 Other schemes may be partially or fully self-funded as community centred not for profit social enterprises (such as a Community interest company in the UK).They may also be provided by private companies for commercial reasons; some conventional bus operating companies have set up DRT-style airport bus services, which compete with larger private hire airport shuttle companies.For a model of a hypothetical large-scale demand-responsive public transport system for the Helsinki metropolitan area, simulation results published in 2005 demonstrated that “in an urban area with one million inhabitants, trip aggregation could reduce the health, environmental, and other detrimental impacts of car traffic typically by 50–70%, and if implemented could attract about half of the car passengers, and within a broad operational range would require no public subsidies”.