Investigative Mommy Blogger published their first report this week, and it's a good read on an interesting issue. The report's authors found that for kids between one month and five years of age, shopping carts result in more emergency room visits than strollers, high chairs, cribs, changing tables, walkers and jumpers, baby gates, and bouncy seats combined, or more than 23,000 times in 2007 alone. The question is, why?

We all know not to do this:


Photo by greefus groinks

and we are all well aware that one should never, under any circumstances, be caught doing this:


Photo by Nathan Huth

Certainly many of those 24,000+ injuries can be attributed to kids riding in the basket, jumping out, hanging on the side or front, and otherwise bringing those "do not" signs to life as a harried parent tries to get through the store without a tantrum. But "many" is a fuzzy statement. How many?

IMB focuses on the role of safety belts in this issue, and rightly so. Kids who are strapped in find it very difficult to fall out of shopping carts, try as they might. Their blogging team sent fourteen bloggers visited a total of 30 stores to check shopping carts and found that a total of one third of them had broken or missing safety belts. This is pretty poor performance considering the various rules that mandate scheduled upkeep and outline other retailer responsibilities.

Then again, if you're a parent who shops with a young child, I'd be surprised if this number seemed high to you. I bet you could quickly compile a list in your mind of which stores you visit that have a high number of broken straps.

But while most parents will reject a gunky cart because they don't want that gunk going in the kiddo's mouth, many shrug off a broken safety belt because there's a false sense of security. You're three inches from the child's seat when you're making that snap decision, and it's easy to forget how frequently we may take a step or two away from the cart, for several mentally involved seconds at a time, while we pore over ingredient labels or competing deals.

If your interest lies simply in knowing how to help your child survive the dangers of shopping carts, we can sum it up quite simply:

• Make your child sit in the child seat. No exceptions.


• Only use a shopping cart with a working safety belt.


• Don't leave the cart to get something - take the cart with you.


• Don't lean on the cart handle.

There! You didn't need us for that, did you? You already knew it, and that 24,000+ figure is a helpful memory-booster.

But what if thousands of kids properly buckled in their shopping cart seats are still heading to the ER?

Investigative Mommy Blogger's excellent report, in addition to demonstrating a cooperative model for semi-professional consumer research and advocacy, offers plenty of data for the rest of us to chew on.

Which brings me to the small but very flavorful bite I'd like to take out of this issue: A significant percentage of these injuries, if the AAP interpretation is sound, don't have much to do with safety belts.

Stroller Shopping cart physics

Parsing out the causes of shopping cart accidents is difficult because the numbers - both those IMB cites from the Consumer Product Safety Commission (CPSC) and those in the American Academy of Pediatrics 2005 survey that IMB cites, which we looked at - leave some questions unanswered. The AAP says that 38% of injuries to kids age two and under (using 2005 numbers) were associated with cart tip-overs, which are often contributed to by the child's vertical position and where their center of gravity falls. Regular readers will remember Adrienne's recent discussion of stroller physics; it's time to put that knowledge to use. Read what the AAP has to say about shopping cart design:

Shopping carts vary significantly in design characteristics including height, weight, center of gravity, and wheelbase dimensions. Some carts have a relatively narrow wheelbase in relation to their height, which makes them more likely to tip over [sideways]. An important variable affecting rearward tip-over potential is the location of the handle and child seating area in relation to the rear axle. If a vertical line is dropped from the handle, the horizontal distance between that line and the rear axle can vary significantly. The greater this horizontal distance, the more likely downward pressure on the handle will cause the cart to tip over backward. A vertical force as little as 16 lb applied downward on the handle is all that is required to tip some carts over An average adult can apply this amount of force without difficulty with forearms resting on the top of the cart handle. In addition, if the child seating area is located farther rearward in relation to the rear axle of the cart, or if the child in the seating area leans toward the rear of the cart, the cart will more easily tip over backward.

You can download the five-page technical report, "Shopping Cart-Related Injuries to Children," in PDF format.

Now, let's work those armchair engineering degrees to work, shall we? For this exercise, we'll focus on "rearward tipping."

This is what most of us would consider a typical shopping cart, with a deep wedge that serves as a leg-dangling area for a child and a rear axle that thrusts back out to place the child's center of gravity under the cart rather than behind it:


Photo by Kasia/flickr.


