Guard rail

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For other uses, see guardrail (disambiguation).

Guard rail or guardrail, sometimes referred to as guide rail or railing, is a system designed to keep people or vehicles from (in most cases unintentionally) straying into dangerous or off-limits areas. A handrail is less restrictive than a guard rail and provides both support and the protective limitation of a boundary.

Public safety[edit]

Sign in Niagara Falls, Ontario, warning people not to climb over guard rail overlooking the Niagara River.
A handrail leading along a rocky creek crossing
A guard rail collapses at a college football game, spilling fans onto the sidelines.

Most public spaces are fitted with guard rails as a means of protection against accidental falls. Any abrupt change in elevation where the higher portion is accessible makes a fall possible. Due to this responsibility and liability, rails are placed to protect people using the premises. Guardrails are generally required by code where there is a drop of 30" or more.

Examples of this are both architectural and environmental. Environmental guard rails are placed along hiking trails where adjacent terrain is steep. Railings may also be located at scenic overlooks.

Guard rails in buildings are numerous, and are required by building codes in many circumstances. Guard rails along stairways are common, and catwalks and balconies are also lined with them. The most common residential guard rail is usually a wood railing around the deck. This typically is built on-site from pressure treated lumber, featuring a simplistic design of vertical baluster spaced every 3.5" to comply with building code. Other guard rail construction options are available. Cable railings typically use stainless steel cables strung horizontally. Glass balusters and glass panels open the view while still providing safety, as at the Grand Canyon Skywalk. With the increasing popularity of composite lumber for decking, manufacturers, like TimberTech are providing composite railing components. Wrought iron is another choice that is traditional and sturdy.

Building codes also require that no opening in a guard be of a size such that a 4" sphere may pass. There are three exceptions according to the 2003 International Building Code Section 1012.3 which allow openings to not exceed 8" or 21" depending on occupancy groups or special areas.

An architect who was famous for creative use of handrails for social stability was Alvar Aalto[citation needed]. The guard rails of an observation tower such as the Space Needle or Eiffel Tower become exaggerated to the point of becoming a fence or cage. This is also done on bridges and overpasses to prevent accidents and suicides.

Facility safety guardrail[edit]

Guardrail protecting expensive machinery

Guardrails are used in a facility setting to protect a company's greatest assets which include their people and expensive equipment.

The strongest guardrail option is utilizing a manufacturer who produces industrial strength guardrail. This guardrail is constructed out of 4" Schedule 80 6" Schedule 40. It is then sleeved in Hi-Density Thermoplastic Polyethylene which makes it maintenance free. It can be mounted using a base-plate or cored into cement to enhance the strength.

Guardrail can also be constructed of 10 gauge high-tensile steel formed into a two-rib corrugated design with two secondary ribs. This guardrail looks a lot like what you would see in an outdoor setting but is often used in facilities. The issue with this type of guardrail is that once it is impacted, it will need to be repaired and replaced.

A standard guardrail system is mounted to the floor by base plates, which are fastened with anchor bolts. Each guardrail system also includes posts that are commonly fabricated from steel. These posts are often pre-drilled by the manufacturer and include the hardware for installation. Standard galvanized steel systems (specifically 12-gauge) provide durability and are often fabricated in curved, 90 degree variations, for traffic areas. Other variations include cylindrical steel rails and flatter rails, featuring ribbing. For indoor and outdoor areas, railings are typically painted OSHA yellow. The type and quantity of intermediate rails varies according to the application requirements. For instance, a railing can consist of one to three rails and the rails may be coated with UV resistant polyurethane sleeves.[1]

The guardrails are produced as cable barriers, steel barriers, two and three-wave guardrails. Cable barriers have great importance on bridges, coast and the gateway. Cable barriers are produced in accordance with international standards steel, ropes and fittings. Superior corrosion resistance is provided with hot dip galvanizing. Productions are done in accordance with KGM (General Directorate of Highways) specifications and RAL- Rg 620 standards with high technology machines and equipments. The barriers and guardrails must be St-37 steel and superior corrosion resistance is provided with hot dip galvanizing.[2]

Guardrails were being used for the first time in Germany. Guardrails, metallic corrosion-resistant high-security guardrails developed in the United States, prevented the loss of life of tens of thousands. Several international standards have been developed for the production and installation of guardrails, such as EN1317, RAL, and RC6120..[3]

Automotive safety[edit]

Further information: Traffic barrier
A truck crashed through the central barrier of a German freeway (A24).
A removable guardrail as median barrier

In traffic engineering, guardrails prevent vehicles from veering off the roadway into oncoming traffic, crashing against solid objects or falling into a ravine. A secondary objective is keeping the vehicle upright while deflected along the guardrail. The problem with this is that a guardrail of the optimum height for a car might not keep a truck from toppling over it, while a motorbike might slip under a higher rail.

