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 3 Series Sedan are reminded to check the back seat if they opened the rear door before starting out. The IS doesn’t offer a back seat reminder.
The 3 Series Sedan has standard Active Head Restraints, which use a specially designed headrest to protect the driver and front passenger from whiplash. During a rear-end collision, the Active Head Restraints system moves the headrests forward to prevent neck and spine injuries. The IS doesn’t offer a whiplash protection system.
The 3 Series Sedan’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 IS doesn’t offer a driver alert monitor.
Both the 3 Series Sedan and the IS 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, post-collision automatic braking systems, daytime running lights, rearview cameras, available all wheel drive, lane departure warning systems, blind spot warning systems, around view monitors and rear cross-path warning.
The National Highway Traffic Safety Administration does 35 MPH front crash tests on new vehicles. In this test, results indicate that the BMW 3 Series Sedan is safer than the Lexus IS:
| 
 | 3 Series Sedan | IS | 
| OVERALL STARS | 5 Stars | 4 Stars | 
| 
 | Driver | |
| STARS | 5 Stars | 4 Stars | 
| HIC | 145 | 220 | 
| Neck Injury Risk | 23% | 35% | 
| Neck Stress | 207 lbs. | 429 lbs. | 
| Neck Compression | 32 lbs. | 60 lbs. | 
| Leg Forces (l/r) | 201/230 lbs. | 599/675 lbs. | 
| 
 | Passenger | |
| STARS | 5 Stars | 4 Stars | 
| HIC | 252 | 282 | 
| Neck Injury Risk | 33% | 41% | 
| Neck Compression | 74 lbs. | 81 lbs. | 
| Leg Forces (l/r) | 200/338 lbs. | 399/459 lbs. | 
New test not comparable to pre-2011 test results. More stars = Better. Lower test results = Better.
The National Highway Traffic Safety Administration does side impact tests on new vehicles. In this test, which crashes the vehicle into a flat barrier at 38.5 MPH and into a post at 20 MPH, results indicate that the BMW 3 Series Sedan is safer than the Lexus IS:
| 
 | 3 Series Sedan | IS | 
| 
 | Front Seat | |
| STARS | 5 Stars | 5 Stars | 
| HIC | 107 | 142 | 
| Chest Movement | .8 inches | 1 inches | 
| Abdominal Force | 179 lbs. | 203 lbs. | 
| Hip Force | 252 lbs. | 406 lbs. | 
| 
 | Into Pole | |
| STARS | 5 Stars | 5 Stars | 
| Max Damage Depth | 13 inches | 15 inches | 
| HIC | 270 | 293 | 
| Hip Force | 544 lbs. | 650 lbs. | 
New test not comparable to pre-2011 test results. More stars = Better. Lower test results = Better.

