I should also add that the effect of drag increases as a square of speed, specifically the formula is: Force due to Drag = Cd x Frontal Area x Air Density x Speed^2
So the drag force at 70 mph is over twice that while traveling 48 mph. --> (70*70)/(48*48) = 2.1
So the drag force at 70 mph is over twice that while traveling 48 mph. --> (70*70)/(48*48) = 2.1