The Phantom has standard whiplash protection, which use a specially designed headrest to protect the driver and front passenger from whiplash. During a rear-end collision, the whiplash protection system moves the headrests forward to prevent neck and spine injuries. The S8 doesn’t offer a whiplash protection system.
The Phantom 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 S8’s blind spot costs extra.
To help make backing out of a parking space safer, the Phantom 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 S8.
The Phantom’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 S8 doesn’t offer a driver alert monitor.
Both the Phantom and the S8 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, post-collision automatic braking systems, daytime running lights, lane departure warning systems and around view monitors.
The Rolls-Royce Phantom weighs 452 to 562 pounds more than the Audi S8. The NHTSA advises that heavier cars are much safer in collisions than their significantly lighter counterparts.