A rollover in Sydney, Australia on Christmas Day, 2001.

A rollover or overturn is a type of vehicle crash in which a vehicle tips over onto its side or roof. Rollovers have a higher fatality rate than other types of vehicle collisions.[1]

Dynamics

A rolled over Box truck being handled by fire fighters in Jakarta, Indonesia
A rollover in southern Italy

Vehicle rollovers are divided into two categories: tripped and untripped. Tripped rollovers are caused by forces from an external object, such as a curb or a collision with another vehicle. Untripped rollovers are the result of steering input, speed, and friction with the ground.[2] Trailers that are not roll-coupled (i.e. those that use a trailer coupling rather than a fifth wheel) are more prone to rolling as they do not have the tractor unit or prime mover for additional stability.

Untripped rollovers

Untripped rollovers occur when cornering forces destabilize the vehicle. As a vehicle rounds a corner, three forces act on it: tire forces (the centripetal force), inertial effects (the centrifugal force), and gravity. The cornering forces from the tire push the vehicle towards the center of the curve. This force acts at ground level, below the center of mass. The force of inertia acts horizontally through the vehicle's center of mass away from the center of the turn. These two forces make the vehicle roll towards the outside of the curve. The force of the vehicle's weight acts downward through the center of mass in the opposite direction. When the tire and inertial forces are enough to overcome the force of gravity, the vehicle starts to turn over.

Tripped rollovers

The most common type of tripped rollover in light passenger vehicles occurs when a vehicle is sliding sideways, and the tires strike a curb, dig into soft ground, or a similar event occurs that results in a sudden increase in lateral force. The physics are similar to cornering rollovers. In a 2003 report, this was the most common mechanism, accounting for 71% of single-vehicle rollovers.[3]

Another type of tripped rollover occurs due to a collision with another vehicle or object. These occur when the collision causes the vehicle to become unstable, such as when a narrow object causes one side of the vehicle to accelerate upwards, but not the other. Turned down guard rail end sections have been shown to do this. A side impact can accelerate a vehicle sideways. The tires resist the change, and the coupled forces rotate the vehicle. In 1983, crash tests showed that light trucks were prone to rolling over after colliding with certain early designs of guide rail.[4]

A rollover can also occur as a vehicle crosses a ditch or slope. Slopes steeper than 33% (one vertical unit rise or fall per three horizontal units) are called "critical slopes" because they can cause most vehicles to overturn.[5] A vehicle may roll over when hitting a large obstacle with one of its wheels or when maneuvering over uneven terrain. A trailer jackknife can push the towing vehicle into a rollover scenario if the vehicle is subject to a tripped scenario (soft ground or a curb).

Strong winds may cause high-sided vehicles such as trucks, buses and vans to be blown over.[6] Risk areas are coastal roads, plains and exposed bridges.[7] Vehicles exiting a wind shadow can be subjected to instant gusts that can affect high-sided vehicles.

Vehicles

A vehicle rollover minutes after a crash

All vehicles are susceptible to rollovers to various extents. Generally, rollover tendency increases with the height of the center of mass, narrowness of the axle track, steering sensitivity, and increased speed.

The rollover threshold for passenger cars is over 1 g of lateral acceleration. The Tesla Model S has an unusually low rollover risk of 5.7% due to its low center of mass.[8][9] Light trucks will roll over at lateral accelerations of 0.8 to 1.2 g. Large commercial trucks will roll at lateral accelerations as low as 0.2 g [10] Trucks are more likely to roll over than passenger cars because they usually have taller bodies and higher ground clearance. This raises the center of mass.

SUVs are prone to rollover, especially those outfitted with long travel off-road suspensions. The increased suspension height for increased clearance off-road raises the center of mass.

