Rollover Crashes, Testing and Ratings

Prior to 2000, before Electronic Stability Control (ESC) one-third of all LTV fatalities occurred in rollovers. LTV's are much more likely to roll over than passenger cars because of their higher CG. SUV's have the highest rollover rate and rollover fatality rate. Large trucks are probably most vulnerable to rollover because of their relatively high CG, particularly when loaded. Experienced professional drivers are well aware of their potential instability.

Most rollovers occur when a driver loses control of a vehicle, and it begins to slide sideways. When this happens, something can cause the vehicle to “trip” and cause it to roll over. A few explanations could be a curb, guardrail, tree stump, or soft or no shoulder on the side of the road. When the driver tries to turn a vehicle too forcefully and at a high rate of speed or with a tight turning radius, frictional force between the tires and road surface can cause the vehicle to tip up and then roll over. Many rollovers are single-vehicle crashes. A collision may precipitate a rollover by initiating the rolling motion too fast or causing the vehicles to be redirected sideways, such as in a t-bone.

Roof crush in rollovers is caused by weak roof pillars and windshield header that are not strong enough to hold up the weight of the vehicle as it hits the ground, so it intrudes into the occupant space. In rollovers, roof crush causes side window failures creating ejection portals for occupants to be thrown from the vehicle. The largest number of casualties in rollovers is from ejection. Roof crush also causes a significant number of head and neck injuries, typically the most severe consequences of rollovers.

NHTSA Defines the Scope and Purpose of the FMVSS 216 Roof Crush Resistance Compliance Test:

  • Scope: This standard establishes strength requirements for the passenger compartment roof.

  • Purpose: The purpose of this standard is to reduce deaths and injuries due to the crushing of the roof into the occupant compartment in rollover crashes.

The U.S., European and Australian NCAP and the IIHS produce ratings of new vehicle performance based on dynamic crash tests in frontal, side and rear crashes, and vehicle handling tests. No dynamic-based crashworthiness ratings exist to date for new vehicle performance based on rollover crashes. There is no rating for rollover occupant protection, a crash mode responsible for one-third of all light vehicle occupant fatalities. NHTSA has upgraded the roof crush requirements for new cars, but the time is overdue for an NCAP rating on rollover survivability.

FMVSS 216/216A: Safercar.gov publishes “star ratings” of U.S. vehicles in all accident modes. The rollover ratings are based on an SSF.

The SSF of a vehicle is an at-rest calculation of its rollover resistance based on its most important geometric properties. The SSF is a measure of how top-heavy vehicle is. The SSF only tells you how likely it is for the vehicle to rollover, NOT how well the vehicle structure will hold up if it does roll!

A vehicle's SSF is calculated using the formula SSF = T/2H, where T is the Track Width and H is the Height of the CG. The track width is the distance between the centers of the right and left tires along the axle. The location of the CG is measured in a laboratory represents the height above the ground of the vehicle's mass. The lower the SSF number, the more likely the vehicle is to roll over in a single-vehicle crash.

 

Star Safety Ratings Image

FMVSS 216 Ratings: When evaluating a rating system based solely on FMVSS 216, in comparison to dynamic testing, anomalies abound. The Honda CRV is one such anomaly. The Honda CRV emulates the rollover roof crush performance of vehicles like the Volvo XC-90 and the VW Jetta with a high SWR. The Honda CRV may be a geometry-derived implementation of a roof improvement.

CfIR's research was instrumental in saving lives by providing NHTSA with experimental data and analysis that led to:

  • NHTSA's strengthening of the FMVSS 216 test criteria,

  • NHTSA's adoption of a 2-sided FMVSS 216 test,

  • Design of a more biofidelic prototype rollover crash test dummy neck, and

  • Design of the HALO rollover protection system.

CfIR Developed the Quasi-Static M216 Test and Dynamic JRS Test Fixtures: Rollover testing has been CfIR's primary focus since it was founded by Donald Friedman in 2001. We have conducted quasi-static tests with our M216 device to determine a vehicle's SWR. We developed and utilized the dynamic JRS to evaluate effects of roof crush and restraint systems. We also performed pendulum and spit tests to predict catastrophic injury in a rollover crash.

