For enhanced safety, the front and rear seat shoulder belts of the Mercedes C-Class Sedan 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 3 Series Sedan doesn’t offer pretensioners for its rear seat belts.
For enhanced safety, the front seat shoulder belts of the Mercedes C-Class Sedan 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 3 Series Sedan doesn’t offer height-adjustable seat belts.
Earlier warning of stopped traffic, traffic signals, dangerous road conditions, weather, or accidents, can keep driver's safer and prevent crashes. The C-Class Sedan offers optional Car-to-X Communication, a system that seemlesly communicates important warnings to the driver about impending danger, if they're available. The 3 Series Sedan doesn’t offer a system that can receive automated systems from infrastructure or other vehicles.
The C-Class Sedan has a standard blind spot warning system that uses sensors to alert the driver to objects in the vehicle’s blind spots where the side view mirrors don’t reveal them. A system to reveal vehicles in the 3 Series Sedan’s blind spot costs extra.
Both the C-Class Sedan and 3 Series Sedan offer rear cross-traffic warning, but the C-Class Sedan with Rear Cross-Traffic Alert also has Active Brake Assist (automatically applies the brakes) to better prevent a collision when backing near traffic. The 3 Series Sedan’s Cross Traffic Warning doesn’t automatically brake.
Both the C-Class Sedan and the 3 Series Sedan have standard driver and passenger frontal airbags, front side-impact airbags, driver knee airbags, side-impact head airbags, four-wheel antilock brakes, traction control, electronic stability systems to prevent skidding, crash mitigating brakes, post-collision automatic braking systems, daytime running lights, rearview cameras, driver alert monitors, available all wheel drive and around view monitors.
For its top level performance in IIHS driver and passenger-side small overlap frontal, moderate overlap frontal, side impact, roof strength and head restraint tests, with its optional vehicle-to-vehicle front crash prevention system, with its optional vehicle-to-pedestrian front crash prevention system, and its standard headlight’s “Good” rating, the Insurance Institute for Highway Safety grants the C-Class Sedan its highest rating: “Top Safety Pick Plus” for 2022, a rating granted to only 131 vehicles tested by the IIHS. The 3 Series Sedan has not been fully tested, yet.