Vehicle rollover

File:Rollover(it).JPG

A rollover in southern Italy

File:Car accident-rollover.jpg

A rollover in Sydney, Australia

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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Dynamics

File:Indonesian fire fighters during a traffic accident.jpg

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

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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }} Kaller, Sicking et al, Performance of Steel-Post, W-Beam Guardrail Systems, 2007,</ref>

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.<ref>Template:Cite book</ref> 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Risk areas are coastal roads, plains and exposed bridges.<ref>Template:Cite journal</ref> Vehicles exiting a wind shadow can be subjected to instant gusts that can affect high-sided vehicles.

Vehicles

File:Vehicle rollover.jpg

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. 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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 do not 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%<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>), 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.<ref>"Iraq rollover kills Oregon soldier" Oregonian May 25, 2005 by MIKE FRANCIS</ref>

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.<ref>March 12, 2011 By Geraldine Baum, Los Angeles Times</ref>

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. Template:Sort under

Year <ref group="N">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.</ref>	Manufacturer	Model	Roll-over risk<ref group="N">Measured in a tilt test. *** > 20% > **** > 10% > *****</ref>	Grip g<ref group="N">Maximum sideways acceleration (turning force) before vehicle skids.</ref>	CoG height<ref group="N">Height of center of gravity, or Center of mass height.</ref>	Produced<ref group="N">Number of cars produced of this model.</ref>	Type	Seats	Comment
2011	Chevrolet	Tahoe	24.6%<ref>"2011 Chevrolet Tahoe" National Highway Traffic Safety Administration (click Rollover)</ref>	citation	CitationClass=web }}</ref> || || || SUV || 8 ||
2011	Ford	F-150	19.8%<ref>"2011 Ford F-150" National Highway Traffic Safety Administration (click Rollover)</ref>	citation	CitationClass=web }}</ref> || || || Truck || 4 ||
2013	Toyota	Hilux	19.1%<ref>"2013 Toyota Tacoma PU/EC 4WD " National Highway Traffic Safety Administration (click Rollover)</ref>			5 million until 2009<ref>2010 Toyota Land Cruiser - Top Speed, Top Speed</ref><ref>2010 Toyota Land Cruiser - Top Speed, EGM CarTech</ref>	Truck	4	Also named Tacoma
2011	Audi	Q7	18.5%<ref>"2011 Audi Q7 SUV AWD " National Highway Traffic Safety Administration (click Rollover)</ref>	citation	CitationClass=web }}</ref> || || || SUV || 4 ||
2013	Mercedes-Benz	M-Class	citation	CitationClass=web }}</ref> || || || || SUV || 5 ||
2013	Volvo	XC90	17.9%<ref>"2013 Volvo XC90 SUV AWD" National Highway Traffic Safety Administration (click Rollover)</ref>	citation	CitationClass=web }}</ref> || || || SUV || 5 or 7 ||
2013	BMW	X5	citation	CitationClass=web }}</ref> || || || 1 million until 2010<ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref> || SUV || 5 ||
2013	Lexus	RX	16.4%<ref>"2013 Lexus RX350 SUV AWD" National Highway Traffic Safety Administration (click Rollover)</ref>				SUV	5
2012	Chrysler	Town & Country	16.4%<ref>"2016 Chrysler Town And Country VAN FWD" National Highway Traffic Safety Administration (click Rollover)</ref>				Minivan	?
2013	Toyota	Sienna	14%<ref>"2016 Toyota Sienna VAN FWD" National Highway Traffic Safety Administration (click Rollover)</ref>				Minivan	7 or 8
2011	Toyota	Prius	12.1%<ref>"2011 Toyota Prius 4 DR FWD " National Highway Traffic Safety Administration (click Rollover)</ref>	citation	CitationClass=web }}</ref> || || 3-4 million until 2014<ref name=PiPsales092014>{{#invoke:citation/CS1|citation	CitationClass=web }} Cumulative sales include the conventional Prius, Prius c/Aqua, Prius Plug-in Hybrid and Prius α/+/V through September 2014.</ref> || || 4 || Hybrid
2011	Chevrolet	Impala	11.3%<ref>"2011 Chevy Impala " National Highway Traffic Safety Administration (click Rollover)</ref>				Sedan	4
2014	Mercedes-Benz	E-Class	9.9%<ref>"2016 Mercedes-Benz E-Class 4 DR RWD" National Highway Traffic Safety Administration (click Rollover)</ref>	citation	CitationClass=web }}</ref> || || || Sedan || 4 ||
2011	Chevrolet	Volt	9.4%<ref>"2011 Chevrolet Volt 4 DR FWD" National Highway Traffic Safety Administration (click Rollover)</ref>			citation	CitationClass=web }}</ref> || || 4 || Hybrid
2011	BMW	535	9.3%<ref>"2011 BMW 535 " National Highway Traffic Safety Administration (click Rollover)</ref>			citation	CitationClass=web }}</ref> || Sedan || 4 ||
2013	Chevrolet	Camaro	8.7%<ref>"2013 Chevrolet Camaro 2 DR RWD " National Highway Traffic Safety Administration (click Rollover)</ref>	citation	CitationClass=web }}</ref> || || || Coupe || 4 ||
2013	Tesla Motors	Model S	5.7%<ref name="2013 Tesla Model S 5 HB RWD">"2013 Tesla Model S 5 HB RWD" National Highway Traffic Safety Administration (click Rollover)</ref>	citation	CitationClass=web }}</ref> || Template:Cvt || 100,000 until 2016<ref name=Top2015Global>Template:Cite news</ref> || Sedan || 5 or 7 || Electric