Full-size vans don't usually have off-road suspensions, but their increased body height makes them more prone to tip. Fifteen passenger vans such as the Ford E-Series (at 27.9%[11]), are particularly notorious for rolling over because their height is increased by the heavy-duty suspensions necessary to carry large numbers of people. The rollover tendency is increased when the vehicles are heavily loaded. It is recommended to not load anything on the roof of such vans, and to use drivers experienced or trained in safe operation of the vehicle. In such cases, familiarity with the vehicle's behavior loaded and unloaded, avoiding sudden swerving maneuvers, and reducing speed through tight turns can greatly decrease the rollover risk associated with these vehicles.

Manufacturers of SUVs often post warnings on the driver's sun-visor. Among the vehicles which have received publicity for tendencies to roll over are the Ford Bronco II, Suzuki Samurai, Jeep CJ, Mitsubishi Pajero/Montero, and Isuzu Trooper.

Military vehicles have a much wider wheel track than civilian SUVs, making them more difficult to roll over. However, IEDs in Iraq and Afghanistan cause roll overs not seen by civilian vehicles. The top turret gunner is particularly vulnerable.[12]

A tall passenger coach made US headlines when 15 passengers were killed in New York in 2011. The bus swerved, flipped on its side and hit a pole which split off the top of the vehicle.[13]

General list of roll-over risk

Vehicles sold in the United States, sorted by risk as evaluated by the U.S. National Highway Traffic Safety Administration. Click <> to sort by other parameters.

Year
[N 1]		ManufacturerModelRoll-over
risk[N 2]		Grip
g[N 3]		CoG
height[N 4]		Produced[N 5]TypeSeatsComment
2011ChevroletTahoe24.6%[14]0.79[15]SUV8
2011FordF-15019.8%[16]0.71[17]Truck4
2013ToyotaHilux19.1%[18]5 million until 2009[19][20]Truck4Also named Tacoma
2011AudiQ718.5%[21]0.85[22]SUV4
2013Mercedes-BenzM-Class17.9%[23]SUV5
2013VolvoXC9017.9%[24]0.77[25]SUV5 or 7
2013BMWX517.4%[26]1 million until 2010[27]SUV5
2013LexusRX16.4%[28]SUV5
2012ChryslerTown & Country16.4%[29]Minivan ?
2013ToyotaSienna14%[30]Minivan7 or 8
2011ToyotaPrius12.1%[31]0.79[32]3-4 million until 2014[33]4Hybrid
2011ChevroletImpala11.3%[34]Sedan4
2014Mercedes-BenzE-Class9.9%[35]0.87[36]Sedan4
2011ChevroletVolt9.4%[37]93,000 until 2015[38]4Hybrid
2011BMW5359.3%[39]5 million until 2009[40]Sedan4
2013ChevroletCamaro8.7%[41]0.98[42]Coupe4
2013Tesla MotorsModel S5.7%[8]0.92[43]18 in (46 cm)100,000 until 2016[44]Sedan5 or 7Electric
  1. ↑ Model Year of car crash-tested, not year of Overall Rating. Older crash tests usually carry over to newer car models; easily checked by comparing ratings and document numbers for different years.
  2. ↑ Measured in a tilt test. *** > 20% > **** > 10% > *****
  3. ↑ Maximum sideways acceleration (turning force) before vehicle skids.
  4. ↑ Height of center of gravity, or Center of mass height.
  5. ↑ Number of cars produced of this model.

Exit

After a rollover, the vehicle may end up lying on its side or roof, often blocking the doors and complicating the escape for the passengers. Large passenger vehicles such as buses, trams, and trolley buses that have doors on one side only usually have one or more methods of using windows for escape in case of a rollover. Some have special windows with handles to pull so that windows can be used as an emergency exit. Some have tools for breaking the windows and making an improvised exit. Some have emergency exit door or hatches in their roofs or on the opposite side of the bus to the usual entry door. Some combine two or more of these escape methods.

