Aerodynamic Hoods, Fenders & Headlamps
The characteristic shapes of aerodynamic sleeper models generally have rounded leading edges, especially at the crown and grille edges, cab A-pillars, and sleeper roof edges. They also generally have conformal headlamps integrated into fenders, curved outer ends to bumpers, bumper air dams, hoods that slope downward at the front, aerodynamic cab access steps, chassis fairings with ground effects skirting, and sleeper extenders. These features are mandatory for vehicles to be classified by the EPA as SmartWay tractors.
Since the early 2000s, aerodynamic sleepers have become the predominant type of tractors in production. Classic sleepers still exist with long and tall hoods, but sacrifice as much as 30% in fuel savings.
Headlamps on aerodynamic tractors are designed as integral parts of the hood shape. Some the OEMs have contoured the headlamps to conform to the body shape. Other OEM models may offer headlamp alternatives, but the aerodynamic flagship models have been aerodynamically optimized around single shapes.
Due to lower drag.
Drivers can see objects directly in front of the vehicle and to the forward right and left sides of the tractor.
Vehicle cooling systems require air flow over a given amount of radiator surface, so there is always a required amount of the hood that is open for air flow.