The i4’s pre-crash front seatbelts will tighten automatically in the event the vehicle detects an impending crash, improving protection against injury significantly. The Prius Prime doesn’t offer pre-crash pretensioners.
The BMW i4 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 Prius Prime doesn’t offer a front passenger side knee airbag.
The i4 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 Prius Prime 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.
The i4 M50 has all-wheel drive to maximize traction under poor conditions, especially in ice and snow. The Prius Prime doesn’t offer all-wheel drive.
The i4 offers an optional Surround View to allow the driver to see objects all around the vehicle on a screen. The Prius Prime only offers a rear monitor and front and rear parking sensors that beep or flash a light. That doesn’t help with obstacles to the sides.
The i4 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. Only the Prius Prime Limited offers a blind spot warning system.
To help make backing out of a parking space safer, the i4 has standard Cross Traffic Warning, helping the driver avoid collisions. Only the Prius Prime Limited offers rear cross-path warning.
Both the i4 and the Prius Prime 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, daytime running lights, lane departure warning systems, rearview cameras and driver alert monitors.
The BMW i4 weighs 1290 to 1653 pounds more than the Toyota Prius Prime. The NHTSA advises that heavier cars are much safer in collisions than their significantly lighter counterparts.