The iX’s pre-crash front seatbelts will tighten automatically in the event the vehicle detects an impending crash, improving protection against injury significantly. The RDX doesn’t offer pre-crash pretensioners.
Both the iX and RDX have child safety locks to prevent children from opening the rear doors. The iX has power child safety locks, allowing the driver to activate and deactivate them from the driver's seat and to know when they're engaged. The RDX’s child locks have to be individually engaged at each rear door with a manual switch. The driver can’t know the status of the locks without opening the doors and checking them.
The iX’s standard pretensioning seatbelts also sense rear collisions and remove slack from the front seatbelts to help protect the occupants from whiplash and other injuries. The RDX doesn’t offer a whiplash protection system.
The iX has a standard PostCrash iBrake, which automatically applies the brakes in the event of a crash to help prevent secondary collisions and prevent further injuries. The RDX 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 iX 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 RDX doesn’t offer backup collision prevention brakes.
To provide maximum traction and stability on all roads, Full-Time Four-Wheel Drive is standard on the iX. But it costs extra on the RDX.
Both the iX and RDX have rear cross-traffic warning, but the iX has Cross Traffic Warning with braking function (automatically applies the brakes) to better prevent a collision when backing near traffic. The RDX’s Rear Cross Traffic Monitor doesn’t automatically brake.
The iX’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 RDX doesn’t offer a driver alert monitor.
Both the iX and the RDX 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, crash mitigating brakes, daytime running lights, lane departure warning systems, blind spot warning systems, rearview cameras, rear cross-path warning and available around view monitors.
The BMW iX weighs 1601 to 1994 pounds more than the Acura RDX. The NHTSA advises that heavier vehicles are much safer in collisions than their significantly lighter counterparts.