For enhanced safety, the front and rear seat shoulder belts of the Mercedes AMG SL have pretensioners to tighten the seatbelts and eliminate dangerous slack in the event of a collision and force limiters to limit the pressure the belts will exert on the passengers. The Porsche 911 doesn’t offer pretensioners for its rear seat belts.
The AMG SL’s pre-crash front seatbelts will tighten automatically in the event the vehicle detects an impending crash, improving protection against injury significantly. The 911 doesn’t offer pre-crash pretensioners.
The Mercedes AMG SL 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 911 doesn’t offer knee airbags.
The AMG SL offers an optional Post Collision Brake, which automatically applies the brakes in the event of a crash to help prevent secondary collisions and prevent further injuries. The 911 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.
Over 200 people are killed each year when backed over by motor vehicles. The AMG SL has a standard Maneuvering Brake that uses rear sensors to monitor for objects to the rear and automatically applies the brakes to prevent a collision. The 911 doesn’t offer automatic braking for stationary objects directly to the rear.
The AMG SL has a standard blind spot warning system that 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 911’s blind spot costs extra.
To help make backing out of a parking space safer, the AMG SL has standard Rear Cross-Traffic Alert and Rear Cross Traffic Brake automatically engages the brakes to help avoid a collision. Porsche charges extra for Rear Cross Traffic Alert on the 911.
The AMG SL’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 911 doesn’t offer a driver alert monitor.
Both the AMG SL and the 911 have standard driver and passenger frontal airbags, front side-impact airbags, side-impact head airbags, four-wheel antilock brakes, traction control, electronic stability systems to prevent skidding, daytime running lights, rearview cameras and available lane departure warning systems.