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Guard rails, guardrails, railings or protective guarding, in general, are a boundary feature and may be a means to prevent or deter access to dangerous or off-limits areas while allowing light and visibility in a greater way than a fence. Common shapes are flat, rounded edge, and tubular in horizontal railings, whereas tetraform spear-headed or ball- are most common in vertical railings around homes. Inside the home, at the edge of stairs or balconies, they are called balustrades, especially when of a more elaborate design. Park and garden railings commonly in metalworking feature swirls, leaves, plate metal areas and/or motifs particularly on and beside .
High security railings (particularly if in flat metal then a type of palisade) may instead feature jagged points and most metals are well-suited to anti-climb paint.
A handrail is less restrictive on its own than a guard rail and provides support.
Examples of this are both architecture and environmental. Environmental guard rails are placed along where adjacent terrain is steep. Railings may also be located at scenic overlooks.
Guard rails in can be numerous, and are required by building codes in many circumstances. Handrails along may be supported by balusters forming a balustrade, and catwalks (a type of footbridge) and balcony are also lined with them. An example of a common residential guard rail (US) or handrail (Brit.) is a wood railing around a deck or patio. In the US this is typically built on-site from pressure treated lumber thus featuring a simplistic design of vertical baluster spaced every demonstrating compliance with building codes (standards).
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 are providing composite railing components. Wrought iron is another choice that is traditional and sturdy. Decorative examples are considered ironwork.
Building codes also require that no opening in a guard be of a size such that a sphere may pass. There are three exceptions according to the 2003 International Building Code Section 1012.3 which allow openings to not exceed depending on occupancy groups or special areas.
The architect Alvar Aalto imaginatively used handrails representing social stability. 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 and to prevent and .
As governments around the world courted the voting power of working people and trade unions in the 1980s, the health and safety rights of workers became of greater importance. This set the governmental procedures in motion that would see a flurry of regulations and legislation around workplace safety being introduced in industrialized countries in the 1990s. In the US and UK, these introductions, combined with the demonstrable success of the Occupational Safety and Health Act 1970 (US), and the Health and Safety at Work etc. Act 1974 (UK), led to workplace safety being taken more seriously at industrial facilities. Businesses worldwide began to see the value of effective workplace safety, in both the direct commercial sense of protecting assets, but also in the improved productivity levels of a protected workforce. Part of this increase in desire for industrial workplace protection, was a growth in demand for safety guardrails.
In the US, under OSHA Standard 1910.28(b)(15), employees who work on surfaces that are or higher off of the ground must have personal fall protection systems in place, such as handrails or guardrails. Great Britain's Work at Height Regulations 2005 by contrast apply to any work at height, defined functionally rather than quantitatively as any location, even at or below ground level, where a person could fall a distance liable to cause personal injury. Although the OSHA standard calls for a guardrail or guardrail system to protect workers on elevated work areas, current industry terminology would refer to that type of safety system as a handrail system or safety rail system.
The term "guardrail" as used in industry and distribution facilities refers to floor mounted systems consisting of horizontal rails attached to upright posts that resemble outdoor highway guardrail. The facility safety guardrails control in-plant vehicular traffic and protect areas where errant vehicle contact may cause harm to property or personnel. Common uses for guardrail systems may be along an aisle or building wall. Often guardrails are placed around equipment installations to prevent inadvertent contact from lift trucks. The guardrail provides a safety barrier preventing lift trucks or other in-plant vehicles from traveling into equipment, building walls, or personnel.
There are different types of "industrial" or "facility safety" guardrail systems, each with its own advantages.
Manufacturers produce several grades of steel safety guardrail. Each grade is suited to a different application which may be determined by size and type of vehicles used in the facility, the volume of traffic to be controlled, or the value/risk associated with the areas being guarded.
There are many types of polymer used in manufacturing safety guardrail. Polymer grains may be blended as part of the production process in order to enhance the natural properties of polymer in different ways. The most common types of polymer used are: polyethylene, polypropylene, and polyvinyl chloride (PVC). Using these types of polymer, there are three basic design philosophies for polymer guardrails:
The polymer impact dispersal safety guardrail design offers an advantage over steel guardrails. Steel guardrails, if impacted with sufficient energy, will permanently deform and require repair or replacement to the impacting vehicle, the guardrail itself, and even the floor substrate; whereas the impact dispersal safety guardrail design allows the guardrail to bend on impact, disperse the energy, and return to its original shape, resulting in no damage to the guardrail or the impacting vehicle.
In the US, there is no ANSI standard for testing guardrails. Steel guardrail system manufacturers test their systems to withstand impacts from a load moving at , whereas manufacturers of polymer safety guardrail systems rate and test their products at varying impact levels due to variation in guardrail product systems they offer, which can range from simple low impact energy pedestrian guardrail systems to high impact energy industrial traffic guardrail systems. In order to standardize testing for both steel and polymer guardrails, the Protective Guarding Manufacturers Association (ProGMA) industry group of the Material Handling Industry (MHI) trade association is currently working with ANSI to develop an industry endorsed testing and reporting standard.
