Local Road Management Manual 90 at will on the pavement. Gradients would have a lowering impact on bus speeds. Carriageway and shoulder widths impact on road capacity for buses and trucks, especially for pavement widths of less than 6 meters. Lack of or limited shoulder and its condition also limit road capacity because it would imply the similarity of lateral obstructions; and e. Trucks. PCEF = 2.0 for a rigid truck and 2.5 for a semi- or trailer-truck combination. As trucks do not stop regularly roadside friction is not a restraining factor but gradients and their lengths have a substantial effect on heavily loaded (or overloaded) trucks. Table 3.9 Typical Passenger Car Equivalent Factors (PCEF) to Convert Traffic Volume into Passenger Car Units (PCU) Vehicle Type Passenger Car Equvalence Factor (PCEF) No. Description Flat Rolling Mountainous 1 Motor-tricycle/Motorcycle 0.5 0.5 0.5 2 Passenger Car 1 1 1 3—5 Passenger and good utili- 1.5 1.73 1.95 ty and small bus 6 Large bus 2 2.3 2.6 7 Rigid truck, 2 axles 2 2.3 2.6 8 Rigid truck, 3+ axles 2.5 2.88 3.25 9 Truck semi—trailer, 3 and 2.5 2.88 3.25 4 axles 10 Truck semi—trailer, 5+ 2.5 2.88 3.25 axles 11 Trailer trucks, 4 axles 2.5 2.88 3.25 12 Trailer trucks, 5 axles 2.5 2.88 3.25