Chapter 8. Barriers and motorcyclists The purpose of road safety barriers and guardrails is to protect the road users from hazards on the roadside when an adequate clear zone cannot be provided. Barriers are also installed in the middle of the central reservation of roads to prevent head-on collisions. The installation of barriers presents a new hazard to motorcyclists, who are at greater risk of fatality and serious injury in the event of a collision with the barrier. According to Fredriksson et al. (2015), the best barrier for a motorcyclist is “no barrier at all,” and if the barrier itself is more dangerous than what it is designed to protect, no guard rail should be installed (71). Since there are bridges, trees, steep mountain roads, culverts or gullies, oncoming traffic and other obstacles in the road environment, there will always be a need for barriers to protect road users. For motorcyclists a barrier is never completely safe since they do not benefit from the protection of the bodywork and passive safety systems offered by a passenger car. The best solution is to ensure that barriers, where they are needed, are positioned further away from the road lane (to allow for an adequate safety zone) and are of a design that does not pose undue risk of injury to a motorcyclist. 8.1 INJURY AND FATALITY RISK Barriers are common obstacles in fatal motorcycle crashes. Research from around the world dating as far back as the 1980s has consistently showed that barriers pose a much higher risk of injuries and fatalities compared to other road users, including that: They are designed and installed with cars and heavy vehicles in mind. Road restraint systems are a factor in 8 to 16 percent of motorcyclist deaths (72, 73). Motorcyclists are 15 times more likely to be killed than a car occupant in barrier collisions (74). The injury risk of off-road crashes with a barrier is twice that of crash where the motorcyclists do not collide with a barrier (76). Motorcyclist injuries can be up to five times more severe in a barrier collision than if the rider had hit the rigid object that the barrier was guarding against (74, 75). US data shows that one in eight motorcyclists who struck a guardrail were fatally injured which gives a fatality risk that is 80 times higher than for motorists (77). The injury risk increases by 200 % in off-road accidents compared to a crash where the rider doesn’t collide with a barrier (76). American data shows that one in eight motorcyclists who struck a guardrail were fatally injured which gives a fatality risk that is 80 times higher than for motorists (77). More recent US data from 2018 showed motorcycle riders accounted for 40% of all fatalities resulting from a guardrail collision and that motorcyclists are highly overrepresented in the number of fatalities in guardrail crashes terms of fatalities per registered vehicle. Cars compose about half of the vehicle fleet (46%) while motorcycles comprise only 3% of the registered vehicles (78). A 2015 comparison between the car and motorcycle fleet in traffic compared to fatality data shows that the risk for a fatal crash with a barrier in Sweden is 27,7 times higher for those riding a motorcycle compared to those who are traveling in a car (71). An online survey in 2019 of 1,578 motorcyclists from 30 different countries who had been involved in a crash found that four percent (n=57) of the respondents crashed with a barrier (83). The percentages crashing into roadside barriers were lower compared to other studies, which might reflect the survey method (since self-reported crashes cannot include those with fatal outcomes or severe neurological injuries) or the lower presence of roadside barriers in the countries of the survey respondents (83). 8.2 CRASH SEQUENCE Studies of motorcyclist collisions with barriers show that motorcyclists collide with barriers in different ways. In approximately half of the crashes, the motorcyclist was sitting on the motorcycle upon collision with the barrier. In this case, there is a risk that the motorcyclist is thrown over the barrier. In the other half of crashes, the motorcyclist was sliding on the ground into the barrier having fallen from their vehicle. The risk for a fatality or serious injury is higher when a motorcyclist is sliding on the ground and collides with the poles of the barrier. Studies of collisions with barriers in different countries show that the collisions occur at angles less than 15 degrees. (79, 80, 81) For example, of 78 surveyed fatalities in Australia, the average angle was 15.4 degrees, and the average speed of the motorcyclists upon impact was 100.8 km/h. The average distance from impact to stop was 28.9 meters for a seated motorcyclist, 26.3 meters when the motorcyclist scraped, rolled, or slid along the guardrail top and 12.7 meters for the motorcyclist who slid along the ground (82). 