The S5’s pre-crash front seatbelts will tighten automatically in the event the vehicle detects an impending crash, improving protection against injury significantly. The 718 Boxster doesn’t offer pre-crash pretensioners.
The S5’s standard pretensioning seatbelts also sense rear collisions and remove slack from the seatbelts to help protect the occupants from whiplash and other injuries. The 718 Boxster doesn’t offer a whiplash protection system.
The S5 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 718 Boxster 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 S5 has all-wheel drive to maximize traction under poor conditions, especially in ice and snow. The 718 Boxster doesn’t offer all-wheel drive.
The S5’s 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. The 718 Boxster doesn’t offer a lane departure warning system.
The S5 Premium Plus/Prestige has a standard Top View Cameras to allow the driver to see objects all around the vehicle on a screen. The 718 Boxster only offers a rear monitor and front and rear parking sensors that beep. That doesn’t help with obstacles to the sides.
To help make backing out of a parking space safer, the S5 Premium Plus/Prestige’s standard Rear Cross-Traffic Assist uses sensors in the rear to alert the driver to vehicles approaching from the side and Automatic Brake Activation automatically engages the brakes to help avoid a collision. The 718 Boxster doesn’t offer a rear cross-path warning system.
Both the S5 and the 718 Boxster have standard driver and passenger frontal airbags, front side-impact airbags, driver and front passenger knee airbags, side-impact head airbags, front seatbelt pretensioners, four-wheel antilock brakes, traction control, electronic stability systems to prevent skidding, daytime running lights, rearview cameras and available blind spot warning systems.
The Audi S5 weighs 623 to 1147 pounds more than the Porsche 718 Boxster. The NHTSA advises that heavier cars are much safer in collisions than their significantly lighter counterparts.