The crash parameters of horizontal curves and geometric design roads, effective in the crash and as dependent variables have been described here for some countries in the world. The major issues pertaining to transportation safety and factors that affect crashes with emphasis on horizontal curves in two lane rural roads are also explained. The reviews on the crashes on two lane rural roads indicated that horizontal curves and geometric design variables such as: radius curve, degree curve, deflection angle super-elevation in curve, width in curve, width shoulder, speed, length curve, grade of...