The Z4’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 Z4’s optional 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 Z4’s optional cross-path warning system uses sensors in the rear bumper to alert the driver to vehicles approaching from the side, helping the driver avoid collisions. The Cooper Convertible doesn’t offer a cross-path warning system.
Both the Z4 and the Cooper Convertible have standard driver and passenger frontal airbags, front side-impact airbags, driver and front passenger knee airbags, front seatbelt pretensioners, 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 lane departure warning systems and rear parking sensors.

