The A4’s pre-crash front seatbelts will tighten automatically in the event the vehicle detects an impending crash, improving protection against injury significantly. The WRX doesn’t offer pre-crash pretensioners.
Both the A4 and WRX have child safety locks to prevent children from opening the rear doors. The A4 has power child safety locks, allowing the driver to activate and deactivate them from the driver's seat and to know when they're engaged. The WRX’s child locks have to be individually engaged at each rear door with a manual switch. The driver can’t know the status of the locks without opening the doors and checking them.
The Audi A4 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 WRX doesn’t offer a front passenger side knee airbag.
The A4 has a standard Secondary Collision Brake Assist, which automatically applies the brakes in the event of a crash to help prevent secondary collisions and prevent further injuries. The WRX 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 A4’s standard lane departure warning system alerts a temporarily inattentive driver when the vehicle begins to leave its lane. A lane departure warning system costs extra on the WRX.
The A4 Premium Plus/Prestige has a standard Top and Corner View Cameras to allow the driver to see objects all around the vehicle on a screen. The WRX only offers a rear monitor.
The A4 has a standard Audi Connect CARE, which uses a global positioning satellite (GPS) receiver and a cellular system to help track down your vehicle if it’s stolen or send emergency personnel to the scene if any airbags deploy. The WRX doesn’t offer a GPS response system, only a navigation computer with no live response for emergencies, so if you’re involved in an accident and you’re incapacitated help may not come as quickly.
Both the A4 and the WRX have standard driver and passenger frontal airbags, front side-impact airbags, driver knee airbags, side-impact head airbags, four-wheel antilock brakes, all wheel drive, traction control, electronic stability systems to prevent skidding, rearview cameras, available blind spot warning systems and rear cross-path warning.
For its top level performance in IIHS driver and passenger-side small overlap frontal, moderate overlap frontal, side impact, roof strength and head restraint tests, its standard vehicle-to-vehicle front crash prevention system, its standard vehicle-to-pedestrian front crash prevention system, and its available headlight’s “Good” rating, the Insurance Institute for Highway Safety grants the A4 the rating of “Top Safety Pick” for 2021, a rating granted to only 145 vehicles tested by the IIHS. The WRX has not been tested, yet.