CfIR Developed the Quasi-Static 2-Sided Roof Strength Fixture (M216): The M216 measures vehicle roof strength similar to FMVSS 216. However, we test both sides of the vehicle roof sequentially at angles that more realistically emulate roof impacts. Our test procedure accounts for the fact that both sides of the roof contact the ground in multiple-roll accidents, and that the second side impact is at a greater roll angle than the first. By measuring roof strength on both sides we are able to quantitatively assess the amount of strength that the bonded windshield contributes to the roof as well as the gross disparity between first side and the second side roof strength (in the first roll of a multiple rollover). The fixture can also be used for glazing retention studies for ejection cases, analysis of roof strength for occupants injured in rear seat seating positions, and for measuring the roof strength of vehicles equipped with ROPS devices.

CfIR Developed the Jordan Rollover System (JRS) 2003: The JRS is a versatile, repeatable rollover testing system capable of assessing vehicle structural design and performance, restraint system performance in rollovers, and rollover occupant kinematics and ejection. A full suite of instrumentation in the test vehicle and on the fixture allow for quantitative analysis of rollover forces and structural performance.The patented dynamic rollover test fixture simulates the rollover impact of a vehicle with a movind road bed. The vehicle is supported by towers at each end and dropped to the road bed for near and far side roof crush forces.

Dynamic of the JRS Rig JRS I Fixture for Dynamic Testing
  • Functionality: The system allows for repeatable tests in which various rollover parameters including pitch, yaw, roll rate, drop height, and contact angle can be altered and controlled. The JRS can also be used to conduct tests on component parts like rollover sensor triggering, side-curtain airbags, pretensioners on belts and spit tests to name a few.

  • Results: The matched pair tests on the JRS clearly demonstrate the reduction in injury potential with a strengthened roof structure. In our most recent tests, the roof intrusion was reduced by approximately 80%. The intrusion velocity was decreased by approxiamtely 50%. With these reductions which can be accomplished by reasonable, engineering alternative designs, the rollover occupant protection is greatly enhanced.

CfIR Developed the Jordan Rollover System (JRS II) 2011: Two improved versions of the JRS have been built for research at the University of New South Wales in Sidney, AU and at UVA in Charlottesville, VA.

CfIR Developed the Nash Carousel 2018: This invention is a device and procedure for testing wheeled vehicles to observe and document a vehicle's dynamic performance and occupant motion prior to and during single or multiple rollovers, assessing the vehicle's occupant restraint system performance - including deployable restraint - triggering - under rollover conditions, and determining the vehicle's occupant compartment integrity and occupant protection performance leading up to and during a rollover. The device of this invention can also be used as a rotating test sled that imparts high levels of longitudinal acceleration and lateral forces on a test object yawing about an orthogonal axis. The device of this investion is superior to current dynamic rollover test devices in that it requires neither that significant parts be removed from the test vehicle nor that any type of frame or carriage be attached to the vehicle. It also can realistically simulate the pre-roll and first roll conditions as applied to a vehicle and its occupants that are typical of actual rollovers.


CfIR Proposes a New Occupant Protection Rating System: We have conducted extensive testing that provides a basis for such a rating. In particular the JRS dynamic rollover test results, in conjunction with NHTSA and IIHS statistical analyses, and the biomechanical injury correlation studies¹ provide that basis. A consumer rollover rating system is long overdue. The best way to rate the crashworthiness injury potential of vehicles in rollovers is by utilizing a JRS dynamic test. Rating vehicles simply by FMVSS 216 gives grossly misleading (both over and understated) injury rate results.² CfIR's proposed system includes a factored and weighted analysis by fatality rate and vehicle performance frequency in all major accident modes.

JRS Ratings: JRS dynamic tests were performed on 10 vehicles. Three of the vehicles tested earned “good” ratings, two were “acceptable”, two were “marginal” and three were rated “poor”.


JRS Testing - Click on vehicle below for description and test.

