Testing is not mandatory, with vehicle models either being independently chosen by Euro NCAP or sponsored by the manufacturers. In Europe, new cars are certified as legal for sale under the Whole Vehicle Type Approval regimen that differs from Euro NCAP. According to Euro NCAP, "The frontal and side impact crash tests used by Euro NCAP are based on those used in European legislation. However, much higher performance requirements are used by Euro NCAP. Euro NCAP also states that "Legislation sets a minimum compulsory standard whilst Euro NCAP is concerned with best possible current practice. Progress with vehicle safety legislation can be slow, particularly as all EU Member States’ views have to be taken into account. Also, once in place, legislation provides no further incentive to improve, whereas Euro NCAP provides a continuing incentive by regularly enhancing its assessment procedures to stimulate further improvements in vehicle safety."