Context: Melbourne is experiencing high population growth, generating high demand for housing. This housing boom has increased house prices and rents, as well as the availability of all types of housing. Subdivision regularly occurs in the outer areas of Melbourne, with numerous developers offering house and land packages. However, after 10 years[when?] of planning policies to encourage medium-density and high-density development in existing areas with greater access to public transport and other services, Melbourne's middle and outer-ring suburbs have seen significant brownfields redevelopment.

Question: What types of surburban development did Melbourne policies promote?

Answer: medium-density and high-density