Crash cushions

Vehicle restraint systems such as safety fence and crash cushions are designed to minimise the severity of an accident when an errant vehicle leaves the carriageway rather than preventing an accident happening. 

Birmingham crash cushion installations show a 200% rate of return, with a significant reduction in accident severity. 

To allow for the development of a nniform guideline for selecting the most appropriate VRS performance requirements for the given conditions, a number of the Conference of Enropean Directors of Road (CEDR) members have collaborated to fund the research project Selection of Appropriate Vehicle Restraint Systems (SAVeRS) within the 2012 Transnational Road Research Programme call Safety . The aim of the SAVeRS project is to produce a practical and readily understandable VRS guidance document and a user-friendly Web-based tool that will allow the selection of the most appropriate solution in different road and traffic configurations for all types of VRS safety barriers, crash cushions, terminals and transitions and motorcycle protection devices. 

Once a complete set of robust parameters had been determined, the data matrix was divided into tabs, identifying those parameters related to the decisions for each VRS type, i.e. roadside safety barriers, median safety barriers, bridge parapets, crash cushions, transitions, terminals and motorcyclist protection systems (MPS). Due to the low level of published guidance for terminals, transitions and MPS, these were removed from the data matrix. For each parameter, it was then determined whether it applied to the decision to install a VRS or to the selection of the performance for the VRS. 

For the most performance requirement in the most common VRS application (roadside barriers), it is factors such as the presence of stractures and railway lines, the presence and proximity of bodies of water and non-deformable roadside obstacles, the average annual daily traffic and actual speeds and the presence of adverse road geometry which are most prominent. While factors such as aesthetics and cost are mentioned in some national guidelines and standards, their frequency is low. While the majority of the countries have guidelines and/or standards related to roadside and median barriers, there is generally limited guidance for other VRS systems such as crash cushions, transitions and MRS. 

ELV 95] Elvik R., The safety value of guardrails and crash cushions a meta-analysis of evidence from evaluation studies . Journal of Accident Analysis and Prevention, vol. 27, pp. 523-549,1995. 

Fixed Objects For IR projects Address obvious objects that are within the prevailing clear area and within the ROW based on engineering judgment from a field visit (e.g., tree removal on the outside of a curve or installation of traversable driveway culvert end sections). For 2R/3R projects Reestablish the clear zone and remove, relocate, modify to make crash worthy, shield by guide rail/crash cushion, or delineate any fixed objects. For guidance on identifying fixed objects, refer to HDM 10.3.1.2 B. ... 

Any vehicle stationary in a trafficked lane presents a hazard regardless of advanced signing whether it is a block vehicle fitted with a crash cushion or a police car with blue lights flashing. In areas where there is intermittent, substandard or no hard shoulder, the option for using mobile signing safely is academic. 

Vehicle restraint systems such as safety fence and crash cushions are designed to minimise... 

Polyurethane foams are lighter than foam rubber and have displaced many of its applications, such as in bedding, cushions, car seats, armrests, and crash pads. Laminates are used widely in clothing as padding. 

Cushioning All individual flexible cushioning materials used in seat cushions, mattresses, mattress pads, armrests, crash pads, and grab rail padding3-e ASTM D 3675 Is <25 ASTM E 662 Ds (1.5) < 100 ZX (4.0) < 175... 

In the early 1980 s a neoprene-type foam (VONAR) made by Du Pont was developed specifically for use as a comfort cushioning material for critical applications where low flammabUity was required, such as in transport aircraft seat cushions. This material is designed for use over flame-retardant polymethane foam and is believed to provide 50 seconds more of evacuation time in the event of a post-crash fire. VONAR has a density of 10.66 Ib/ft , compared to 7-8 Ib/ft for standard neoprene foam, and 1.2-2 Ib/ft for polyurethane foam (5). 

A polymer type has its own set of physical and chemical properties that can set it apart from other polymers. For example, some are intrinsically rigid in nature, whereas others are more flexible. Some may exhibit good energy absorption charactcri.stics. whereas others have a resistance to moisture penetration. These properties make them ideal for. say, insulation, cushioning, crash pads, or floatation applications respectively. 

The major interest in flexible polyurethane foams is for cushions and other upholstery materials. Principal market outlets include furniture cushioning, carpet underlay, bedding, automotive seating, crash pads for automobiles, and packaging. The density range of flexible foams is usually 1-6 Ib/ft. (0.016-0.096 g/cm ). The foam is made in continuous loaves several feet in width and height and then sliced into slabs of desired thickness. 

The largest-volume use of flexible foam is furniture and bedding, which account for nearly 47% of the flexible polyurethane foam market. Almost all furniture cushioning is polyurethane. Automobile seating is either made from flexible slabstock or poured directly into frames, so-called deep seating, using HR chemical formulations. Semiflexible polyurethane foams find use in crash pads, arm and head rests, and door panels. 

Note Weather is often cited as a main cause of CMV accidents by drivers. However, as the above trend in fatality crashes indicates, weather is rarely the cause. Also, in most cases when weather does become a factor, driver error (following too close for conditions, operating too fast for conditions, or not maintaining an adequate cushion of safety in adverse weather conditions) is the real cause. 

Rollover If there is enough lateral impact and movement, a vehicle may roll over. If tires shde and there is a change in resistance or they contact another object, a rollover can result. The vehicle structure may crash during the rollover, causing reduction of the occupant space. Because occupants may be thrown around, use of restraints will lessen the chance for injury. Some vehicles incorporate side impact stracmral elements to minimize reduction of occupant space. An increasing number of models include side impact air bags to cushion impacts on occupants and help restrain them from rollover injury. 

Shock absorbing liquid (SALi) Technology -based cushions consist of small, compressible elastic capsules blended with an incompressible matrix fluid for protection from violent impacts, crash, vibrations and shock waves. It is suggested that the cushions offer four damage mitigation mechanisms in the impact energy absorption process ... 

The road is wet, the traffic heavy, and as you fumble with your cell phone the traffic light ahead of you turns red. You slam the brakes an instant too late and crash into the car in front of you. The next moment you have a nylon bag in your face and are covered with talcum powder—the experience of a modern-day collision. Since their introduction in the 1980s, air bags have saved thousands of lives by providing—at just the right instant—a cushion of air between the driver and the rest of the car. 

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