The Volvo S90 offers optional built in child booster seats. They’re more crash worthy than an added child seat because of their direct attachment to the seat. Audi doesn’t offer the convenience and security of a built-in child booster seat in the A6. Their owners must carry a heavy booster seat in and out of the vehicle; S90 owners can just fold their built-in child seat up or down.
The S90 has a standard Whiplash Protection System (WHIPS), which use a specially designed headrest to protect the driver and front passenger from whiplash. During a rear-end collision, the WHIPS moves the headrests forward to prevent neck and spine injuries. At the same time the pretensioning seatbelts fire, removing slack from the belts. The A6 doesn’t offer a whiplash protection system.
The S90 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. A system to reveal vehicles in the A6’s blind spot costs extra.
To help make backing out of a parking space safer, the S90 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 A6.
The S90’s driver alert monitor detects an inattentive driver then sounds a warning and suggests a break. According to the NHTSA, drivers who fall asleep cause about 100,000 crashes and 1500 deaths a year. The A6 doesn’t offer a driver alert monitor.
Both the S90 and the A6 have standard driver and passenger frontal airbags, front and rear 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, crash mitigating brakes, post-collision automatic braking systems, daytime running lights, lane departure warning systems and rearview cameras.