8.3 WHERE DO MOST BARRIER COLLISIONS OCCUR? Motorcycles are especially vulnerable to collisions on bends and curves, where acceleration or deceleration occurs, or where the stability of the motorcycle is at stake and loss of control is more likely. A disproportionately high number of impacts happen on exits with a tight radius and on roundabouts (84). The highest risk for motorcyclists colliding with barriers are in tight and long curves (85, 86). The high risk in curves is the main reason behind the decisions and legislation in different countries for general guidance for when and where to install MPS (Slovenia, Portugal, Germany, Austria, France, Spain, Norway). Fatality data from Sweden is however different to the rest of Europe and Australia. Over half 55 of the fatal barrier collisions took place on motorways and 2+1-roads. These are mainly straight roads with a speed limit of 100-120 km/h with median and side barriers installed close to the road edge on both sides (87). 8.4 DIFFERENT BARRIER TYPES Common barrier types are the w-beam, cable and concrete barriers. There are other different barrier types which may be specific to some countries and design specifications. For example, ellipse and pipe barriers are often used in urban areas on bicycle roads and on bridges for aesthetic reasons (88). Due to the type of impact of a motorcyclist and the lack of protections, barriers need to be as smooth as possible and with no sharp, aggressive surfaces to reduce the injury risk in motorcycle crashes. W-beam The most common barrier in the world is the post and rail barrier, frequently known as ‘w-beam’. This type of barrier consists mainly of a horizontal steel beam held in position by vertical posts fixed to the ground. Typically, single sided barriers are used on the road shoulder and symmetrical, double-sided guardrails are used in the central reserve. For motorcyclists who crash into the barrier, although the beam itself presents a smooth, relatively unaggressive surface, the rigid, vertical posts are relatively aggressive as they result in concentrated impact loading at the collision. They are most often made entirely of steel but can also include timber components or cladding. Barrier height varies between countries as well as the use of a block-out to offset the horizontal barrier from support posts when installing the barrier. A w-beam barrier with a block-out gives a better chance to install MPS below the beam, providing the distance to the ground is high enough. Cable barriers A flexible cable barrier frequently known as wire-rope barrier, consists of long lengths of horizontal, pre-tensioned steel cable, held at the desired height by posts that rest on the ground. These systems are designed to restrain with relatively low levels of deceleration – however, their flexibility means that a relatively wide area is needed. The cable represents a potential source of concentrated impact loading for a motorcyclist in contact with it, although the cable is relatively flexible. The cable is often seen as major potential risk of severe abrasions to motorcyclists (132), however there are currently still diverging views about how hazardous the cable is. The posts do not represent the same rigid obstacle to motorcyclists as guardrail posts do. On the other hand, the post extremities, and any protrusions, such as hooks and sharp edges, are hazardous if left exposed as they can cause snagging of body parts resulting in serious injury. Also, it is not possible to fit motorcycle protection on cable barriers. Cable barriers are commonly used in some countries, for example Sweden and Australia but are not used at all in other countries. Installation of cable barriers is prohibited in for example Ireland, Norway, Germany, and the Netherlands. Concrete barriers Concrete barrier can be composed of modular elements linked together or can be cast in place on the road surface or verge. They are used on the verge and in the central reserve of roads and modular systems are commonly installed temporarily to protect work zones. Concrete barriers can be rigid or, in the case of unanchored, modular systems, less rigid. However, due to their weight they remain rigid from the point of view of an impacting motorcyclist although they present a smooth impact surface. Various accessories (e.g., signposts, reflectors) are often fitted to road safety barriers after their installation. The possible risk to an impacting motorcyclist should be considered when planning the use of such accessories. 