The Mercedes-Benz GLA shares much of its structure with the B-Class tested in 2019. Additional tests have been performed where necessary but some tests have been carried over, so the GLA carries a 2019 rating, as does the B-Class.

In the frontal offset test, the passenger compartment of the GLA 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 GLA is designed could be properly installed and accommodated.

Unlike the B-Class, the GLA has an 'active' bonnet.  Sensors in the bumper detect when a pedestrian has been struck and actuators lift the bonnet to create more space to the stiff structures in the engine compartment.  Mercedes-Benz demonstrated that the system worked robustly for different pedestrian statures and over a range of speeds.  Accordingly, tests were performed with the bonnet in the raised 'deployed' position.  Test results demonstrate good or adequate protection to the head of a struck pedestrian over almost all of the bonnet surface.  Protection of pedestrians' legs was good aty all test locations but protection of the pelvis was poor.  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 GLA scored maximum points in tests of its detection of cyclists.

The GLA 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.