 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”.DRT schemes may require new or amended legislation, or special dispensation, to operate, as they do not meet the traditional licensing model of authorised bus transport providers or licensed taxicab operators.The status has caused controversy between bus and taxi operators when the DRT service picks up passengers without pre-booking, due to the licensing issues.