An impact attenuator, also known as a crash cushion, crash attenuator, or cowboy cushion, is a device intended to reduce the damage to structures, vehicles, and motorists resulting from a motor vehicle collision. Impact attenuators are designed to absorb the colliding vehicle's kinetic energy. [1] [2] They may also be designed to redirect the vehicle away from the hazard or away from roadway machinery and workers. [3] Impact attenuators are usually placed in front of fixed structures near highways, such as gore points, crash barrier introductions, or overpass supports. Temporary versions may be used for road construction projects.
Impact attenuators are designed to absorb the colliding vehicle's kinetic energy to bring it to a stop safely. If no impact attenuator is present, a vehicle which strikes a rigid roadside object will suddenly stop. A person inside will promptly collide with the interior of the vehicle, and that person's internal organs will collide with their chest wall, causing severe internal injuries and possibly death. By safely dissipating the vehicle's kinetic energy, impact attenuators help prevent such injuries. [2]
Impact attenuators can be categorized by the method used to dissipate kinetic energy:
Gating impact attenuators allow vehicles impacting from the side to pass through them (akin to a gate).
Gating attenuators are more economical, but require a greater clear space surrounding them to be effective; without enough space, errant cars may pass through into another hazard, such as into lanes of opposing traffic. [4] [5]
Water-filled attenuators consist of containers filled with water to absorb impact energy. They are typically not anchored to the ground, and therefore benefit from easy deployment and relocation using barrier transfer machines and cranes. They are non-redirective, meaning they do not deflect vehicles that impact the side back into the roadway. The energy of the impacting vehicle accelerates the water in the barrels vertically and laterally consuming that energy in work done on the water. Additionally, this work is done over time which reduces the deceleration (negative acceleration) applied to the vehicle occupants. A smaller amount of energy is consumed in the work of crumpling the plastic containers. In cold climates, water-filled attenuators are either avoided, or have additives such as magnesium chloride salt added to them to prevent freezing.
A Fitch barrier consists of sand-filled plastic barrels, usually yellow-colored with a black lid. The "Fitch Highway Barrier System" was invented by race car driver John Fitch after the 1955 24 Hours of Le Mans race when his co-driver, Pierre Levegh rear-ended Austin-Healey driver Lance Macklin at high speed, launching his car through the air and into the spectator's area. The car burst into flames and took the lives of Pierre and 84 spectators in one of the worst accidents in racing history. He stated he was inspired by sand-filled fuel cans which he used to protect his tent from strafing during World War II. [6] Early prototypes were self funded and tested due to low initial support. As a proof of concept Fitch used liquor barrels filled with sand to create the necessary impact attenuation, then personally crashed reinforced vehicles into them while recording with a high speed camera to capture the rate of deceleration.
Fitch barriers are often found in a triangular arrangement at the end of a guard rail between a highway and an exit lane (the area known as the gore), along the most probable line of impact. The barriers in front contain the least sand, with each successive barrel containing more, so that when a vehicle collides with the barrels they shatter, the kinetic energy is dissipated by scattering the sand, and the vehicle decelerates smoothly instead of violently striking a solid obstruction, reducing the risk of injury to the occupants.
Fitch barriers are widely popular due to their effectiveness, low cost, and ease of setup and repair or replacement. Since first being used in the late 1960s, it is estimated that they have saved as many as 17,000 lives and approximately $400 million per year in property damage and medical expenses. [7] [8]
Non-gating impact attenuators arrest the motion of vehicles that impact head-on, whilst deflecting vehicles that impact the side of the barrier. They are anchored and more expensive, but can be used in tighter spaces. [4]
Crash cushions are constructed of multiple segments, which crumple into each other when collided with to absorb the impact. Their main benefit is in their reusability; some attenuators can automatically return to their original position after a crash, [9] while others require minimal repairs. [10]
Truck mounted attenuators (TMA), similar in some ways to railcar buffers, can be deployed on vehicles that are prone to being struck from behind, such as snow plows and road construction or maintenance vehicles. Work zone regulations often specify a minimum buffer distance between the attenuator truck and the work area, and a minimum mass for the truck, to minimize the chances that the truck will be pushed forward by a crash into the workers or machinery. This is especially important in mobile work zones where the truck's parking brake may not be engaged. The truck may also be in movement (albeit slower than the vehicles that could crash into it).
In some countries, such as Sweden, road safety authorities operate dedicated TMA vehicles [11] registered as emergency vehicles, able to be dispatched to blockages or emergencies.
TMA vehicles are better suited for protecting emergency or construction workers on roadways than non-specialized vehicles, such as firetrucks. TMA vehicles have several benefits over firetrucks, such as lower purchase and repair cost, improved firefighting capacity (because firetrucks are available for use and won't be damaged), and enhanced safety for the occupants of the impacting vehicles. This is because TMA vehicles are designed to absorb the energy of the impact, while firetrucks are too rigid and can cause severe injuries or death. [12]
In the United States, impact attenuators are tested and classified according to AASHTO Manual for Assessing Safety Hardware (MASH), [13] first issued in 2016 to supersede National Cooperative Highway Research Program (NCHRP) Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features (1993). [14] Classification is based on the maximum speed of a vehicle during a collision for which the attenuator is designed. The Federal Highway Administration reviews equipment to providing hardware eligibility letters for federal aid reimbursement. [15]
An airbag is a vehicle occupant-restraint system using a bag designed to inflate exceptionally quickly and then deflate during a collision. It consists of an airbag cushion, a flexible fabric bag, an inflation module, and an impact sensor. The purpose of the airbag is to provide a vehicle occupant with soft cushioning and restraint during a collision. It can reduce injuries between the flailing occupant and the vehicle's interior.
