The XM’s pre-crash front seatbelts will tighten automatically in the event the vehicle detects an impending crash, improving protection against injury significantly. The Cayenne Coupe doesn’t offer pre-crash pretensioners.
In the past twenty years hundreds of infants and young children have died after being left in vehicles, usually by accident. When turning the vehicle off, drivers of the XM are reminded to check the back seat if they opened the rear door before starting out. The Cayenne Coupe doesn’t offer a back seat reminder.
Over 200 people are killed each year when backed over by motor vehicles. The XM has a standard Active Park Distance Control that uses rear sensors to monitor for objects to the rear and automatically applies the brakes to prevent a collision. The Cayenne Coupe doesn’t offer backup collision prevention brakes.
The XM’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 Cayenne Coupe.
The XM 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 and moves the vehicle back into its lane. A system to reveal vehicles in the Cayenne Coupe’s blind spot costs extra.
To help make backing out of a parking space safer, the XM’s standard Cross Traffic Warning with braking function uses sensors in the rear to alert the driver to vehicles approaching from the side and automatically engage the brakes. The Cayenne Coupe doesn’t offer a rear cross-path warning system.
The XM’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 Cayenne Coupe doesn’t offer a driver alert monitor.
Both the XM and the Cayenne Coupe have standard driver and passenger frontal airbags, front side-impact airbags, driver and front passenger knee airbags, side-impact head airbags, 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 and rearview cameras.
The BMW XM weighs 421 to 1431 pounds more than the Porsche Cayenne Coupe. The NHTSA advises that heavier vehicles are much safer in collisions than their significantly lighter counterparts.