In the frontal offset test, the passenger compartment of the B-Class remained stable. Dummy readings indicated good protection of the knees and femurs of both the driver and passenger. Mercedes-Benz showed that a similar level of protection would be provided to occupants of different sizes and to those sitting in different positions. Protection of the front passenger was good for all critical body areas. In the full-width rigid barrier test, protection of the driver was good or adequate for all critical body areas. For the rear passenger, dummy readings of chest compression indicated marginal protection for that body area but protection was otherwise good or adequate. In the side barrier impact, protection was good for all body areas and the car scored maximum points. In the more severe side pole test, protection of the chest was adequate and that of other critical body areas was good. Tests on the front seats and head restraints demonstrated good protection against whiplash injuries in the event of a rear-end collision. A geometric assessment of the rear seats also indicated good whiplash protection. The standard-fit autonomous emergency braking (AEB) system performed well in tests of its functionality at the low speeds at which many whiplash injuries occur.

In the frontal offset test, protection of both the 6 and 10 year dummies was good or adequate for all critical body areas. In the side barrier test, protection was good for both dummies and the car scored maximum points for this part of the assessment. The front passenger airbag is automatically disabled when a rearward-facing child restraint is put in that seating position. Tests showed that the system worked robustly and the system was rewarded. All of the child restraint types for which the B-Class is designed could be properly installed and accommodated.

The protection provided by the bonnet to the head of a struck pedestrian was predominantly good or adequate, with some areas of poor protection only on the stiff windscreen pillars. The bumper provided good protection to pedestrians' legs and protection of the pelvis was also predominantly good. The AEB system can detect vulnerable road users like pedestrians and cyclists, as well other cars. Tests of the system's response to pedestrian demonstrated good performance. The B-Class scored maximum points in tests of its detection of cyclists.

The B-Class has a seatbelt reminder for the front and rear seats. The standard-fit AEB system performed well in tests of its response to other vehicles at highway speeds. A camera-based speed limit recognition system advises the driver of the local limit, and allows easy activation of the speed limiter. A lane support system helps the driver to avoid inadvertent drifting out of lane and also intervenes in some more critical situations.