The car had a front passenger and two rear seat passengers, one right and one left. In the middle rear seat there was a tray of cupcakes weighing ~2lbs. As we were driving at night in a complex area of freeway onramps and offramps an alarm started to deploy, beaping steadily. I glanced down at the multi-info-display (MID) and couldn't tell what the alarm was, and I was driving at around 55-60mph, at night. Over the next 45 seconds or so the alarm increased in frequency to the point of starting to sound outright urgent. I finally saw noticed three tiny icons in the lower right part of the MID, amidst an array of other lit icons and indicators, representing the 3 rear seats, and the center one was not illuminated. The car's sensing system apparently determined the seat was occupied but the occupant not belted in. I told everyone to check seatbelts. By now everyone in the car was in a state of near panic as all belts were secured. At the last few seconds, distracted by the urgency of this alarm and trying ascertain what the heck it was, I nearly struck traffic cones and had to swerve to miss them. Thank fate as I swerved to get back into my lane (cones were cordening off a whole lane which I was heading into) and didn't run into another vehicle--it easily could have resulted in a crash. I visited a car owner forum and here is a comment from another owner, "...Toyota doesn't need to have such an obnoxious seatbelt warning system -- even just for the front-seat occupants -- in which the sound gets louder and louder and louder; it's about the worst I've seen in any brand...." Other seatbelt alarms in my experience sound, then stop, then restart, but never escalate like this one. The combination of an atypical satbelt alarm that escalates to the point of urgency, combined w/ a hypersensitive seat occupant sensor confirmed by others, difficult to focus on while driving alarm icons, makes this design potentially disastrous as my story suggests.

- Arvada, CO, USA