at the Nürburgring, Audi finally joined the DTM as a factory entrant in 2004. The three constructors involved decided to switch to D-segment compact executive-based saloon bodies. The road models used as patterns since 2004 are the Audi A4, Opel Vectra GTS and the Mercedes-Benz C-Class. All dimensions, like the wheelbase, are identical in order to provide equal opportunities without the actual design of the road cars having any influence. Audi immediately had success in 2004 with Swedish driver Mattias Ekström, now a long-time veteran of the sport, becoming a DTM series champion for the first time. DTM in 2005–2006 The championship suffered a setback in 2004 when long-time entrant Opel decided to pull out of the series at the end of the 2005 season, as part of a large cost-cutting operation in General Motors European division. Initially, the gap looked set to be filled by MG Rover, however their plans to enter the series were canceled after the company collapsed in April 2005. As a result, Audi and Mercedes ended up fielding 10 cars each in 2006, but the television deal with the major German television station ARD required three marques to participate in 2007 in order to continue the broadcast agreement. DTM in 2007–2013 The DTM carried on with only two manufacturers in spite of the television agreement requiring three manufacturers to participate in the series. The 2007–2009 seasons were marked by the dominance of Audi. Swede Mattias Ekström won the second of his two titles in 2007, and Timo Scheider took the driver's championship in the following two years. Mercedes-Benz were in the runner-up positions in both 2008 and 2009 (Paul di Resta in 2008 and Gary Paffett in 2009). In 2010, Mercedes finally bridged the gap to Audi, as di Resta won the 2010 championship driving for AMG-Mercedes. In 2011 and 2012, the DTM held a Race of Champions-style exhibition event in the Munich Olympic Stadium. In 2012 BMW made a return to the series after a twenty-year absence, and won the drivers, teams, and manufacturers titles. 2012 also marked the return of three-car manufacturers since 2005 season. Audi switched from the A4 to the A5 in 2012 and to the RS5 in 2013. In 2013, the Drag Reduction System identical to the system used in Formula 1 was introduced by ITR to improve racing in DTM. Recent history (2014–present) In 2014, the body shape and