The most common type of guardrail in use today is the blocked-out W-beam (strong post). Roadside Design Guide, 4th Edition 2011, AASHTO The strong-post W-beam guardrail consists of wood posts and wood blockouts or steel posts with wood or plastic blockouts. The wood or plastic blockouts reduce or minimize a vehicle snagging on the posts upon impact. In addition, a blockout may be used to increase the offset of guardrail with an obstacle such as a curb. The posts' primary purpose is to maintain the height of the guardrail during the initial stages of post deflection. Maintaining guardrail height also reduces the potential for a vehicle to vault over the guardrail upon initial impact. The posts also play a role in the amount of resistance and deflection a guardrail may experience during impact. Resistance in a strong post system results from a combination of tensile and flexural stiffness of the rail and the bending and shearing resistance of the posts.
One of the main concerns with strong-post W-beam guardrail has been the ability of the system to contain and redirect modern vehicles that have a higher center of gravity along with the increased weight of those vehicles. For instance the optimum height of the strong-post W-beam for a car might not keep a truck from toppling over it, while a motorbike might slip under a higher rail. To address these concerns, significant research and development of a system that could contain and redirect vehicles of varying weights and heights was developed and crash tested (both controlled and simulated). As a result, the Midwest Guardrail System (MGS) was developed and successfully crash tested per NCHRP Report 350 TL-3 criteria. The MGS has a higher mounting height, uses larger posts and blockouts as compared to the strong-post W-beam guardrail. One other significant difference is that MGS rail splices occur at mid-span compared to at the posts like the strong-post W-beam guardrail.
In most cases, a guardrail 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. Guardrailing functions as a system with the guardrail, posts, connection of the rail to the posts and to each other, and the end anchors (or terminals) all playing an integral role in how the guardrail will function upon impact. Soil conditions, height of rail, presence of curb or dike, weight of impacting vehicle, distance from back of post to hinge point and depth of post within soil can all determine how well the system will function upon impact.
A guardrail is effectively one strong band that transfers the force of the vehicle to the rail elements, posts, and end terminals or anchors. A run of guardrail must be anchored at each terminating end either by transitioning the rail into a fixed anchor such as a bridge rail or with an end terminal or end anchor placed in the ground or within an embankment. 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.
Guard rails are intended to deflect. The amount of deflection is dependent on a number of factors, some of which include the type and weight of impacting vehicle, height the guardrail is placed, type of soil the posts may be embedded within, length of embedment of the posts, and distance of the hinge point to the face of the guardrail are just a few. A guardrail that deflects significantly can causes pocketing, which has the potential to snag a vehicle, which may cause it to flip, roll, or cause the rail to fail entirely, allowing a vehicle to penetrate the guardrail.
Modern installations of guardrails are designed to allow the guiderail to deform under the load of the crash, and safely redirecting a vehicle back onto the roadway at a somewhat shallow angle. It is important that the approach grades to a guardrail system be very flat (typically 10:1 or flatter) and that grades and fixed objects behind guardrail be placed at a distance so that it will not affect the performance of the guardrail upon impact and deflection.
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 if the slope to which the end anchor is buried is relatively flat (3:1 or flatter), 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. A guardrail will have some give and deflection upon impact. The amount of deflection depends on many factors of which speed and weight of vehicle, type of guardrail installed, height of rail, length of posts, soil conditions and a number of other factors can all play a role. Guardrailing must be installed so that it is not so rigid that the rail will fail upon impact or the posts will snap off at the point where they are embedded within the ground.
Transportation engineers limit the amount of guardrail placed 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 obstacles, 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. Though they have usually prevented far more serious accidents, guardrails are considered roadside obstacles as well and transportation engineers must weigh whether placing a guardrail will reduce the severity of an impact as compared to what may be impacted if the guardrail were not placed. In general, the minimum length of guardrail with an end anchor at the trailing end and an end terminal on the approach end will be in length. An example would be where an overhead roadside sign structure is placed within what is considered the clear recovery zone—an engineer would need to determine that the structure has a potential to be impacted and the impact of a vehicle with that structure would be much more severe than impacting the guardrail.
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 a larger variety of vehicle types, making them well suited for use on high volume routes such as freeways or ramps with sharp curves. While rarely damaged, they would be considerably more expensive and time-consuming to repair. Jersey barrier 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. Although the use of concrete barriers on the right side of highway is becoming a much more frequent occurrence in areas where guardrail may be sustaining frequent impacts and the ability for maintenance repairs may be restricted by the general area or work windows due to high traffic volumes for most of the day.
The removal of barriers divorcing wheeled traffic from pedestrians is an essential of the shared space paradigm and philosophy in urban design. Security barriers have been introduced on a number of the world's major bridges and around key areas of congregation.
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