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.
When descending a steep, off-road slope, the A4’s standard Hill Descent Control allows you to creep down safely. The WRX doesn’t offer Hill Descent Control.
The A4’s standard lane departure warning system alerts a temporarily inattentive driver when the vehicle begins to leave its lane and gently nudges the vehicle back towards 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 and rear parking sensors that beep or flash a light. That doesn’t help with obstacles to the front or sides.
Both the A4 and WRX offer rear cross-traffic warning, but the A4 with Rear Cross-Traffic Assist also has Automatic Brake Activation (automatically applies the brakes) to better prevent a collision when backing near traffic. The WRX’s Rear Cross Traffic Alert doesn’t automatically brake.
Both the A4 and the WRX have standard driver and passenger frontal airbags, front side-impact airbags, driver knee airbags, side-impact head airbags, front and rear seatbelt pretensioners, height adjustable front shoulder belts, four-wheel antilock brakes, all wheel drive, traction control, electronic stability systems to prevent skidding, daytime running lights, rearview cameras and available blind spot warning systems.