In most cases guardrails would not be able to withstand the impact of a vehicle just by the strength of the individual posts in the area hit by the vehicle. Instead, the guardrail is effectively one strong band that transfers the force of the vehicle to multiple posts beyond the impact area or into a ground anchor at the end of the guardrail. Newer concrete barriers, while usually strong enough to withstand direct hits by cars, still work on a similar principle in deflecting heavier vehicles such as trucks.

Though they have usually prevented far more serious accidents, guardrails have frequently ranked as among the highest sources of injury and fatality in a fixed-object crash.[4] Among the primary reasons for this is the type of treatment used at the end[5] of the guardrail facing oncoming traffic. Most end designs will either deflect, absorb, or launch the vehicle.

Deflection causes the vehicle to be redirected back into traffic – particularly dangerous on undivided roadways, as the vehicle may travel into oncoming traffic. Deflection is prevented in modern installations by allowing the guiderail to deform under the load of the crash, giving a 1.5 metre capture zone behind the guiderail. It is important that the grades and fixed objects behind guiderails protect this clear zone, allowing safe capture of the vehicle by the guiderail. If the guiderail is too rigid to deform, deflection may be an issue.

Absorption is when the force of impact is directly transferred between the vehicle and guardrail, which may cause the end to puncture the vehicle. This is most common where a "whale tail" or blunt end treatment exists. To mitigate this a number of guiderail end treatments exist such as "Extruder end treatments", "eccentric loaders" and "Driveway wrap treatments" which result in blunt ends rarely being left exposed in modern installations.

Lastly, a vehicle can become airborne upon striking a guardrail with a buried end treatment, which may negate the purpose of the guardrail, if the vehicle continues beyond the guardrail and strikes the object the guardrail was protecting. Additionally, an airborne vehicle is likely to collide in a manner that the vehicle was not designed for, increasing the risk of failure in the vehicle's collision safety systems. Collapsible guard rails are safer than rigid ones, since a longer collision duration will result in a smaller average impact force.

Transportation engineers limit the guardrails as much as possible, as guardrails should only be placed when the roadside conditions pose a greater threat than the guardrail itself. In fact, in the hierarchy of five roadside safety treatments, shielding with guardrails ranks fourth. Therefore, while guardrails are often added as a retrofit to existing roads, newer roads are designed to minimize roadside threats, whether that may include aligning a road on a smoother curve or filling in a ravine which would eliminate the need for guardrail altogether. In addition to new research into end treatments, public awareness among both drivers and engineers has been gradually reducing injuries and fatalities due to guardrails.

There are four general types of guardrail, ranging from weakest and inexpensive to strongest and expensive; cable and wood posts, steel and wood/metal posts, steel box-beam, and concrete barriers. While cheaper guardrail is the weakest, often being destroyed from the impact of a light vehicle, it is inexpensive and quick to repair, so this is frequently used in low-traffic rural areas. On the other hand, concrete barriers can usually withstand direct hits from vehicles as heavy as trucks, making them well suited to high volume routes such as freeways. While rarely damaged, they would be considerably more expensive and time-consuming to repair. Concrete barriers are frequently installed in the median, being expected to withstand frequent impacts from both sides, while the shoulders of the road often have cheaper guardrail.

Guardrails are sometimes placed beneath the sides of high-sided heavy vehicles (such as lorries, semi-trucks, etc.). to prevent smaller vehicles from passing underneath the heavier vehicle during a collision and being crushed.

Street railings as hindrances and dangers[edit]

In cities such as London where pedestrian railings are installed at the sides of roads, many cyclists have died when crushed against them by motor vehicles.[6][7] In addition railings have been found to increase the chances of injury to pedestrians for a number of reasons including increasing the inattention of both drivers and pedestrians.[8] For these reasons some councils in the United Kingdom have removed pedestrian railings.[8] This was after London's Royal Borough of Kensington and Chelsea did so and found that the rate of injury to pedestrians decreased three times faster than elsewhere in the city.[8]

The removal of pedestrian railings on streets is an example of the shared space concept in urban design.

Railways[edit]

Railway trackage has guard rails (aka check rails) for at least 2 general reasons: first to guide wheels through possible catch points on turnouts or diamonds. Similarly, guard rails may be installed inside the innermost running rails on very sharp curves. The other most common usage is to prevent damage to other structures, especially bridges, in a derailment.

See also[edit]

References[edit]

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