The 4 Series Convertible’s pre-crash front seatbelts will tighten automatically in the event the vehicle detects an impending crash, improving protection against injury significantly. The TT doesn’t offer pre-crash pretensioners.
The 4 Series Convertible has standard front and rear seat tall, head-protecting side-impact airbags, which act as a forgiving barrier between the passengers and the door. Combined with high-strength steel door beams this system increases protection from broadside collisions. The TT doesn't offer rear-seat side-impact airbags, only ones for front seat occupants.
The 4 Series Convertible has standard City Collision Mitigation, which use forward mounted sensors to warn the driver of a possible collision ahead. If the driver doesn’t react and the system determines a collision is imminent, it automatically applies the brakes at full-force in order to reduce the force of the crash or avoid it altogether. The TT doesn't offer collision warning or crash mitigation brakes.
Over 200 people are killed each year when backed over by motor vehicles. The 4 Series Convertible M440i offers an optional 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 TT doesn’t offer backup collision prevention brakes.
The 4 Series Convertible’s 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. The TT doesn’t offer a lane departure warning system.
The 4 Series Convertible M440i offers an optional Surround View to allow the driver to see objects all around the vehicle on a screen. The TT 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.
To help make backing out of a parking space safer, the 4 Series Convertible’s standard Cross Traffic Warning uses sensors in the rear to alert the driver to vehicles approaching from the side, helping the driver avoid collisions. The TT doesn’t offer a rear cross-path warning system.
The 4 Series Convertible’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 TT doesn’t offer a driver alert monitor.
Both the 4 Series Convertible and the TT have standard driver and passenger frontal airbags, front side-impact airbags, driver and front passenger knee airbags, side-impact head airbags, front and rear seatbelt pretensioners, four-wheel antilock brakes, traction control, electronic stability systems to prevent skidding, post-collision automatic braking systems, daytime running lights, blind spot warning systems, rearview cameras and available all wheel drive.
The BMW 4 Series Convertible weighs 523 to 1095 pounds more than the Audi TT. The NHTSA advises that heavier cars are much safer in collisions than their significantly lighter counterparts.