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Shopping Carts
Ryan Engineering

Shopping Carts Can be a Danger to Children
  (vol.98 Issue 1) by John Morse, PhD

The Consumer Product Safety Commission reports that in 1991, there were 25,500 children injured by shopping carts that required emergency room treatment! By 1992, that number had risen to 26,700. A sizable percentage of these injuries are from cart tip-over. The CPSC estimates that 1 out of every 2,000 children will be injured in a shopping cart tip-over accident before reaching age 6. This is an injury that will require treatment in an emergency room. A rear tip-over, for instance, normally results in a broken femur or worse.

Ryan Engineering has performed testing on a number of shopping carts. We placed a simulated 29 pound child in the child seat and measured the amount of force on the handle necessary to tip the cart over backward. These amounts were shockingly low for some models of shopping carts.

Carts can be tipped over by pulling straight downward on the handle, and they can be tipped over by pulling downward and backward at the same time.

These forces happen when older children hang or yank downward on the handle or when someone trips or when someone pulls backwards momentarily as the rear wheels run over an obstruction as small as 1/16th inch high. Also adults often lean on shopping cart handles. For unstable shopping carts, as little as 75 pounds straight downward can cause the cart to flip backwards. For a stable shopping cart, the downward force can range over 3000 pounds.

The combination of a rearward pull in the horizontal direction plus a downward force happens frequently in shopping cart use. Imagine a child hanging onto the handle while leaning backwards or an adult resting his arm on the handle at an angle. As an example, if the combination of the horizontal and vertical forces make an angle that is 20 degrees off the vertical in the rearward direction, the tip-over force ranges from 31 to 99 pounds.

Ryan Engineering has found the design differences between these carts to be based on aesthetics, rather than utility, function, or price. Therefore, a cart that is easily tipped over has no engineering basis for its unsafe design.



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