Why must a bus driver brake smoothly and slow gradually for curves with passengers aboard?

Many bus passengers are not belted, and some may be standing, so the driver's braking and cornering directly affect their safety. Hard braking can pitch riders forward, and entering a curve too fast can throw them sideways or cause the bus to lose stability. The driver should slow to a safe speed before the curve, then hold a steady speed through it, and brake early and gently for stops. Smooth operation keeps passengers secure in their seats and the heavy vehicle under control, which is why the manual emphasizes anticipating stops and curves well in advance.