The Peugeot 408 is very closely related to the 308 tested earlier in 2022.  Some additional tests have been performed on the 408 but the rating is largely based on the results of the 308.

The passenger compartment remained stable in the frontal offset test. Dummy numbers showed good protection of the knees and femurs of both the driver and passenger. Peugeot showed that a similar level of protection would be provided to occupants of different sizes and to those sitting in different positions. For the driver, dummy readings of chest compression indicated a weak level of protection for that part of the body, and protection of the lower leg was marginal. Analysis of the deceleration of the impact trolley during the test, and analysis of the deformable barrier after the test, revealed that the car would be a moderately benign impact partner in a frontal collision. In the full-width rigid barrier test, protection of the driver’s chest was rated as marginal, based on dummy readings of chest compression, with that of all other critical body areas rated as good or adequate.  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. Even in the more severe side pole impact, protection of the chest was adequate and that of other body areas good.  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 marginal. There is no counter-measure, such as a centre airbag, to mitigate against occupant to occupant injuries in such impacts. 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 408 lacks an advanced eCall system which alerts the emergency services in the event of a crash.   The car also has a system which applies the brakes after an impact, to avoid secondary collisions.

In the frontal offset test, protection of the neck of the 10-year dummy was rated as marginal, based on dummy readings of tensile forces.  Otherwise, for this test, protection of critical body areas was good or adequate.  In the side barrier test, protection of all critical body areas was good.  The front 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.  With the exception of the large universal CRS, which was unstable in the rear centre seat, all of the child restraint types for which the car is designed could be properly installed and accommodated.

The 408 has an 'active' bonnet.  Sensors in the bumper detect when a pedestrian has been struck and actuators lift the bonnet to increase clearance to hard structures in the engine compartment.  Peugeot showed that the system worked robustly for different pedestrian statures and over a range of speeds.  Accordingly, the car was tested with the bonnet in the raised, 'deployed' position.  The protection offered to the head of a struck pedestrian was mostly good over the bonnet surface, with some poor results recorded elsewhere.  The bumper provided good protection to pedestrians’ legs at all test points and the protection provided to the pelvis by the front edge of the bonnet was also good across the width of the car.  The autonomous emergency braking (AEB) system can respond to vulnerable road users as well as to other vehicles.  The system performed adequately in tests of its response to pedestrians.  The system’s response to cyclists was good, with collisions avoided in many test scenarios.

A seatbelt reminder system is standard on the front and rear seating positions.  The AEB system performed only marginally in tests of its response to other vehicles.  A camera-based speed assistance system identifies the local speed limit and provides the information to the driver, allowing the limiter to be set appropriately.  A lane support system gently corrects the vehicle’s path if it is drifting out of lane and intervenes more aggressively in some more critical situations.