IIHS Rollover Test and Pickup Safety


Ever wonder why one pickup truck costs more to insure than another of equal performance? Reasons are myriad, and the driver is by far the biggest variable, so the Insurance Institute for Highway Safety does objective testing that eliminates the driver and focuses on vehicle behavior in a crash. (It is developing tests to determine how well vehicles can avoid a crash, testing safety features like stability control, lane departure and blind spot warnings, collision mitigation braking and so on.)

The IIHS roof crush test is an important thing to look at when assessing a vehicle's safety prior to purchase. The test assigns a rating for a vehicle's occupant protection in a crash involving a rollover. According to IIHS' most recent data (), pickups have some of the highest fatality rates in solo rollover accidents. Categorized by vehicle type and size, minivans were the safest while "very large" (heavy-duty crew cabs) four-wheel-drive pickups were the worst. Small two-wheel-drive, large two- and four-wheel-drive and very large two-wheel-drive pickups filled out the top five vehicle types with the highest fatalities in single rollover crashes. Although they top the list, IIHS does not test HD pickups and has no plans to do so.

The rollover test involves a steel plate pressed at a constant speed against the roof/door line at approximately 30 degrees from horizontal. Force applied to the plate is measured as the roof is crushed 5 inches; peak force typically occurs around 2.5 inches of deflection just before a side window or windshield breaks. The peak force is divided by the vehicle weight that IIHS records with "typical engine, transmission and equipment options," and the resulting numerical value corresponds to a word grade: a Good rating means peak force divided by vehicle weight (IIHS "strength-to-weight ratio") is 4.0 or greater; Acceptable is 3.25 to 4; Marginal is 2.5 to 3.25; Poor is anything less than 2.5. The test hasn't changed for 40 years, although until 2013 the federal strength-to-weight requirement was only 1.5. It's been strengthened and is being phased in for 2013 models.

IIHS did test some recent (2004 to 2013 models) full-size pickups. Of these, crew cab versions of the Ford F-150, Toyota Tundra and Honda Ridgeline scored Good. The Nissan Titan received an Acceptable rating, and the Chevrolet Silverado 1500, GMC Sierra 1500 and Ram 1500 were rated Marginal.

An IIHS footnote about the Titan crew cab raises two issues. The IIHS states: "Rating applies only to crew cab models, except for 4wd Crew Cab long bed model. Rating of this model is Marginal." First, most of the vehicles tested were two-wheel drive and the majority of pickups sold are four-wheel drive. That means most pickups on the road do not fall in the "typical equipment" tested by the IIHS. Secondly, weight is critical to this rating system, so you might consider doing your own math.

If you use the peak force measured during the test and calculate with the gross vehicle weight rather than empty, it is possible the same truck would get a lower rating. Yes, payload is often ejected in a rollover but things like hitches, tool boxes, fuel tanks and secured cargo often stay in the truck — and five adults often account for a big portion of payload on crew cabs; that weight would drop some pickups one rank. Likewise, if a vehicle has shed some weight — say no spare and rear bumper, or a lighter flatbed, that could bump it up one rank.

Unless the frame rails are bending we don't believe the actual roof crush dynamics of the Titan crew cab differ if it has front drive or a longer bed; it's merely the added weight that changes the label from Acceptable to Marginal. The Titan's sister vehicle, the Armada SUV, hasn't been crushed by IIHS but has a zero rollover fatality rate, and Nissan's Frontier is the only compact pickup IIHS tested that scored a Good (for 2005-2013 model years).

Regardless of rank, the new standards likely spell the demise of an extended cab without a center pillar — simple physics says a span with three supports will be stronger than one with two. Beyond noise and vibration issues there are downsides to having a 25-square-foot aperture in the side of a pickup cab, and those are only part of why the new Silverado and Sierra 1500s use a B-post double cab.

The IIHS tests can help you determine which pickup has the most crush-resistant roof. However, that's just one aspect of a truck's safety. The other IIHS crash tests and whether a pickup is equipped with electronic stability control are other important factors. ESC was required in all new passenger vehicles starting with 2012 models; it helps prevent rollovers. ESC saves lives and reduces insurance losses, the IIHS says, but its benefits vary from vehicle to vehicle. IIHS hopes to get a better understanding of this variance through more testing.

Ultimately, the safest pickup truck is the one you avoid rolling in the first place and in which you're properly belted for when you can't avoid an accident.


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