Roll bars and cages

Rollover crashes are particularly deadly for the occupants of a vehicle when compared to frontal, side, or rear crashes, because in normal passenger vehicles, the roof is likely to collapse in towards the occupants and cause severe head injuries.[45] The use of roll cages in vehicles would make them much safer, but in most passenger vehicles their use would cut cargo and passenger space so much that their use is not practical. The Jeep Wrangler, a vehicle which is short, narrow, and designed to be used on uneven terrain, is unusual in that it comes with a roll bar as standard equipment.

The decline in popularity of convertibles in the US was partly caused by concern about lack of protection in rollover accidents, because most convertibles have no protection beyond the windshield frame. Some convertibles provide rollover protection using two protruding curved bars behind the headrests. Some Mercedes-Benz convertibles have a retractable roll bar which deploys in case of an accident. Race cars almost always have roll cages, since racing is very likely to result in a rollover. In addition, the roll cage's chassis-stiffening effect is usually seen as a benefit to the car.

Warning signs

Some countries have a unique sign warning of curves and other areas with an increased danger of rollover for trucks and other vehicles with high centers of gravity. These signs may include an advisory safe speed to avoid rolling over. This speed is typically set by measuring a maximum g-force permitted around the corner to remain well under the maximum static roll threshold.[46]

In the UK, the "adverse camber" plate comes with a warning sign such as "roundabout ahead", "bend ahead", "junction on (...) a bend ahead", or "series of bends ahead".[47]

Europe

In most European countries the official accident statistics contain no information on rolling cars, only Great Britain can deliver official statistical data. Regarding other sources, only a few accident databases on rollover accidents exist.

— European union Rollover Final Public Report - Annexes (May 2006)[48]

Although only less than 10% of all vehicle accidents with severe injuries involve rollovers, approximately 25% of all seriously injured occupants were involved in accidents where their car rolled. These numbers are currently increasing, as rollover frequency of several new vehicle types like mini vans, SUV or MPV is a lot higher than for most conventional cars.

— European union Rollover Final Public Report - Annexes (May 2006)[48]

Inside the European union, most rollovers occur off the carriageway. When the occupant is not ejected from the vehicle and the car does not strike any rigid objects, rollovers are the least injurious of the different impact types, because deceleration is longer and slower.[49]

Nonetheless, rollover risk depends upon the centre of gravity, suspension characteristics and loads carried. The severity of injury depends on the presence of crash-protective roadsides and the speed of impact.[50] In most of western Europe over 3,5 tonnes HGV have a speed limited from 80 km/h or 90 km/h, except in Great-Britain and Northern Ireland[51] and Italy, Romania and Bulgaria which have HGV speed limit up to 110 km/h. In France, HGV can reach 90 km/h on the motorway network and some other roads but are limited to the 80 km/h general speed limit of the local/secondary road network.

It is considered that Electronic Stability Programmes can contribute to reduce some accidents including rollovers.[50]

Differences between European and US rollover

The vehicle fleets in Europe and in the US differ from each other. For instance, the US has significantly more SUVs, MPVs, Pick-ups and other vehicles with a high center of gravity. Further differences can be found when considering the road environment, e.g. availability and type of barriers, road side objects, congestion levels, road surfaces, proximity of buildings. Moreover, the belt wearing rate in the US, particularly in those vehicles prone to rollover, is lower than in European countries. Finally, there are differences in legislation which affect vehicle design and/or driver behavior.

— European union Rollover Final Public Report - Annexes (May 2006)[48]
  • Occupant ejection is an important factor, especially when serious injuries are considered
  • The risk of injury increases substantially when occupants are unrestrained
  • Most rollovers occur about the longitudinal axis of the vehicle
  • Most vehicle rollovers involve one complete roll or less
  • Ejection takes place most frequently through the side windows.
    — European union Rollover Final Public Report - Annexes (May 2006)[48]

European HGVs

Within European union, it is considered that HGV rollovers do not usually result in serious injury.[52]

Some European trucks have no ESC.[53]

In Sweden one to two rollover accidents occur every day.[54]

