A number of studies show that drivers of vehicles with ABS tend to drive faster, follow closer and brake later, accounting for the failure of ABS to result in any measurable improvement in road safety. The studies were performed in Canada, Denmark, and Germany.[13][14][15] A study led by Fred Mannering, a professor of civil engineering at the University of South Florida supports risk compensation, terming it the "offset hypothesis".[16] A study of crashes involving taxicabs in Munich of which half had been equipped with anti-lock brakes noted that crash rate was substantially the same for both types of cab, and concluded this was due to drivers of ABS-equipped cabs taking more risks.[17]