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Evaluation criteria of Vehicle Restraint Systems

Despoina Drymalitou, Transportation and Infrastructure Dipl. Engineer,

Member of WG1 and TG2/TC226/CEN E-mail: drymalit@otenet.gr

Abstract A large number of certified restraint systems are available in European market, albeit having different structural properties. Consequently a selection process that conforms to the performance levels stipulated in a study and takes into account the differences in structural properties of various systems, is crucial for investment decisions both in terms of capital cost and maintenance cost. The most pertinent questions arising during the selection process are related to:

− The sources of reliable information concerning restraint systems − The type(s) of technical information required to form a complete picture of restraint

systems − The evaluation criteria to be adopted for selecting the appropriate restraint systems

to apply.

Keywords: Standard EN 1317, OMOE-SAO, Vehicle Restraint Systems, Evaluation of Restraint Systems, Basic Requirements, Road Safety. 1. Introduction The development and adoption of new national Guidelines for the Vehicle Restraint Systems (OMOE-SAO) [3] and Norm 17 [9] were the first significant step towards the alignment of the National Regulatory Framework referring to the restraint systems with the harmonized standard EN 1317 [1] and marked the beginning of the implementation of this standard in Greece. The implementation of the standard EN 1317 and of the harmonized with this OMOE-SAO is an essential prerequisite for the improvement of road safety levels in Greece. But the restraint systems besides the fact that in principle should have been successfully tested in accordance with the standard and bear the CE marking, should also fulfill and some other criteria. It is important for road safety, the systems selection criteria to be based on their availability, quality, construction, repair and replacement. Thus it will be possible the signing of contracts with those involved in the implementation of road construction projects, which will contribute to an economical and technically feasible outcome. For example the selection of restraint systems that are different structurally, is not effective. During the preparation of designs in accordance with OMOE-SAO [3] and particularly of detailed designs, it was found that in general the evaluation criteria and consequently the selection of certified restraint systems are their weight and the information available from their distributors. Because the aforementioned criteria lead to uneconomical and non-functional solutions with respect to the maintenance, it is necessary for both the national authorities and those involved in the implementation process of the road works, to be systematized:

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− the technical information that fully describes the certified restraint systems in order to allow a direct comparison between the different systems and

− the criteria for a further evaluation of restraint systems in conjunction with their technical features and the road construction details such as verge width, paved shoulders etc. at systems installation location in order to: Avoid the numerous types of restraint systems. Select the appropriate restraint systems in relation to the roadside configurations

and the particularities of the road sections. Achieve homogeneity. Organize and systematize the maintenance in a simple and effective way. Reduce of cost not only during the implementation of the studies but also during

operation and maintenance of road works. 2. Description of Vehicle Restraint Systems (VRS) The only reliable source of information regarding the certified restraint systems are the installation manuals, which constitute the technical specifications of every system. These include the description of the system and all the related drawings and information according to EN 1317-5. These manuals are official documents, which accompany each system and are approved by the Notify Body, according to the Declaration of Performance (DoP) of the manufacturer. 2.1 Safety barriers For the safety barriers applies the standard EN 1317-2 and the relevant rules for products CE marking. In order to fully describe a safety barrier, beside its name, the following information is required: (1) Drawings of the system. (2) Performance under vehicle impact, i.e. containment level, working width class and impact

severity level. (3) Installation method, i.e. piled in, on structure, anchored on stiffening plate etc. (4) Test length L1. (5) Design of the system, i.e. whether it is single sided or double sided. (6) System material, e.g. steel, concrete. (7) System width of the system. (8) System weight. (9) Post distance. (10) Post cross section. (11) Quality of posts material. (12) Post length. (13) Beam cross section, i.e. 2n or 3n beam. (14) Beam or concrete quality, e.g. S 355JR, C30/37. (15) Beam thickness. (16) Notes concerning installation of the system, etc. The above mentioned are summarized in Table 1.

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Table 1: Overview of safety barriers

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Table 2: Overview of transitions

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2.2 Transitions For the transitions applies the standard ENV 1317-4. Thus certification of transitions until today is optional. Despite this fact, there are systems available in the market, which have been successfully tested and therefore their performance in case of an impact is known. Transitions are placed where safety barriers of different design and/or different mode of operation have to be correctly connected with each other according to their function. So it is important for road safety reasons, the choice of transitions, as much as possible, which have been successfully tested in accordance with standard EN 1317-2 with respect to the connected safety barriers. More specifically transitions from a flexible to a rigid system and vice versa, which have not been successfully tested, should be avoided. For a full description of connections in addition to their name, the following data are necessary: (1) The systems connected with the specific transition. (2) Drawing plan. (3) Test length/installation length L1. (4) Remark as to whether the system has been tested according to the standard or

not. (5) The performance under vehicle impact, i.e. containment level, working width

class and impact severity level. (6) The height of the system. (7) The weight of the system. (8) Notes concerning the connected systems, etc. The abovementioned can be presented in tables, similar to table 2.