European double-decker bus

In France, several double-decker bus performed rollover making BEATT to recommend regulation improvement to make ESC mandatory, while seat belt has become mandatory in the meantime:

  • on 10 July 1995 at one oclock on motorway A9 a double-decker bus going from Barcelone, Spain, to Amsterdam, Netherlands. 22 killed, 32 hurt.[55]
  • in the 17 May 2003 morning, a double-decker bus going from Germany to Costa-Brava, Spain. 28 killed[55]
  • on 11 September 2012 at 8h07, a 4 meters height and 12 meters long, 72 seats double-decker bus going from Poland to southern France perform a rollover on the A36 motorway with ABS but without ESC at 97 km/h and then 40 km/h speed. Seat-belt were missing. 2 killed, 42 hurt. The bus is destroyed.
  • In December 2019, a double-decker bus perform a rollover on Técou, near Gaillac, Tarn, but people are protected by their seat-belt.[56]

This led to European regulation (CE) 661/2009 and to UNECE regulation 66 revision to take into account such an issue.

United States

In the US, rollover fatalities represents respectively 29.1%, 32.4% and 33.3% of fatalities in 1994, 2003 and 2004.[57]

Single-vehicle rollover fatalities represents respectively 82%, 82% and 81% of all rollover fatalities in 1994, 2003 and 2004.[57]

Rollover fatalities represents respectively 29%, 32% and 33% of fatalities in 1994, 2003 and 2004.[57]

US States & Territories where rollover includes a bigger part of fatalities includes:

  • Wyoming: 69%, 57% and 66%
  • Montana: 57%, 63% and 67%
  • New Mexico: 57%, 62% and 53%

US States & Territories where rollover includes a lower part of fatalities includes:

  • Puerto Rico: 10%, 14% and 12%
  • Mississippi: 15%, 17% and 18%
  • District of Columbia: 29%, 7% and 10%

Competition

A skilled driver may stop a rollover by stopping a turn. Stunt drivers deliberately use ramps to launch a rollover. Vehicles with a high center of gravity are easily upset or "rolled." Short of a rollover, stunt drivers may also drive the car on two wheels for some time, but this requires precise planning and expert driver control. Specialized safety equipment is often utilized.

Rollover contest

The driver deliberately drives one side of their vehicle onto a ramp which causes their vehicle to roll over.[58] The winner is the driver who guides their vehicle to the most rolls.[58]