8.5 THE INJURY RISK FOR DIFFERENT BARRIER TYPES Several US studies by Gabler et al. found that the risk of being killed in collision with a W-beam barrier is 12 percent, compared to 8 percent for a concrete barrier. The studies found no significant difference in collision with a cable barrier compared to the W-beam barrier (96, 97, 98). Whatever the barrier types, the presence of rigid protrusions and sharp edges is hazardous for impacting motorcyclists. In general, it is the barrier poles, not the longitudinal barrier beams that causes the most serious injuries on the motorcyclist. Smooth barriers without unprotected posts and protruding parts, provide less risk of injury (89, 90, 91). In a collision where the rider is sitting, sharp edges and corners as well as posts sticking up over the barrier have a major significance for the outcome of injuries. The cutting and snagging effect are common in collisions with cable barriers and W-beam barriers (87, 92, 93, 94). A Swedish study of 20 typical motorcycle crashes against various barrier types showed that the rider was sitting on the motorcycle at most collisions which resulted in injuries on legs and feet. Head, neck, chest and pelvis injuries dominated in the fatal crashes. In the most severe crashes, limbs were torn off. The motorcyclists had been caught in the barrier in all fatal barrier collisions (93). The distance between the barrier and the edge of the road is important. An increase in the distance between the barrier and the road edge (median and side) showed a reduction in both crash and injury risk for all crashes. The average reduction in crashes is between 1,9 – 5,1% per meter increase of distance (102, 103, 104). The height of a barrier can also determine the severity of motorcyclist crash outcomes. A Norwegian study (101) concluded that a low barrier increases the risk for motorcyclists of falling over it in case of a crash and hit the object it is intended to protect the road users from. An American study identified the traffic barrier height as one of the most significant variables impacting the severity of box beam barrier crashes. The injury risk would be higher if the barrier was below 63 cm compared to if it was higher, 63-79 cm (101). Accessories such as signposts or reflectors fitted to road safety barriers after their installation have the potential to cause further injury risk for motorcyclists in the case of a crash. 8.6 MOTORCYCLE PROTECTION SYSTEM, MPS Motorcycle Protection System, MPS is an element of roadside infrastructure designed specifically to reduce run-off-road crash severity for motorcyclists or other powered two-wheelers should a safety barrier be struck, or to protect motorcyclists from more severe hazards such as cliffs, trees or poles. It can also prevent head-on collisions from a fallen motorcyclist sliding under a median barrier into the path of on-coming traffic. MPS may include: Additional rail on the lower section of the standard road safety barrier system (under-run). Frangible/lower strength posts. Energy absorbent post covering and Device to remove sharp edges from barriers (105). According to all tests carried out and available research, barriers with MPS gives a lower risk of injury, whether the rider slides into the barrier or is sitting on the motorcycle (94, 106, 107). Most commonly, steel guards, mesh systems or plastic tubes that are fitted below the existing safety barrier, preventing riders from sliding under the barrier beam element and offering protection from the steel support posts. This is known as ‘continuous MPS. MPS protects riders from the barrier posts, it absorbs kinetic energy, it allows riders to decelerate more slowly and redirect them along the barrier. MPS is meant to prevent a sliding motorcyclist to crash with the posts. It also reduces the injury risk where the riders are sitting on the motorcycle since body parts are not caught in or between the poles or caught by protruding parts on the guardrails. Discontinuous MPS or Motorcyclist Impact Padding (MIP) refers to protection around the individual poles. For this reason, it is a significantly less effective measure of ensuring safety for motorcyclists but can be useful where continuous MPS is not possible. For example, MIP is installed in Slovenia on existing or new guard rails on curves where due to the geometric elements of the road it is not possible to develop greater speeds (sharp curves and serpentines). It is also used in conjunction with the continuous MPS for exposed posts and barrier terminals rails, where they cannot be installed in their full length due to the end elements, and it is not possible to protect the supporting post in front of the beginning of the motorcyclist barrier (38). However, results of simulations in Slovenia shows that only continuous MPS provides sufficient protection for a human body. Yet there are no MPS devices to protect motorcyclists from protruding parts on the top of the barrier, although some designs have been proposed, including System Euskirchen Plus (EDSP). The Texas A&M Transportation Institute is undertaking a project in 2023 for the development and full-scale crash testing of an improved railing system for use on top of barriers (108). 