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.Template:Citation needed

Roll bars and cages

{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} 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.<ref>Template:Cite journal</ref> 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.Template:Citation needed

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.Template:Citation needed

Warning signs

Some countries have a unique traffic warning sign for 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

• Ontario Wa-75R.svg

  Canada

• New Zealand Permanent Warning - Truck Advisory Speed (right).svg

  New Zealand

• UK traffic sign 513.1.svg

  United Kingdom (warning of an adverse camber)

• MUTCD W1-13R.svg

  United States

• MUTCD-MD W1-13(1)-R.svg

  United States (with speed limit number)

• Vietnam road sign W201d.svg

  Vietnam

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".<ref>The Traffic Signs Regulations and General Directions 2016</ref>

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.{{#if:|{{#if:|}}

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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.{{#if:|{{#if:|}}

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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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

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.<ref name="ec.europa.eu">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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<ref>which use non metric speed limit</ref> 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.<ref name="ec.europa.eu"/>

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.{{#if:|{{#if:|}}

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• 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.{{#if:|{{#if:|}}

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European HGVs

Within European union, it is considered that HGV rollovers do not usually result in serious injury.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Some European trucks have no ESC.<ref name="R1">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.</ref>

In Sweden one to two rollover accidents occur every day.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

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 o'clock on motorway A9 a double-decker bus going from Barcelone, Spain, to Amsterdam, Netherlands. 22 killed, 32 hurt.<ref name="h3">{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

• in the 17 May 2003 morning, a double-decker bus going from Germany to Costa-Brava, Spain. 28 killed<ref name="h3" />
• 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 motorwayTemplate:Citation needed 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.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref> 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 {{#expr: 8981/30901*100 round 1}}%, {{#expr: 10442/ 32271 *100 round 1}}% and {{#expr: 10553 /31693*100 round 1}}% of fatalities in 1994, 2003 and 2004.<ref name="DOTHS810741">DOT HS 810 741

4. Title and Subtitle

5. Report Date

An Analysis of Motor Vehicle Rollover Crashes and March 2007

Injury Outcomes</ref>

Single-vehicle rollover fatalities represents respectively 82%, 82% and 81% of all rollover fatalities in 1994, 2003 and 2004.<ref name="DOTHS810741" />

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.Template:Citation needed

Rollover contest

The driver deliberately drives one side of their vehicle onto a ramp which causes their vehicle to roll over.<ref name="Evergreen">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The winner is the driver who guides their vehicle to the most rolls.<ref name="Evergreen" />

See also

• Dynamic rollover
• Road collision types
• Roll over protection structures (ROPs)
• Body roll
• Weight transfer

External links

• The Center for Auto Safety videos (Rollover videos at the bottom).