Sunday, September 19, 2010

The Risky Ride of the 15-passenger van: A history

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Flawed design

Fifteen-passenger vans have three primary safety problems .

The vans are:

• unstable when loaded with 10 or more passengers, leading to a significant increase in the risk of rollover crashes.

• difficult to handle under fully loaded conditions because they are susceptible to oversteer in emergency maneuvers, which leads to loss of control.

• designed so excess weight is loaded on the back left tire, increasing the likelihood of tire failure and accidents. According to the National Highway Traffic Safety Administration (NHTSA), “belt-leaving-belt tread separations, whether or not accompanied by a loss of air from the tire, reduce the ability of a driver to control the vehicle, particularly when the failure occurs on a rear tire and at high speeds. Such a loss of control can lead to a crash.”12

The trouble began in the 1960s, when Ford designed the Econoline E-350 Super Club Wagon as a cargo-only vehicle. When other manufacturers began selling passenger vans in the 1970s, Ford spotted a niche in the market. The automaker introduced its first passenger van in 1975. It began selling the 15-passenger version of the E-350 in 1979, and the vehicle has remained essentially unchanged since then.

When designing the van, Ford considered building a completely different vehicle. Design considerations included an increased wheelbase, dual rear wheels, and lower ride height. Instead of incorporating these elements, however, Ford simply added another 20 inches to the back of the Econoline cargo van for another bench seat. This increased the passenger load capacity to 15 and put additional rear overhang and potential load behind the rear axle, moving the van’s center of gravity upward and rearward. This created a number of safety problems, the primary one being an increased propensity to roll over.

Ford documents indicate that its engineers considered various alternative designs that would have been superior to the quick-and-easy approach the automaker eventually adopted.13 The engineers went so far as to recommend that design changes be studied further. But Ford management decided that the cost of implementing the design changes outweighed the benefits and deferred them for future consideration. To this day, the changes have not been implemented.

Chrysler’s 15-passenger van—the Ram 3500—arrived on the market before Ford’s and also remained essentially unchanged since the 1970s until the automaker stopped manufacturing it in June 2002. Under fully loaded conditions equal to the van’s gross vehicle weight, the left rear tire is overloaded because most of the passenger and luggage weight is distributed to the left rear part of the van. As tire manufacturers claim in almost every tire-defect case, overloaded tires are a common cause of tire failure. The left rear tires on Chrysler vans are overloaded when the vehicles are used as marketed and, therefore, are more susceptible to failure, which can lead to catastrophic crashes.

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