This research adressed some road safety problems related to the motion of heavy vehicles in some places of the San José county, focusing the analisys on some locations of the No.1 and No.39 highways. This was made by relating a qualitative and quantitative analisys of the heavy vehicles' maneuverability with the geometric and topographic characteristics of some selected places, with the traffic accidents, and with the mechanical characteristics of some heavy vehicles. Hence, the posibility of implementing some road safety improvements was identified, improvements that are related to the modification of the design of some roundabouts and access ramp. Besides, it was proved that the heavy vehicle drivers do not have stopping sight distance conflicts on some road segments chosen. Finally a quantitative analisys of the stability of some heavy vehicles pointed out that, under normal driving conditions, those vehicles should not have stability problems on the horizontal curves were some rollovers occured.