Children in Seatbelts Question

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MSI
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Children in Seatbelts Question

Post by MSI »

(from another forum, but our own Stan McHenry answered so reposting here!)
Q: For those who have investigated crashes where small children were in seatbelts, not a child seat. Do you see the seatbelts locked, or have you seen them retract with no evidence that they had been worn? These are children who are required to be in a safety seat recommended for their size, but were not. Just sitting on the regular seat, with a seatbelt on.

A: My name is Stan McHenry , a 30 year career police officer, 20 years of which were spent assigned to a tactical traffic unit that specialized in the investigation of and reconstruction of fatal and other serious motor vehicle crashes. I am also a Safe Kids Worldwide certified Child Passenger Safety Technician Instructor, having held that status since 1999.
Post crash seatbelt retractors being locked is fairly common and often aids in determining pre-crash use particular to specific seating positions. The absence of seat belt burn could be a matter of several factors including speed, weight of occupant, proper use of restraint system and delta-v.
What peaks my interest here is whether or not the lap/shoulder belt was being worn properly at the moment of impact?
From my experience as a police officer as well as a child passenger safety advocate, I know that at this age (10+), depending primarily on the height of the child, it is not uncommon for the child to place the shoulder portion of the lap/shoulder belt system either under their arm or behind their back which would obviously alter the loading and thereby the effectiveness of restraint system. Of particular concern would be if the shoulder portion was worn behind the child’s back. In this scenario, the injury exposure is tremendous with the lap portion only having to restrain the child, seriously exposing lower C-spine, liver, spleen and intestines in a combination of injuries known as Seat Belt Syndrome.
Another effect, if this were to be the case, would be the exposed portion of the lap/shoulder, (beyond the retractor) would be significantly shorter than would be expected as the shoulder belt runs from the latch plate up the child’s back rather than around the child’s lower torso, across the chest, over the shoulder and back to the retractor.
Hope this helps…
MSI
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Joined: Thu Jun 18, 2009 12:37 pm

Re: Children in Seatbelts Question

Post by MSI »

A followup question came in and here's Stan's response: (I don't post the question since don't have their permission to post)
Q: The car with 2 small children in the back impacted a stopped vehicle at about 50+ mph. There was airbag deployment. There were no child safety seats and the seat belts were in the retracted position. I'm trying to find out from other recons/experts if there is any likelihood that the seat belts were being worn, but due to the small size and weight of the occupants they did not lock-out during the impact.

A: A couple of questions immediately come to mind. Are the weights of the children know at the time of the event? Also, what time if day did this event occur?
The first question would answer the loading of the retractor(s) and the second addresses whether or not they were likely to be asleep? At 5 and 6 years of age, they were clearly too physiologically small to be without a booster seat at the very least. At that age there is also a concern that there would likely be a behavioral issue with regard to continued proper use of particularly the shoulder portion of the lap/shoulder system.
It is relatively easy to “switch” any retractor by simply pulling the shoulder portion of the belt away from the D-ring rapidly. This will cause the retractor to “lock” and so long as the pressure that caused it to lock remains, the retractor stays locked. If the retractor type is switchable, by far the most common, relieving the pressure that caused the retractor to lock in the first place, causes the retractor to go back to the “emergency” mode where the retractor will allow for some motion forward and back. However, a sudden change in direction or acceleration or deceleration in any direction (emergency) will cause the retractor to again switch the the locked mode. The other type of retractor likely to be found on a current model car is an emergency locking retractor. With this system, the latch plate, the part that goes into the buckle, possesses the locking feature. The retractor is and remains in the emergency mode and will lock under the same conditions as the switchable retractor in the emergency mode.
If you know the year, make and model of the vehicle it would be easy to determine which system you are dealing with.

Stan McHenry
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