The passenger compartment of the Polestar 4 remained stable in the frontal offset test.  Dummy readings indicated good protection of the knees and femurs of both the driver and the front seat passenger. Polestar showed that a similar level of protection would be provided to occupants of different sizes and to those sitting in different positions.  Analysis of the deceleration of the impact trolley during the test, and analysis of the deformable barrier after the test, revealed that the Polestar 4 would be a moderately benign impact partner in a frontal collision.  In the full-width rigid barrier test, protection was good for all critical body regions of the rear seat passenger and at least adequate for the driver.    In both the side barrier test and the more severe side pole impact, good protection was provided to all critical body areas and the Polestar 4 scored maximum points in this part of the assessment.  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 adequate  The Polestar 4 has a countermeasure to mitigate against occupant-to-occupant injuries in such impacts.  The airbag performed well in Euro NCAP’s tests with dummy readings indicating good protection for both the driver and passenger.  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 car has an advanced eCall system which alerts the emergency services in the event of a crash, and a  system to prevent secondary impacts after the car has been in a collision.  Polestar demonstrated that the doors and windows would be openable to allow occupants to escape in the event of vehicle submergence.

In both the frontal offset and the side barrier tests, protection was good for all critical body areas for the 6 and 10 year dummies, and the Polestar 4 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 is provided to the driver regarding the status of the airbag and the system was rewarded.  The Polestar 4 is equipped with a direct 'child presence detection' system, which issues a warning when it detects that a child or infant has been left in the car. All of the child restraint types for which the Polestar 4 is designed could be properly installed and accommodated in the car.

Protection of the head of a struck pedestrian or cyclist was largely good or adequate, with poor results recorded only on the stiff windscreen pillars and at the base and top of the screen.   Protection of the pelvis was mostly good. Protection of the femur was good at all test locations, while that of the knee and tibia was good at all test locations  The autonomous emergency braking system of the Polestar 4 responds to vulnerable road users such as pedestrians and cyclists, as well as to other vehicles.  In tests of its response to pedestrians and cyclists, the system performed well andits response to motorcyclists was also good.

Overall, the performance of the autonomous emergency braking (AEB) system was good in tests of its reaction to other vehicles.  A seatbelt reminder system is fitted as standard to the front and rear seats.  The car has a direct driver status monitoring system as standard, detecting driver fatigue and some types of distraction.  However, the system does not immediately operate from Euro NCAP’s required minimum speed and was not rewarded.  The lane support system gently corrects the vehicle’s path if it is drifting out of lane and also intervenes in some more critical situations.  The speed assistance system identifies the local speed limit.  The driver can use the adaptive cruise control to control the speed of the car.