See also

References

  1. ↑ "Rollover". NHTSA. Retrieved 2015-09-16.
  2. ↑ Gridsada Phanomchoeng and Rajesh Rajamani (December 2012). "Prediction and Prevention of Tripped Rollovers". Department of Mechanical Engineering, University of Minnesota. Archived from the original on 2020-07-05. Retrieved 2013-02-05.
  3. ↑ "Examination of Rollover Crash Mechanisms and Occupant Outcomes". National Highway Transportation Safety Administration. 2003.
  4. ↑ "Performance of Steel-Post, W-Beam Guardrail Systems (Paper No. 07-2642)" (PDF). Archived from the original (PDF) on 2010-06-05. Retrieved 2009-04-23. Kaller, Sicking et al, Performance of Steel-Post, W-Beam Guardrail Systems, 2007,
  5. ↑ Roadside Design Guide. American Association of State Highway Transportation Officials. 2002. pp. 3–13.
  6. ↑ "How do rollover accidents happen and what causes them". 24 March 2021.
  7. ↑ Pryor, S. C.; Barthelmie, R. J.; Young, D. T.; Takle, E. S.; Arritt, R. W.; Flory, D.; Gutowski, W. J.; Nunes, A.; Roads, J. (2009). "Wind speed trends over the contiguous United States". Journal of Geophysical Research. 114 (D14). Bibcode:2009JGRD..11414105P. doi:10.1029/2008JD011416. S2CID 54761873.
  8. 1 2 "2013 Tesla Model S 5 HB RWD" National Highway Traffic Safety Administration (click Rollover)
  9. ↑ Read, Richard (2013-08-20). "Tesla Model S: So Safe, It Broke NHTSA's Testing Equipment". TheCarConnection.com. Retrieved 2015-09-01. NHTSA's normal tests couldn't induce the car to flip, so the agency had to resort to "special means". Tesla credits the sedan's battery pack for that, which gives the Model S a very low center of gravity
  10. ↑ C. B. Winkler and R. D. Ervin (1999). "Rollover of Heavy Commercial Vehicles". The University of Michigan Transportation Research Institute.
  11. ↑ "2012 Ford E-150 Passenger VAN RWD". U.S. Department of Transportation. Retrieved 2015-09-16.
  12. ↑ "Iraq rollover kills Oregon soldier" Oregonian May 25, 2005 by MIKE FRANCIS
  13. ↑ March 12, 2011 By Geraldine Baum, Los Angeles Times
  14. ↑ "2011 Chevrolet Tahoe" National Highway Traffic Safety Administration (click Rollover)
  15. ↑ "2015 Chevrolet Tahoe LTZ vs. 2015 Ford Expedition Platinum: Final Scoring, Performance Data, and Complete Specs". March 17, 2015. Archived from the original on 2015-03-17.
  16. ↑ "2011 Ford F-150" National Highway Traffic Safety Administration (click Rollover)
  17. ↑ "2011 Ford F-150 3.7 V6 Test – Review – Car and Driver". September 5, 2015. Archived from the original on 2015-09-05.
  18. ↑ "2013 Toyota Tacoma PU/EC 4WD " National Highway Traffic Safety Administration (click Rollover)
  19. ↑ 2010 Toyota Land Cruiser - Top Speed, Top Speed
  20. ↑ 2010 Toyota Land Cruiser - Top Speed, EGM CarTech
  21. ↑ "2011 Audi Q7 SUV AWD " National Highway Traffic Safety Administration (click Rollover)
  22. ↑ "Introduction". May 25, 2013. Archived from the original on 2013-05-25.
  23. ↑ "2013 Mercedes-Benz ML-Class SUV 4WD". U.S. Department of Transportation. Retrieved 2015-09-23.
  24. ↑ "2013 Volvo XC90 SUV AWD" National Highway Traffic Safety Administration (click Rollover)
  25. ↑ "Volvo XC90 Review - Volvo XC90 Car Pricing, Photos and Specs - CARandDRIVER". September 6, 2015. Archived from the original on 2015-09-06.
  26. ↑ "2013 BMW X5 Xdrive35D SUV AWD". U.S. Department of Transportation. Retrieved 2015-09-23.
  27. ↑ "BMW builds 1,000,000th X5—Autoblog". Autoblog. 8 June 2010. Retrieved 4 October 2014.
  28. ↑ "2013 Lexus RX350 SUV AWD" National Highway Traffic Safety Administration (click Rollover)
  29. ↑ "2016 Chrysler Town And Country VAN FWD" National Highway Traffic Safety Administration (click Rollover)
  30. ↑ "2016 Toyota Sienna VAN FWD" National Highway Traffic Safety Administration (click Rollover)
