The Williams FW16 is a Formula One car designed by Adrian Newey for the British Williams team. The FW16 competed in the 1994 Formula One season, with Williams winning the Constructor's Championship, and British driver Damon Hill finishing runner-up in the Drivers' Championship. It is notable as the last car to be driven by three-time world champion Ayrton Senna before his fatal accident during the 1994 San Marino Grand Prix. Its engine was a Renault RS6 3.5 V10. The team's main sponsor was Rothmans, replacing Camel Cigarettes and Canon used on the FW14 and FW15C. The car was designed around the major regulation changes that the FIA had introduced in the off-season, banning the various electronic devices that had been used by the front running cars during the preceding two seasons. The FW16 was a passive evolution of the FW15C that had preceded it. It featured revised bodywork, including a low profile engine cover; taller sidepods; enclosed driveshaft; and an anhedral rear wing lower element, which was previously hinted at on the FW15C. In addition to these changes, the FW16 featured an innovative rear suspension wishbone design, an improved version of the Renault Sport Formula One engine (RS6), and a fuel valve to enable the ability for mid-race refuelling (a rule reintroduced for 1994). As with the previous season, the number 0 car was driven by Damon Hill for the entire year. Only the defending champion had the right to use number 1 and reigning champion Alain Prost had left the sport. The number 2 car was driven by Ayrton Senna. Williams test driver David Coulthard filled in for most of the season but Williams also brought back Nigel Mansell, who had won them the drivers' title for them in 1992, when his Indycar commitments allowed. Although it was fast, the car proved to be a tricky proposition in early testing and in the early part of the season. The car had a number of problems that were not properly remedied: a design flaw was discovered in the car's frontal section and there were attempts to correct this in time for the ill-fated third race, at the San Marino Grand Prix. Various other alterations were made by Newey and Patrick Head to alleviate the car's handling problems, such as the addition of bargeboards at the Spanish Grand Prix; the FIA-mandated modifications to the airbox at the Canadian Grand Prix; and