Both the S4 and AMG C-Class Sedan have child safety locks to prevent children from opening the rear doors. The S4 has power child safety locks, allowing the driver to activate and deactivate them from the driver's seat and to know when they're engaged. The AMG C-Class Sedan’s child locks have to be individually engaged at each rear door with a manual switch. The driver can’t know the status of the locks without opening the doors and checking them.
The S4 has a standard Secondary Collision Brake Assist, which automatically applies the brakes in the event of a crash to help prevent secondary collisions and prevent further injuries. The AMG C-Class Sedan doesn’t offer a post collision braking system: in the event of a collision that triggers the airbags, more collisions are possible without the protection of airbags that may have already deployed.
To provide maximum traction and stability on all roads, All-Wheel Drive is standard on the S4. But it costs extra on the AMG C-Class Sedan.
The S4’s standard lane departure warning system alerts a temporarily inattentive driver when the vehicle begins to leave its lane. A lane departure warning system costs extra on the AMG C-Class Sedan.
Both the S4 and the AMG C-Class Sedan have standard driver and passenger frontal airbags, front side-impact airbags, driver and front passenger knee airbags, side-impact head airbags, front and rear seatbelt pretensioners, height adjustable front shoulder belts, plastic fuel tanks, four-wheel antilock brakes, traction control, electronic stability systems to prevent skidding, crash mitigating brakes, daytime running lights, rearview cameras, available blind spot warning systems, around view monitors and rear cross-path warning.
Instrumented handling tests conducted by the National Highway Traffic Safety Administration and analysis of its dimensions indicate that the S4, with its five-star roll-over rating, is 1.1% less likely to roll over than the AMG C-Class Sedan, which received a four-star rating.