According to Environment Canterbury, Christchurch geography and public transport usage patterns mean that public transport is currently best served with a bus-based system. However, in anticipation of future growth they are intending to consider other transport modes with preliminary investigations due in 2008. Other transport modes to be investigated, such as heavy rail or new light rail systems, are expected to meet several performance criteria before they can be considered as options for future public transport requirements. Also suggested has been a hybrid bus/rail system which makes use of the existing heavy rail network around Christchurch to provide services to satellite towns with vehicles that are also able to run off the rails in a guided busway.