  31. ↑ "2011 Toyota Prius 4 DR FWD " National Highway Traffic Safety Administration (click Rollover)
  32. ↑ "2012 Toyota Prius C Instrumented Test – Review – Car and Driver". September 5, 2015. Archived from the original on 2015-09-05.
  33. ↑ Toyota Global Newsroom (2014-10-14). 実績データ（ハイブリッド車グローバル販売） [Actual data (hybrid vehicles sold globally)] (in Japanese). Toyota. Archived from the original on 2014-11-05. Retrieved 2014-10-24. Cumulative sales include the conventional Prius, Prius c/Aqua, Prius Plug-in Hybrid and Prius α/+/V through September 2014.
  34. ↑ "2011 Chevy Impala " National Highway Traffic Safety Administration (click Rollover)
  35. ↑ "2016 Mercedes-Benz E-Class 4 DR RWD" National Highway Traffic Safety Administration (click Rollover)
  36. ↑ "2011 Mercedes-Benz E550 Cabriolet – Instrumented Test – Car and Driver". September 9, 2015. Archived from the original on 2015-09-09.
  37. ↑ "2011 Chevrolet Volt 4 DR FWD" National Highway Traffic Safety Administration (click Rollover)
  38. ↑ Jeff Cobb (2015-06-15). "Three More Plug-in Cars Cross 25,000 Sales Milestone". HybridCars.com. Retrieved 2015-06-27.
  39. ↑ "2011 BMW 535 " National Highway Traffic Safety Administration (click Rollover)
  40. ↑ Joseph, Noah (2008-01-30). "BMW rolls out 5 millionth 5-Series — Autoblog". Autoblog.com. Retrieved 2009-11-23.
  41. ↑ "2013 Chevrolet Camaro 2 DR RWD " National Highway Traffic Safety Administration (click Rollover)
  42. ↑ "2012 Chevrolet Camaro ZL1 Test – Review – Car and Driver". September 5, 2015. Archived from the original on 2015-09-05.
  43. ↑ Christian Seabaugh (28 October 2015). "Lightning Strikes Twice: The World's Quickest Four-Door is An Electric Sedan". Motor Trend.
  44. ↑ Cobb, Jeff (2016-01-12). "Tesla Model S Was World's Best-Selling Plug-in Car in 2015". HybridCars.com. Retrieved 2016-01-13.
  45. ↑ Rudolphi, Josie M.; Campo, Shelly; Gerr, Fred; Rohlman, Diane S. (May 2018). "Social and Individual Influences on Tractor Operating Practices of Young Adult Agricultural Workers". Journal of Adolescent Health. 62 (5): 605–611. doi:10.1016/j.jadohealth.2017.11.300. ISSN 1054-139X. PMC 8189182. PMID 29478719.
  46. ↑ "Static roll threshold calculator".
  47. ↑ The Traffic Signs Regulations and General Directions 2016
  48. 1 2 3 4 European (July 2002). "Improvement of Rollover Safety for Passenger Vehicles | TRIMIS". Trimis.ec.europa.eu. Retrieved 2022-04-18.
  49. ↑ "Cars". Mobility and transport - European Commission. October 17, 2016.
  50. 1 2 "Vehicle Safety 2018" (PDF). Archived from the original (PDF) on 2019-06-24. Retrieved 2019-06-24.
  51. ↑ which use non metric speed limit
  52. ↑ "Heavy goods vehicles". Mobility and transport - European Commission. October 17, 2016.
  53. ↑ Rapport d’enquête technique sur la collision entre un camion malaxeur et un véhicule léger survenu le 13 août 2019 sur la RD13 à Bazoches-sur-Guyonne (78), Affaire No. BEATT-2019-05, No. ISRN : EQ-BEAT--21-8--FR.
  54. ↑ "Rollover Prevention: Heavy Goods Vehicles" (PDF). Retrieved 2024-01-07.
  55. 1 2 "Chronologie : les plus graves accidents de la route en France et dans la rц╘gion depuis 1964". Sudouest.fr. 2020-07-21. Retrieved 2022-04-18.
  56. ↑ "Tarn : un autocar glisse et se renverse avec 64 personnes âgées à bord". ladepeche.fr. 2019-12-21. Retrieved 2022-04-18.
  57. 1 2 3 DOT HS 810 741 4. Title and Subtitle 5. Report Date An Analysis of Motor Vehicle Rollover Crashes and March 2007 Injury Outcomes
  58. 1 2 "Race Descriptions: Rollover Contest". Evergreen Speedway. 2006-03-26. Archived from the original on 2009-02-27. Retrieved 2008-08-07.
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