8.7 INSTALLATION OF MPS – WHERE AND WHEN? Whilst there is no country which demands that only barriers with MPS are installed, several countries have implemented national laws and guidelines requiring their consideration. In France there has been a national regulation requiring the use of MPS on guardrails in high-risk areas since 1999. Portugal was the second European country to introduce this in 2004. Other countries have introduced similar rules for the installation of MPS in particular areas since then. A report from FEMA in 2012 gave examples about where and when MPS should be installed. The report describes alternative solutions from European countries to identify the most critical road sections for installation of MPS. MPS is suggested on: External/outside shoulder side of highways where the radius is equal to or less to 400 meters, On other roads in the external side of bends with a radius equal or less to 250 meters, Deceleration lanes on exits, on single carriageways with shoulder over 1.5 meters when the radius is lower than 250 meters and, On any other highway with a speed reduction at curve higher than 30 km/h. The location for installation of MPS in the Netherlands are defined in a simple decision tree (Annex 2). which includes provisions to identify a site for MPS in the short term, medium term and no action for now. In Germany roads are identified as motorcycle roads after an investigation in several curves with a radius under 180 meters. These roads are prioritized for MPS installations (109). Some German Federal States have implemented investment programs during the last years to retrofit existing guardrails with MPS on roads with extensive motorcycle traffic. Portugal states that MPS must be placed on all roads wherever necessary. An Australian based technical guide (110) identifies and prioritizes where MPS should be provided based on curve radius, road alignment, lane width surface condition and available sight lines and stopping distances. It also provides design guidance to hazardous end terminals to be installed outside of an errant motorcycle’s impact zone. A new handbook for safe roadsides and road equipment was released in Norway in December 2022 stipulates that MPS are installed on outer shoulders on both new and existing roads depending on curve radius, on locations where there is a high risk for motorcyclists to crash and collide with barriers. Barriers with protruding parts and sharp edges are not allowed on roads with a great need for motorcycle safety and protection (111). The Slovenian guidelines for motorcycle safety recommends MPS on curves with certain radius for roads with high motorcycle traffic (200 per day) or at least four motorcycle crashes the last three years (38). 8.8 MAINTENANCE OF BARRIERS WITH MPS Once MPS are deployed, it is important to check and maintain them. In many cases, the presence of excessive vegetation or accumulated soil or leaves can hinder the proper deflection of an MPS during impact which can have negative consequences for its performance. The Swedish Transport Administration installed MPS protection in 2012 and monitored their resistance to damage due to maintenance. While the evaluation found that no damage in winter, there was an accumulation of debris, gravel and leaves on the ground against the side of the road which requires increased maintenance compared with barriers without MPS (120). The Slovenian guidelines has a chapter about the need of maintenance before installing MIP as well as regular inspections and maintenance after the installation (112). Since during impact the MPS interacts, in some way, with the barrier to which it fitted, it should not be assumed that one MPS will function correctly on any barrier. Therefore, it is important to assess the performance of an MPS fitted to each type of barrier on which it will be deployed. 8.9 MPS TECHNICAL SPECIFICATION In the late 1990s, a test protocol for MPS to be fitted to barriers was developed in France by the LIER test center and INRETS, the French national transportation research institute. Defined based on French accident data, the test method consisted of two impacts with an instrumented crash dummy sliding along the ground and impacting the MPS. The protocol was used in France to evaluate MPS for steel guardrails and as a basis for the approval of systems for use on the French road network. Several years later, the Spanish national standard, UNE 135900, for MPS testing and evaluation was developed, subsequently coming into force for the approval of MPS to be installed on Spanish roads. The Spanish standard took the French test method as a basis and developed it further, changing one of the test dummy test impact configurations, considering the evaluation of discontinuous MPS (localized