construct good roads, but poor public transport networks. This reinforces dependence on private motor cars, which will in turn make policies intended to reduce that dependence costly or unpopular. Such policy is likely to require the provision of alternative infrastructure to facilitate a mode switch.2 Simply maintaining infrastructure is expensive, drastically changing it can be much more so. It is therefore helpful when policy reform is aligned with cycles of infrastructure renewal, so that the new infrastructure appropriate to the reform can replace the old at the end of its life.