This layout is typically chosen to improve the traction or the handling of existing vehicle designs using the rear-engine, rear-wheel-drive layout (RR). Notable vehicles with the R4 layout include several high-performance Porsche sports cars, including the 959, the 911 Turbo since the introduction of the turbocharged version of the 993 series in 1995, and the 911 Carrera 4 introduced with the 964 series in 1989.