Crumple zones, crush zones, or crash zones are a structural safety feature used in vehicles, mainly in automobiles, to increase the time over which a change in velocity occurs from the impact during a collision by a controlled deformation; in recent years, it is also incorporated into trains and railcars.
A crash test is a form of destructive testing usually performed in order to ensure safe design standards in crashworthiness and crash compatibility for various modes of transportation or related systems and components.
A rear-end collision, often called rear-ending or, in the UK, a shunt, occurs when a forward-moving vehicle crashes into the back of another vehicle in front of it. Similarly, rear-end rail collisions occur when a train runs into the end of a preceding train on the same track. Common factors contributing to rear-end collisions include driver inattention or distraction, tailgating, panic stops, brake checking and reduced traction due to wet weather or worn pavement.
Road traffic safety refers to the methods and measures used to prevent road users from being killed or seriously injured. Typical road users include pedestrians, cyclists, motorists, vehicle passengers, and passengers of on-road public transport.
Crash incompatibility, crash compatibility, vehicle incompatibility, and vehicle compatibility are terms in the automobile crash testing industry. They refer to the tendency of some vehicles to inflict more damage on another vehicle in two-car crashes. Vehicle incompatibility is said to lead to more dangerous, fatal crashes, while compatibility can prevent injury in otherwise comparable crashes.
A bumper is a structure attached to or integrated with the front and rear ends of a motor vehicle, to absorb impact in a minor collision, ideally minimizing repair costs. Stiff metal bumpers appeared on automobiles as early as 1904 that had a mainly ornamental function. Numerous developments, improvements in materials and technologies, as well as greater focus on functionality for protecting vehicle components and improving safety have changed bumpers over the years. Bumpers ideally minimize height mismatches between vehicles and protect pedestrians from injury. Regulatory measures have been enacted to reduce vehicle repair costs and, more recently, impact on pedestrians.
The European New Car Assessment Programme is a European voluntary car safety performance assessment programme based in Leuven, Belgium. Formed in 1996, the first results were released in February 1997. It was originally started by the Transport Research Laboratory for the UK Department for Transport but later backed by several European governments, as well as by the European Union (EU). Their slogan is "For Safer Cars".
A Jersey barrier, Jersey wall, or Jersey bump is a modular concrete or plastic barrier employed to separate lanes of traffic. It is designed to minimize vehicle damage in cases of incidental contact while still preventing vehicle crossovers resulting in a likely head-on collision. Jersey barriers are also used to reroute traffic and protect pedestrians and workers during highway construction. They are named after the U.S. state of New Jersey which first started using the barriers as separators between lanes of a highway in the 1950s.
A buffer stop, bumper, bumping post, bumper block or stopblock (US), is a device to prevent railway vehicles from going past the end of a physical section of track.
The Steel And Foam Energy Reduction Barrier, sometimes generically referred to as a soft wall, is a technology found on oval automobile race tracks and high speed sections of road and street tracks, intended to absorb and reduce kinetic energy during the impact of a high speed crash, and thus, lessen injuries sustained to drivers and spectators. It was designed by a team of engineers at the Midwest Roadside Safety Facility at the University of Nebraska-Lincoln. It was developed from 1998–2002, and first installed at the Indianapolis Motor Speedway in May 2002.
A side collision is a vehicle crash where the side of one or more vehicles is impacted. These crashes typically occur at intersections, in parking lots, and when two vehicles pass on a multi-lane roadway.
In mechanics, an impact is when two bodies collide. During this collision, both bodies decelerate. The deceleration causes a high force or shock, applied over a short time period. A high force, over a short duration, usually causes more damage to both bodies than a lower force applied over a proportionally longer duration.
The Mercedes-Benz "Ponton" series are a range of sedans / saloon car models from Daimler-Benz, introduced starting in 1953, and subsequently nicknamed 'Ponton', referring to its ponton styling, a prominent styling trend that unified the previously articulated hood, body, fenders and runnings boards into a singular, often slab-sided envelope. At the time, Mercedes itself did not refer to any of its cars using the nickname.
Béla Barényi was an ethnic Hungarian engineer from Austria-Hungary, who was a prolific inventor, sometimes even compared to Thomas Edison. Barényi made numerous crash protection inventions, and is therefore regarded as the father of passive safety in automotive design.
A runaway truck ramp, runaway truck lane, escape lane, safety ramp, emergency escape ramp, or truck arrester bed is a traffic device that enables vehicles which are having braking problems to stop safely. It is typically a long, sand- or gravel-filled lane connected to a steep downhill grade section of a main road, and is designed to accommodate large trucks or buses. It allows a moving vehicle's kinetic energy to be dissipated gradually in a controlled and relatively harmless way, helping the operator stop it safely.
Traffic barriers keep vehicles within their roadway and prevent them from colliding with dangerous obstacles such as boulders, sign supports, trees, bridge abutments, buildings, walls, and large storm drains, or from traversing steep (non-recoverable) slopes or entering deep water. They are also installed within medians of divided highways to prevent errant vehicles from entering the opposing carriageway of traffic and help to reduce head-on collisions. Some of these barriers, designed to be struck from either side, are called median barriers. Traffic barriers can also be used to protect vulnerable areas like school yards, pedestrian zones, and fuel tanks from errant vehicles.
Energy absorber may refer to:
A cable barrier, sometimes referred to as guard cable or wire rope safety barrier (WRSB), is a type of roadside or median safety traffic barrier/guard rail. It consists of steel wire ropes mounted on weak posts. As is the case with any roadside barrier, its primary purpose is to prevent a vehicle from leaving the traveled way and striking a fixed object or terrain feature that is less forgiving than itself. Also similar to most roadside barriers, cable barriers function by capturing and/or redirecting the errant vehicle.
Road traffic collisions generally fall into one of five common types: