The passenger compartment of the DS 4 remained stable in the frontal offset test. Dummy numbers showed good protection of the knees and femurs of both the driver and passenger. DS showed that a similar level of protection would be provided to occupants of different sizes and to those sitting in different positions.  Dummy readings of compression indicated marginal protection of the driver’s chest.  Analysis of the deceleration of the impact trolley during the test, and analysis of the deformable barrier after the test, revealed that the DS 4 would be a moderately aggressive impact partner in a frontal collision. In the full width rigid barrier test, readings of chest compression in the front seat dummy indicated a marginal level of protection for this body area, but that of all others was good or adequate for both the driver and rear seat passenger. In the side barrier test, protection of all critical body areas was good and the car scored maximum points in this part of the assessment. In the more severe side pole impact, protection of the chest was rated as marginal. Control of excursion (the extent to which a body is thrown to the other side of the vehicle when it is hit from the far side) was found to be good.  The DS 4 has a counter-measure to mitigate against occupant to occupant injuries in such impacts and this performed well in Euro NCAP's test. Tests on the front seats and head restraints demonstrated good protection against whiplash injuries in the event of a rear-end collision.  A geometric analysis of the rear seats also indicated good whiplash protection.   The DS 4 has an advanced eCall system which alerts the emergency services in the event of a crash but this is part of the optional 'Safety Pack Plus' and was not included in the assessment.   The car also has a system which applies the brakes after an impact to avoid secondary collisions.

In the frontal offset test, the protection of all critical body areas was good or adequate.  In the side barrier test, protection of all body areas was good for both dummies and the car scored maximum points in this part of the assessment.  The front passenger airbag can be disabled to allow a rearward-facing child restraint to be used in that seating position.  Clear information regarding the status of the airbag is provided to the driver and the system was rewarded.  The user manual does not identify the rear centre seat as suitable for the Group II/III universal restraint but, otherwise, maximum points were scored for the installation of restraints.

The DS4 has an ‘active bonnet’. Sensors in the bumper recognise when a pedestrian has been hit and actuators lift the bonnet surface to provide greater clearance to stiff structure in the engine compartment.  DS showed that the system worked robustly for different pedestrian statures and across a range of speeds and, accordingly, the car was tested with the bonnet in the raised, deployed position.  The bonnet surface provided good or adequate protection over almost all of its surface, with poor results recorded at the base of the windscreen and on the stiff windscreen pillars.  The bumper provided good protection to pedestrians’ legs at all test locations.  However, the protection provided to the pelvis was more mixed.  The autonomous emergency braking system of the DS4 can recognise vulnerable road users, as well as other vehicles.  The system reacted adequately to pedestrians and performed well in tests of its response to cyclists.

The DS4 has a seatbelt reminder system for the front and rear seats.  The AEB system performed only marginally well in tests of its reaction to other cars.  A lane support system gently corrects the vehicle’s path if it is drifting out of lane and also intervenes in some more critical situations.  Speed assistance is provided by a system which recognises the local limit, allowing the speed limiter to be set as appropriate.