protection of barrier posts rather than a protective device running continuously along the guardrail), and adding a second, higher test impact speed. Subsequently, requirements for MPS evaluation were also introduced in Italy and Portugal, both based on the sliding dummy test configurations previously adopted in France and Spain. In Germany, the BASt developed a test protocol for the evaluation of MPS in the case of a motorcyclist impacting the system upright whist still on the motorcycle. At the request of FEMA, CEN agreed to undertake the development of a standardized, European test method for the evaluation of MPS for barriers. To deliver a test method as soon as possible, and to avoid undermining the existing various national regulations, it was decided to build on the existing sliding rider test configuration with the possibility of adding an additional upright configuration in the future if this was deemed necessary. The resulting test method, CEN/TS 1317-8, was published in 2012 and was later redesignated CEN/TS 17342, Road restraint systems – Motorcycle road restraint systems which reduce the impact severity of motorcyclist collisions with safety barriers which is the only internationally approved evaluation protocol for MPS, and it is used in Europe, Australia, and New Zealand. Despite its availability since 2012, the use of this assessment method, and of the existing alternatives, remains limited. The specification contains performance classes, impact test acceptance criteria and test methods for barriers where the test dummy is in a sliding position. The protection systems are those fitted to barriers or barriers that have an inherent rider protection or risk reduction capability. For systems designed to be added to a standard barrier, the test results are valid only when the system is fitted to the model of barrier used in the tests since the performance will not necessarily be the same if the system is fitted to a different barrier. CEN/TS 17342 has its limitations. The crash test dummies (correctly known as anthropomorphic test devices) are also limited for simulating the human body impacts of motorcycle crashes. There is no crash test dummy yet developed or validated for use in the type of impact configuration required for MPS testing. Furthermore, the test method in CEN/TS 17342 does not specify a thorax injury criterion, despite studies showing that the thorax region of motorcyclists had the highest incidence of injury in barrier crashes (82). According to Bambach et al, a quarter of the motorcyclists crashed with the barrier in an upright position with the rider sliding and tumbling along the top of the barrier. Others, like Berg et al. (92), Grzebieta et al (98) and Rizzi et al (95) mention a higher number. In a FEMA study of 2018 (114) the conclusion was that most crashes occur when the rider still sits on the motorcycle. Thus, an additional test should be developed, which requires the rider to be in an upright position when striking the barrier and then slide along the top of the barrier (82). Additional tests are also required for types of impacts not currently covered, particularly for barrier crashes where the motorcyclist is in an upright position and then slides along the top of the barrier (82). This would be helpful in the development, testing and commercialization of new MPS for the top of roadside barriers (such as EDSP). Despite its limitations, there are no doubts that MPS that have been approved as a result of testing, have saved lives and reduced injuries to motorcyclists who have crashed with the MPS, both sitting on the motorcycle and sliding on the road when colliding with the barrier. Possible solutions There is a need for investment in the development of protection systems and evaluation protocols for the motorcyclist crash mode in which the motorcyclist collides with the roadside barrier in the upright position. However, without a crash test protocol to assess MPS for reducing such injuries, there is currently no mechanism to develop, test and validate such systems. Several countries have made notable steps towards developing MPS for top protection to guardrail systems, such as the successful studies noted previously in Germany (Euskirchen Plus), the Texas A&M Transportation Institute and VTI, Linkoping, Sweden. Testing methodologies developed in these studies may be useful in establishing testing protocols for the upright crash mode, which could potentially be included in international specifications or standards for roadside barrier testing. A valuable tool in the development and evaluation of MPS and barriers that are more motorcyclist-friendly is virtual testing using computer simulations (Annex 2). This allows MPS and the test dummies used in physical crash testing to be modelled allowing so-called virtual tests to be performed. The use of virtual testing for the development of MPS, and to some extent for the validation of systems on a national basis, has been developing over recent years and its use as an additional evaluation tool should be considered in the future (102). 