For enhanced safety, the front and rear seat shoulder belts of the Audi S4 have pretensioners to tighten the seatbelts and eliminate dangerous slack in the event of a collision and force limiters to limit the pressure the belts will exert on the passengers. The BMW 4 Series Gran Coupe doesn’t offer pretensioners for its rear seat belts.
For enhanced safety, the front seat shoulder belts of the Audi S4 are height-adjustable to accommodate a wide variety of driver and passenger heights. A better fit can prevent injuries and the increased comfort also encourages passengers to buckle up. The BMW 4 Series Gran Coupe doesn’t offer height-adjustable seat belts.
Both the S4 and 4 Series Gran Coupe 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 4 Series Gran Coupe’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.
To provide maximum traction and stability on all roads, All-Wheel Drive is standard on the S4. But it costs extra on the 4 Series Gran Coupe.
Both the S4 and 4 Series Gran Coupe offer rear cross-traffic warning, but the S4 with Rear Cross-Traffic Assist also has Automatic Brake Activation (automatically applies the brakes) to better prevent a collision when backing near traffic. The 4 Series Gran Coupe’s Cross Traffic Warning doesn’t automatically brake.
Both the S4 and the 4 Series Gran Coupe have standard driver and passenger frontal airbags, front side-impact airbags, driver and front passenger knee airbags, side-impact head airbags, plastic fuel tanks, four-wheel antilock brakes, traction control, electronic stability systems to prevent skidding, crash mitigating brakes, post-collision automatic braking systems, daytime running lights, lane departure warning systems, rearview cameras, available blind spot warning systems and around view monitors.