The MX-5 Miata has standard tall side airbags which act as a forgiving barrier between the driver and outboard passenger's upper bodies and the window and pillars. Combined with high-strength steel door beams and lower side airbags this system increases head protection in broadside collisions. The Z4 doesn't offer side airbag protection for the head.
The MX-5 Miata’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 Z4.
The MX-5 Miata has a standard blind spot warning system which 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 Z4’s blind spot costs extra.
To help make backing out of a parking space safer, the MX-5 Miata has a standard rear cross-path warning system, which uses sensors in the rear bumper to alert the driver to vehicles approaching from the side, helping the driver avoid collisions. Rear cross-path warning costs extra on the Z4.
Both the MX-5 Miata and the Z4 have standard driver and passenger frontal airbags, front side-impact airbags, front seatbelt pretensioners, four-wheel antilock brakes, traction control, electronic stability systems to prevent skidding, crash mitigating brakes, daytime running lights and rearview cameras.

