For enhanced safety, the front and rear seat shoulder belts of the BMW 4 Series Convertible have pretensioners to tighten the seatbelts and eliminate dangerous slack in the event of a collision. The MINI Cooper Convertible doesn’t offer pretensioners for its rear seat belts.
The 4 Series Convertible’s pre-crash front seatbelts will tighten automatically in the event the vehicle detects an impending crash, improving protection against injury significantly. The Cooper Convertible doesn’t offer pre-crash pretensioners.
The 4 Series Convertible has standard front and rear seat tall, head-protecting side-impact airbags, which act as a forgiving barrier between the passengers and the door. Combined with high-strength steel door beams this system increases protection from broadside collisions. The Cooper Convertible doesn't offer rear-seat side-impact airbags, only ones for front seat occupants.
The 4 Series Convertible’s standard pretensioning seatbelts also sense rear collisions and remove slack from the seatbelts to help protect the occupants from whiplash and other injuries. The Cooper Convertible doesn’t offer a whiplash protection system.
Over 200 people are killed each year when backed over by motor vehicles. The 4 Series Convertible M440i offers an optional Active Park Distance Control that uses rear sensors to monitor for objects to the rear and automatically applies the brakes to prevent a collision. The Cooper Convertible doesn’t offer backup collision prevention brakes.
The 4 Series Convertible offers all-wheel drive to maximize traction under poor conditions, especially in ice and snow. The Cooper Convertible doesn’t offer all-wheel drive.
The 4 Series Convertible M440i offers an optional Surround View to allow the driver to see objects all around the vehicle on a screen. The Cooper Convertible only offers a rear monitor and front and rear parking sensors that beep or flash a light. That doesn’t help with obstacles to the sides.
The 4 Series Convertible’s blind spot warning system uses sensors to alert the driver to objects in the vehicle’s blind spots where the side view mirrors don’t reveal them and moves the vehicle back into its lane. The Cooper Convertible doesn’t offer a system to reveal objects in the driver’s blind spots.
To help make backing out of a parking space safer, the 4 Series Convertible’s standard Cross Traffic Warning uses sensors in the rear to alert the driver to vehicles approaching from the side, helping the driver avoid collisions. The Cooper Convertible doesn’t offer a rear cross-path warning system.
Both the 4 Series Convertible and the Cooper Convertible 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 and driver alert monitors.
The BMW 4 Series Convertible weighs 739 to 1300 pounds more than the MINI Cooper Convertible. The NHTSA advises that heavier cars are much safer in collisions than their significantly lighter counterparts. Crosswinds also affect lighter cars more.