Photo by Rick Harris.

But not all carts are like that, right? We'll start off with the simplest counterexample.

When viewing the below photograph, please keep in mind that we quite consciously avoid using publicly-shared photographs as examples of bad behavior. (This makes it very hard to find graphics to use in our car seat reporting, because most children in or being placed in car seats on Flickr - from infants through booster seat users - are not using them properly, for one reason or another. Ninety percent, easy.) So I am not employing the below photo to condemn parents who let their children sit in shopping carts eating hot dogs.


Photo by hive.

Because this cart features a straight vertical drop from where the handle attaches to the basket down to the rear axle, it's easy to measure, as the AAP put it, the "location of the handle and child seating area in relation to the rear axle" - it's the distance from the handgrip to the basket, just a few inches. But the legs of a child properly seated in this cart would also be outside the wheelbase, as would any other part that might project out over the handle (drawing, leaning forward to reach for a parent or an object in front of them, etc.). This decreases the amount of pressure a parent would have to put on the cart handle to tip it backward, and if this were done quickly - in conjunction, say, with the child increasing the weight they bear forward through their own movement - it becomes easier to imagine how these incidents occur.

This one looks to have an unusual amount of potential weight positioned outside of the wheelbase, although the angle of the photograph makes it a bit difficult to measure.


Photo by Caveman 92223.

This last one is the worst of the lot, and was undoubtedly decommissioned by a shopping cart designer turned masked vigilante. See how far back the handle extends from the horizontal position of the rear wheels?


Photo by Editor B.

Now imagine any of these carts with an infant car carrier strapped, balanced, or otherwise positioned in the cart's child seat. That changes everything again, doesn't it?

When it comes to child safety, not all shopping carts are created equal. The kinds with large plastic seating areas - a section with multiple belted seats positioned lower to the ground, between the basket and the handle, or the play vehicles where kids sit below the basket itself - have been, in part, a response by manufacturers to the tip-over problem - lowering kids' center of gravity and getting them firmly inside the wheelbase, as well as allowing for the safer belting of older children. But if the problem with standard shopping carts is one of simple physics, why not just have regulations mandating certain angles or limits on how far the basket can project out on a standard-issue shopping cart?

That's a question for the CPSC, says the AAP.

The CPSC denied petitions to promulgate mandatory standards for shopping carts in 1975, automatic child restraints in carts in 1994, and preventing cart tip-overs in 1998. At the time the petition was denied in 1975, the industry indicated that it would pursue development of a voluntary standard for shopping carts, but no action was taken until 2002. Thomas H. Moore, 1 of 3 CPSC commissioners who reviewed the petition in 1998 requesting a performance standard to prevent shopping cart tip-overs, indicated in a written minority opinion that he favored deferring a decision on the petition and pursuing a voluntary standard with the industry. The CPSC engineering staff stated at that time that it would be "a relatively straightforward matter" to develop a performance standard for shopping cart stability. However, the other 2 commissioners did not agree with Moore, and the petition was denied. In 1995, an industry spokesman articulated the view that "injuries involving shopping carts are due to consumer misuse of the product and are not flaws in the current design or a lack of safety mechanism." In September 2002, American Society for Testing and Materials (ASTM) International formed Subcommittee F15.56 on Shopping Carts to develop a voluntary standard for shopping carts. The Standard Consumer Safety Performance Specification for Shopping Carts F2372-04 was published in July 2004.

However, unlike the standards in 21 other countries, the ASTM standard does not address shopping cart stability. Stating that there were "not sufficient frequencies and severity of ‘tip-over’ injuries, relating to the cart’s stability, to warrant requirements and testing for 'tipover,'" the ASTM subcommittee voted to overrule the negative vote of the American Academy of Pediatrics (AAP) against the draft standard and the recommendation of the AAP that a stability performance standard and test procedure be included in the shopping cart standard.

If you haven't read it yet, you should hop on over to Investigative Mommy Blogger and check out their great reporting on shopping cart safety, which includes injury stories from moms, interviews with representatives from the CPSC and the AAP, and more. We can't wait to read more reports from Kelby Carr's team.