The mechanical condition of vehicles and their characteristics for accelerating, decelerating, stopping, and turning definitely affect safe speeds.

The body roll angle of different makes of cars and year models of the same make also affects the safe operating speed on curves.

Braking capabilities of different vehicles, such as passenger cars, buses, and various truck-trailer combinations, are obviously different, and it would generally not be practical to post safe speeds for each group.

Normally, the posted speed will be that for the passenger car.