The passenger compartment of the Z4 remained stable in the frontal offset test. Dummy readings indicated good protection of the knees and femurs of the driver and passenger. BMW demonstrated that a similar level of protection would be provided to occupants of different sizes and to those sitting in different positions. In the full-width rigid barrier test, protection of the driver was good or adequate for all critical body areas. In the side barrier test, all critical parts of the body were well protected and the car scored maximum points. Likewise, full points were scored in the more severe side pole test, with good protection all-round. Tests on the seats and head restraints demonstrated good protection against whiplash injuries in the event of a rear-end collision. The Z4 has a standard-fit autonomous emergency braking (AEB) system which operates at the low speeds, typical of city driving, at which many whiplash injuries occur. In tests of this functionality, the system scored maximum points, with collisions against another vehicle avoided in all test scenarios.

Good protection was provided to the six-year dummy, sat in the front passenger seat, in both the frontal offset and side barrier tests. Protection of the ten-year child was not assessed. The passenger airbag can be disabled to allow a rearward-facing child restraint to be used in that seating position. Clear information is provided to the driver regarding the status of the airbag and the system was rewarded. The passenger seat is not approved to for the installation of one type of ISOFIX restraint.  Otherwise, all of the restraints for which the Z4 is designed could be properly installed and accommodated in the car.

The Z4 has an 'active' bonnet, or hood. Sensors detect when a pedestrian has been struck and actuators raise the bonnet to increase the distance to hard structures in the engine compartment. BMW showed that the system worked robustly for a variety of pedestrian statures and across a range of speeds. Accordingly, the bonnet was tested in the deployed, raised position. Test results were almost exclusively good or adequate. The bumper provided good protection to pedestrians' legs, and protection of the pelvis was also rated as good. The AEB system can detect vulnerable road users like pedestrians and cyclists, as well as other vehicles. In tests, the system performed adequately in its response to pedestrians and, for cyclists, its performance was rated as good.

The AEB system performed well in tests of its response to other vehicles at highway speeds, with collisions avoided in the great majority of test scenarios. There is a seatbelt reminder system as standard. A lane support system helps to prevent inadvertent drifting out of lane. The speed assistance system uses a camera to detect the local speed limit. This information is presented to the driver, allowing the limiter to be set appropriately.