8.10 NATIONAL LEGISLATION MPS is required systematically on guardrails in high-risk locations on the French road network since 1998. Portugal, Spain, France, the Netherlands, Germany, Norway, Slovenia, Austria, and UK (115) have also introduced requirements for MPS although the requirement remain quite diverse. For example, in Australia there is no requirement for MPS, but technical guidance presented in 2020 defines MPS and provides a decision process tree for where and how MPS should be installed (105). As a technical specification, the use of CEN/TS 17342 is entirely voluntary. Upgrading the TS to a full European Standard would mean that any CEN member state requiring the assessment of MPS would be bound to assess based on the method defined by the European Standard. International uniform assessment methods would encourage the development of MPS. Possible solutions Write a ‘general’ European specification matching EN1317 and CEN/TS 17342 that can support authorities to have proper technical national laws and specifications on motorcycles and barriers. Promote a standard or specification which is based on computer simulations beside real life tests to enable MPS to be installed on different barriers. Promote road authorities to adopt these general guidelines until there is a proper standard for MPS. 8.11 COST OF MPS A common argument for using MPS to make barriers safer for motorcyclists is the increased costs. The cost to buy land and clear the roadsides is higher compared to an installation of a roadside barrier. Installing MPS can result in higher investment costs in road construction and upgrades. Adding MPS on a w-beam barrier in Sweden 2023 increase the cost from €40 per meter to €60 per meter. The cost in Sweden for concrete barriers per meter is €175 (121). National legislation requiring routine installation of MPS would improve the predictability of market demand for MPS products, which would likely reduce costs (121). 8.12 RECOMMENDATIONS TO REDUCE THE INJURY RISK IN COLLISION WITH BARRIERS When decisions are made about the choice of barriers and roadsides are made it is crucial to include the needs of motorcyclists to minimize the injury risk, since there are no compulsory test protocols that demands safe barriers for motorcyclists. These solutions are based on global existing knowledge, research and statistics presented above and checklists in use (Annex 1). Don’t install a barrier if the barrier itself creates a higher injury risk compared to what it is supposed to protect the road users from. If possible, create forgiving roadsides instead of side barriers. Include motorcycles in the planning stage. Include motorcycle safety when choice of barrier is made, use checklist, and include legal demands and regulation. Include motorcycle safety when the decision is made of the distance between barrier and road edge. Include demands for a hard paved shoulder between the road edge and barrier. Choose the right barrier when roads are built and rebuilt. Include the Life Cycle Cost (including investment, maintenance, and socio-economic costs) when the choice of barrier is made. Include a block-out on w-beam barriers which will increase the possibility of adding MPS at a later stage. Choose a smooth barrier without protruding parts on the side and top where motorcyclists can’t get caught. Choose a barrier with a height that minimize the risk of falling over and hit the obstacle the barrier is protecting road users from. Use crash data to find out where to install the barriers which minimize the injury risk. Use barriers with MPS in curves and at high-risk locations. Use rumble strips instead of median barriers on narrow roads. When a median barrier is installed, choose the barrier that not only prevents from head-on collisions but only presents the minimum injury risk in collisions for all road users, including motorcyclists. Investigate the possibility of earth berm instead of barrier. EXECUTIVE SUMMARY CHAPTER 1. INTRODUCTION CHAPTER 2. MOTORCYCLE SAFETY IN FIGURES CHAPTER 3. GLOBAL, REGIONAL AND NATIONAL GUIDELINES ON MOTORCYCLE SAFETY CHAPTER 4. WHERE DO MOST INCIDENTS AND CRASHES OCCUR? CHAPTER 5. ADDRESSING MOTORCYCLE SAFETY CHAPTER 6. ROAD SURFACE FRICTION CHAPTER 7. THE NEED FOR ROADSIDE SAFETY ZONES CHAPTER 8. BARRIERS AND MOTORCYCLISTS CHAPTER 9. GUIDANCE BEFORE CURVES CHAPTER 10. RECOMMENDATIONS APPENDIXES REFERENCES TERMINOLOGY AND ACRONYMS WORKING GROUP INFORMATION Download the report as a pdf file. Share on Facebook Share Share on TwitterTweet Share on Pinterest Share Share on LinkedIn Share Share on Digg Share Send email Mail Print Print
