Background Despite the manifest environmental benefits of public transit, the daily or periodic maintenance operations of an urban bus transport fleet in a large city such as Valencia can itself be damaging in terms of the effluents released. For bodywork, the washing water, containing low quantities of oils and fats with low COD (Chemical Oxygen Demand) values - the amount of oxygen in mg/l required to oxidise both organic and oxidisable inorganic compounds)is 125 mg/l. However colour and odour emissions do not permit its reuse. The motor washing water has similar characteristics, as well as solvents. Their emulsified oil content is higher and its COD is around 2,500 mg/l. Glycol refrigeration fluids are filled with radiator and distribution conduit dirt. Their COD is 500,000 mg/l. If cleaning takes place after draining, the COD of radiatorcleaning water is around 10,000 mg/l. Without prior draining, its COD is between 80,000 and 100,000 mg/l. Flat-battery acids contain 15-20% sulphuric acid and dissolved lead in a colloidal state, accumulated during the running down process. Brake fluids have very high COD levels (1,500,000 mg/l). Their degradation is the consequence of an accumulation of substances in suspension, metals and waters. Despite the multifarious above concerns, recycling practices to prolong the life-cycle of the effluents generated are unheard of in the public transport sector. Objectives The project aimed to introduce technologies such as ultrafiltration, microfiltration, vacuum evaporation, and electrolysis, which, despite already being well known and applied in other areas, are unfamiliar in the transport sector. Through the transfer and application of best available technologies (BATs), the project hoped to define a waste management model for the majority of liquid residuals generated in the maintenance and operation of a fleet of public transit vehicles. The management strategy for these residuals was to consist of both a reduction in environmental hazards and an increase of their life-span. This was to take place at the very point of generation, thus minimising the need for external management. Specifically, the project planned to address problems caused by cab washing waters, motor washing waters, waters from rinsing cooling circuits, cooling fluids, brake fluids, and acids from exhausted batteries. Results URBANBAT represents an innovative and pioneering initiative thanks to the reduction of the environmental impact of the transport sector in general and of the public transit sector in particular. The project achieved what was planned in the proposal: to define a waste management model for the majority of liquid residuals generated in the maintenance and operation of vehicles’ urban fleet by reducing environmental hazards and increasing its life span. Nevertheless, the extension of the methodology to other public transit systems will only be possible where public administrations co-finance the investment to introduce such techniques. Regarding water from washing bodywork, almost all the water consumed was reused (13,300 m3/year). Recovery of 87% of the used water produced high-quality water, and recovery of the remaining 11% produced water that could be put to other, less demanding uses. There was 100% recovery of waters with used antifreeze. Of the 230 m3/year of water used in the washing engines and motors, 96% is recoverable. However, all treated water from cleaning cooling circuits and radiators (65 m3/year) is not–recoverable and must be dumped down the drain after conditioning. This project has been selected as one of the "Best" LIFE Environment projects in 2007-2008