Research on Setting of Freeway Lower Velocity Limit for Trucks

The influence of trucks' velocity on the Level of Service is studied on the basis of VISSIM with the criterion of the boundary influence of trucks' velocity on cars' equaling to one.Key velocity of trucks is obtained to ensure freeway in a better operation.The velocity of 60 km·h-1 is proposed to be the lowest limit for freeway with at least two lanes in one direction.Results show that the car speed will be increased by 10 km·h-1 or so when the 60 km·h-1 speed limit for trucks is put into effect.The level of service is no less than two at present and will be no less than three in future even if the traffic flow increases to 3 000 veh·h-1.