From The Ergoweb® Learning Center

Ergonomics and a Deadly Ride on the “Perilous Plunge”

A recent Associated Press (AP) news article describes the events surrounding a woman’s death at Knott’s Berry Farm, an amusement park in California, USA. According to the article, 40-year-old Lori Mason-Larez, who weighed nearly 300 pounds, fell to her death from the “Perilous Plunge” water ride. Ergonomics, it appears, played a significant role in the accident.

The AP article does not mention ergonomics, but it does give an overview of the competing accident theories emerging in a lawsuit filed by Mason-Larez’s family against the amusement park, it’s owner, Cedar Fair LP, and Intamin Ltd, the manufacturer of the ride.

According to the manufacturer, the woman fell from the ride because she was not properly belted, and should not have gotten on the ride if she could not be safely restrained. Marc Feldman, the family’s attorney, claims that abrasions on her thighs indicate that she was belted in before she fell. The coroner reports that Mason-Larez’s abdomen was eight inches larger than the 50-inch seat belt, and investigators speculate that if belted, she may have placed the belt below her abdomen.

I don’t know all the facts surrounding this accident, and I’m relying solely on the AP’s account, so I’m sure there’s more at play than I’ll ever know. Regardless of the details, however, this incident brings up some interesting questions directly related to ergonomics.

The manufacturer believes customers would contest weight or waist-size restrictions, and is quoted by AP as saying, “Basically, we cannot discriminate against anybody.” The family’s attorney, on the other hand, notes that there was a height restriction requiring riders to be at least four feet tall, a line presumably drawn for safety. Is height-based discrimination any different than weight or circumference based discrimination? Is anthropometry (body size) based discrimination fair?

The fact is, ergonomists, engineers, architects and other designers routinely make design decisions that discriminate. We have to, because it is rarely feasible to accommodate all conceivable users. Designers who are not aware of ergonomics principles – and unfortunately there are many – may unintentionally discriminate against a large number of users because they don’t adequately consider human variations in their designs. But even when ergonomics is thoroughly considered it’s typical to design only for a reasonable segment of the expected user population. In the case of anthropometric variations, such as the abdomen dimension at the heart of this case, an ergonomist might recommend accommodating 90% of a population. That is, one could argue, the design would discriminate against 10% of the people.

I won’t speculate who’s at fault – if anyone – in this tragic accident, or what might have been done to avoid it. I will say that design discrimination happens every day, will continue to happen, and should continue to happen. If its informed design, there’s nothing inherently wrong with it, and it’s usually unavoidable. How to reduce risk after a design is complete, such as user and use restrictions, training, warnings, etc., is another subject directly impacted by ergonomics, but beyond the scope of this article.

The real issue in this case seems to be a social one. Apparently, it’s socially acceptable to discriminate with respect to height, but not with respect to girth. And in the end, I suppose it depends on which side of the line you fall.