as quickly as possible to improve the patient's chance of survival, saving lives which may have been lost without the additional resources being available to the ambulance service. Importantly, the deployment of any voluntary responder will not replace the automatic allocation of a regular front line ambulance. There are two principal roles for volunteers within the London Ambulance Service. These roles include: Emergency responder - clinically trained volunteers who operate in marked response cars with blue lights and wear full service uniform, typically working double-crewed and doing shifts of up to ten hours day and night. These come from public-sector backgrounds, including policing. Community responder - defibrillator trained St John Ambulance volunteers attending on call from their homes and responding to 999 calls in their own car without blue lights alongside ambulances. LAS volunteers are supported by London Ambulance Service Voluntary Responder Group, providing logistical and financial assistance to keep volunteers operational. LAS can also call upon auxiliary aid from external voluntary organisations such as St John Ambulance and the British Red Cross, as demonstrated in the 7 July 2005 London bombings. LAS also utilises the GoodSAM app to alert off duty trained medical persons to a nearby cardiac arrest and the location of nearby automated external defibrillators. Fleet The LAS operates around 450 emergency ambulances. In addition it can deploy around 100 fast response units in various cars, motorcycles, or bicycles. Although not a part of the LAS, London's Air Ambulance Charity is deployed by the LAS from its base at the Royal London Hospital in Whitechapel using either its ground RRVs or its helicopter. As well as accidents and emergencies, the LAS operates a 195-vehicle patient transport service (PTS). Previously a centrally funded service, this element of the LAS is now subject to an open market and is required to tender for work from primary care trusts (PCTs) and other NHS bodies. As well as being contracted by a number of London hospitals and PCTs to take patients to and from their pre-arranged hospital or clinic appointments, the PTS responds to ad hoc journey requests and provides specialist transfer facilities. Mercedes-Benz Sprinters are used as frontline A&E ambulances, while Volkswagen Tiguans and Skoda Octavias cars are all used as Fast Response Units (FRU). Motorcycle responders are equipped with the BMW R1200RT. Cycle responders, who operate in areas such as the City of London, the West End, Stratford, Kingston