Historical Testing Results

Volvo XC90

Honda CRV

Honda Ridgeline

Jeep Grand Cherokee

Chevrolet Tahoe


JRS Rollover Vehicle Compare

SUV'S Volvo XC90 (2005) Honda CRV (2007) Honda Ridgeline (2006) Jeep Grand Cherokee (2007) Chevrolet Tahoe (2007)
Roll 1 2 1 2 1 2 1 2 1 2
Roof FMVSS 216 SWR 4.6 4.6 2.6 2.6 2.4 2.4 2.2 2.2 2.1 2.1
Road Speed (mph) 15 15 15 15 15 15 15 15 15 15
Pitch Angle at Impact 5° 10° 5° 10° 5° 10° 5° 10° 5° 10°
                     

A-Pillar

                   
Peak Dynamic Crush (in) 1.7 3.1 3.4 6.5 7.8 14.4 8.4 11.8 7.9 14.0
Cumulative Residual Crush (in) 0.5 1.9 1.8 3.6 5.0 10.9 6.5 9.1 5.8 10.9
Peak Crush Speed (mph) 1.9 2.6 4.0 5.3 8.2 15.0 7.3 8.6 6.1 11.6
                     

B-Pillar

                   
Peak Dynamic Crush (in) 1.2 2.1 2.0 3.4 6.0 11.1 7.3 10.1 5.2 9.8
Cumulative Residual Crush (in) 0.2 0.7 0.8 1.4 3.4 7.4 5.6 7.8 3.5 6.9
Peak Crush Speed (mph) 1.7 2.2 2.6 3.4 5.6 6.9 7.9 6.5 4.2 7.0
                     

Neck

                   
Compression Neck Load, Fz (N) 2889 3628 5583 3687 10006 4685 9757 6781 6101 3318
Peak Upper Neck, Flexion Moment (N-m) 128 259 255 328 492 324 470 396 304 247
Upper Neck, Nij* 0.52 1.05 1.02 1.30 1.64 1.19 1.75 2.07 1.09 0.81
Lower Neck, Nij* 0.62 0.87 1.20 1.10 2.10 1.06 2.00 1.59 1.02 0.87
                     



PASSENGER CARS VW Jetta (2007) Toyota Camry (2007) Hyndai Sonata (2006) Chrysler 300 (2006) Pontiac G6 (2006)
Roll 1 2 1 2 1 2 1 2 1 2
Roof FMVSS 216 SWR 5.1 5.1 4.3 4.3 3.2 3.2 2.5 2.5 2.3 2.3
Road Speed (mph) 15 15 15 15 15 15 15 15 15 15
Pitch Angle at Impact 5° 10° 5° 10° 5° 10° 5° 10° 5° 10°
                     

A-Pillar

                   
Peak Dynamic Crush (in) 2.7 6.3 3.4 7.2 4.7 6.9 8.4 10.4 7.1

10.0

Cumulative Residual Crush (in) 1.0 3.4 1.6 4.3 2.6 -- 5.6 7.4 4.9 7.0
Peak Crush Speed (mph) 5.7 7.1 5.0 8.2 5.0 -- 7.5 10.6 7.5 13.1
                     

B-Pillar

                   
Peak Dynamic Crush (in) 1.5 2.4 1.8 4.2 -- 2.6 4.4 5.3 3.6 5.9
Cumulative Residual Crush (in) 0.6 1.3 0.7 2.1 -- 0.8 2.7 3.4 2.5 3.4
Peak Crush Speed (mph) 3.8 3.5 3.2 5.0 -- 4.1 5.4 7.6 6.3 8.9
                     

Neck

                   
Compression Neck Load, Fz (N) 5158 5394 4211 2669 4835 3457 5598 1979 2399 1916
Peak Upper Neck, Flexion Moment (N-m) 279 318 -- -- -- -- 414 155 198 155
Upper Neck, Nij* 0.96 1.08 0.78 0.76 1.63 1.15 1.80 0.40 0.66 0.54
Lower Neck, Nij* 1.17 1.28 -- -- -- -- 1.44 0.57 0.68 0.54