6.6 A freeway is being designed for a location in mountainous terrain. The expected free-flow speed is 55 mi/h. Lane widths will be 12 ft and shoulder widths will be 6 ft. During the peak hour, it is expected there will be a directional peak-hour volume of 2700 vehicles, 12% large trucks and buses and 6% recreational vehicles. The PHF and driver population adjustment are expected to be 0.88 and 0.90, respectively. If a level of service no worse than D is desired, determine the necessary number of lanes.