The 4 Series Gran Coupe’s pre-crash front seatbelts will tighten automatically in the event the vehicle detects an impending crash, improving protection against injury significantly. The Legacy doesn’t offer pre-crash pretensioners.
The BMW 4 Series Gran Coupe has standard driver and front passenger side knee airbags mounted low on the dashboard. These airbags helps prevent the driver and front passenger from sliding under their seatbelts or the main frontal airbags; this keeps them better positioned during a collision for maximum protection. Knee airbags also help keep the legs from striking the dashboard, preventing knee and leg injuries in the case of a serious frontal collision. The Legacy doesn’t offer a front passenger side knee airbag.
The 4 Series Gran Coupe has a standard PostCrash iBrake, which automatically applies the brakes in the event of a crash to help prevent secondary collisions and prevent further injuries. The Legacy doesn’t offer a post collision braking system: in the event of a collision that triggers the airbags, more collisions are possible without the protection of airbags that may have already deployed.
The 4 Series Gran Coupe has standard Park Distance Control to help warn the driver about vehicles, pedestrians or other obstacles behind or in front of their vehicle. The Legacy doesn’t offer a front parking aid.
The 4 Series Gran Coupe has a standard blind spot warning system which uses sensors to alert the driver to objects in the vehicle’s blind spots where the side view mirrors don’t reveal them and moves the vehicle back into its lane. A system to reveal vehicles in the Legacy’s blind spot costs extra.
To help make backing out of a parking space safer, the 4 Series Gran Coupe has a standard rear cross-path warning system, which uses sensors in the rear bumper to alert the driver to vehicles approaching from the side, helping the driver avoid collisions. Rear cross-path warning costs extra on the Legacy and isn't available on the not available.
Compared to metal, the 4 Series Gran Coupe’s plastic fuel tank can withstand harder, more intrusive impacts without leaking; this decreases the possibility of fire. The Subaru Legacy has a metal gas tank.
Both the 4 Series Gran Coupe and the Legacy have standard driver and passenger frontal airbags, front side-impact airbags, driver knee airbags, side-impact head airbags, front seatbelt pretensioners, four-wheel antilock brakes, traction control, electronic stability systems to prevent skidding, crash mitigating brakes, daytime running lights, lane departure warning systems, rearview cameras and available all wheel drive.