Feature: When safety belts may do more harm than good
Hybrid 3 crash test dummies with abdominal insert. Click image to enlarge
Review and photos by Bob McHugh
"One of the problems of this type of injury is that the child may seem fine right after the crash, yet they may have a liver laceration or they have a perforated intestine," said Dr. Steve Rouhana. "These things may not show up until a day or two later, at which time it could be an extremely serious injury and possibly fatal."
We were discussing a fairly common type of injury that a child, particularly in the four to eight-year age range, can sustain in a motor vehicle collision. Known as "submarining", it's when the seat belt goes over the pelvis and up into the soft abdominal area.
Dr. Rouhana is the senior technical leader with Ford's Passive Safety Research and Advanced Engineering Department. Three or four years ago, he was approached by a colleague, at the Children's Hospital of Philadelphia, about an alarming statistic in her research.
She had looked at children who are restrained in automobile collisions and had found that in those between four and eight years old there was a 25-fold increase in the risk of abdominal injuries, if the children were not restrained in booster seats.
"The current child crash test dummy, the Hybrid3 six-year old, has no abdominal injury capabilities," said Dr. Rouhana. "It can't tell whether a belt is in the abdomen and can't give you a risk of injury if the belt is there. So it makes it difficult for us as automotive manufacturers to develop restraint systems for kids."
Dr. Steve Rouhana. Click image to enlarge
Ford has developed the more lifelike abdomen insert for the Hybrid3 crash test dummy in conjunction with STR Systems, The Children's Hospital of Philadelphia, Wayne State University, the University of Virginia and the Takata Corporation.
The prototype pediatric abdomen insert is similar in size and shape to that of a 6-year-old child and is made of multiple layers of liquid silicone that, when solidified, forms a tough silicone shell. Inside is a set of electrodes immersed in a conductive fluid that comprise the sensors for the abdomen: six electrodes at the front of the abdomen and one reference electrode at the back.
The new insert will require some modifications to the current dummy and Ford is also working with the University of Michigan, which is developing a new pelvis for the dummy. "Both of these are important in order to have the right interaction of the seatbelt with the dummy," said Dr. Rouhana, "so together, we have been testing this abdomen and pelvis system."
In February they got the approval of the SAE (Society of Automobile Engineers) committee, which oversees the Hybrid3 dummy family and governs any changes, to do a round-robin test series as an independent evaluation.
This Fall, the first prototypes should be ready and Ford will start an international test program with other auto manufacturers and government bodies, including Transport Canada. "It's our hope that the whole auto industry will use this new dummy, when we get the final buy-in from the SAE," said Dr. Rouhana.
Hybrid 3 crash test dummy with abdominal insert. Click image to enlarge
The goal of this research is to provide a tool that auto manufacturers and child seat manufacturers can use to improve their products. "It may not be possible to develop a seat belt that can safely restrain a 250 lb. adult and a 50 lb. child,' said Dr. Rouhana. "So it's possible we will always need booster seats."
In British Columbia, new mandatory booster seat legislation took effect on July 1, 2008. Booster seat usage starts when your child weighs more than 18 kg (40 lb.) and has outgrown a forward-facing child safety seat. It's required, by law, to be used until your child reaches nine years of age, unless they have reached the height of 145 cm (4' 9") tall.
"My kids were in booster seats until they were eleven years old, because they didn't fit in the adult belt system," said Dr. Rouhana.
When a child is moved out of a child seat into an adult belt system, typically the vehicle seat cushion is too long for their legs. "They scoot their bottom forward until their knees will bend around the seat, as it's uncomfortable to sit with your legs straight out in a vehicle for a long time," said Dr. Rouhana. "This tilts their pelvis rearward and it's their pelvis that we are trying to hold onto with the lap belt. The pelvis is a strong bone that can take the forces of a crash, much better than the abdomen can."
There are a number of tests that parents can do to see if their child is ready to be out of a booster seat. There's a wealth of information available on internet web sites that deal with child safety, and your vehicle's owner's manual has info as well. However, Dr. Rouhana did stress two simple checks: First, can the child sit in the vehicle seat with his bottom all the way back and bend his knees around the seat cushion? And, does the vehicle's shoulder belt fit between the neck and the shoulder? It shouldn't be on the face or neck.
"Crashes occur and ten children die every month in vehicle crashes in Canada," said Dr. Rouhana. "Our children are our future, and even though it's sometimes hard to balance all the things that are going on these days, they should be our top priority, so take that extra minute."
A shorter version of this article was first published in the Vancouver Province newspaper where Bob McHugh writes a weekly column on behalf of the British Columbia Automobile Association.