2.3 Terminals For terminals applies the standard ENV 1317-4, with the consequence that their certification until today is optional. Despite this fact, they are systems available in the market which have been successfully tested and therefore their performance in case of impact is well known. In view of the forthcoming approval of the parts 5 and 7 of EN 1317, according to which it will also apply for the terminals the rules for CE marking, it is essential for reasons of road safety the choice as far as possible of terminals, which have been successfully tested in accordance with standard ENV 1317-4 combined with the respectively connected safety barrier. For a full description of a connection, beside its name, the following data are necessary: (1) Drawing plan.

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(2) Test length/installation length L1. (3) Reference of whether the system has been tested according to standard ENV

1317-4 or not. (4) Performance under vehicle impact that is performance class, vehicle exit box

class, permanent lateral displacement class, and impact severity level. (5) The system connected with terminal. The above mentioned are summarized in table 3. 2.4 Crash cushions For crash cushions applies the standard EN 1317-3 and their certification is compulsory. For a full description of a crash cushion, besides its name, the following data are necessary: (1) Drawing plan. (2) Shape, namely whether it is a parallel (P) or V-shaped (V) system. (3) The performance under vehicle impact, i.e. restraint level, permanent lateral

displacement class, vehicle redirection zone class (exit box), impact severity level.

(4) References on whether detached parts have been recorded during impact tests. (5) Taper angle. (6) System length. (7) System head width (Whead). (8) System base width (Wback). (9) System volume. (10) System weight. (11) Material quality. (12) Reference of whether the system is anchored on a concrete surface free of

cracks. (13) Reference on whether the system is possible to be anchored on an asphalt

surface. (14) Reference on whether the system is anchored onto a new concrete foundation

with foundation frame. (15) Minimum thickness of installation surface. (16) New concrete foundation quality. 2.5 Removable Barrier Sections (RBS) For the removable safety barrier sections (RBS) applies the standard ENV 1317-4, in which case their certification up today is optional. Despite this fact there are systems available on the market, which have been successfully tested according to EN 1317-2. Therefore their performance is known in case of vehicle impact. Given the requirements placed for passive safety on roads in accordance with the European directives and of the fact that after the approval of Part 4 of the standard the

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rules for CE marking will apply on these products, it is essential for reasons of road safety to choose as far as possible movable safety barriers, which have been successfully tested in accordance with standard EN 1317-2 combined with the relevant connected safety barriers. For a full description of a safety barrier, beside its name, the following information is necessary: (1) Drawing plan. (2) Whether it has been successfully tested according to standard EN 1371-2. (3) If it has CE certification. (4) The performance under vehicle impact, i.e. containment level, working width

class and impact severity level. (5) Test length L1. (6) Reference regarding the anchoring of system terminals. (7) System length. (8) System height. (9) The construction width of the system. (10) Planning width. (11) Opening length. (12) Weight of unit element. (13) Output per installation team/shift. (14) Existence of transitions. (15) Time need for opening and creating an emergency opening section. (16) Notes concerning the installation of the system, etc. The above mentioned may be presented in tables such as Table 5. 3. Evaluation criteria of certified restraint systems – Requirements The evaluation criteria for restraint systems are related to the requirements with which they should conform. There are two categories of requirements:

− Basic requirements, and − Requirements related to the installation location of the system.

The basic requirements that a system should fulfill, include: (A.1) The successful tests of systems according to standard EN 1317. (A.2) The modularity of systems. Installing modular systems helps to avoid the

implementation of piecemeal solutions, which are suitable only for specific situations. These kinds of solutions over time are becoming problematic with respect to the maintenance of systems. As modular considered those systems, which − consist of the same main components, − assembled of the same components with the exception of additional parts, − have the same name, − have the same working mechanism during impact, as well as combinations of different systems they are compatible with each other.

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Table 3: Overview of terminals

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Table 4: Overview of crash cushions

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Table 5: Overview of RBS

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Therefore, the systems to be selected should consist of the same components (beam, posts, spacers, deformation elements etc), and should have the same bolting system as well as the same working mechanism. For instance all the systems belonging to the same module should have beams with the same cross section, material and thickness. Respective uniformity will exist for the posts, the deformation elements etc. So can be achieved: − easy assembly, − easy replacement, warehousing and handling, − limited number of components, − no dangerous spots due to homogeneity of connections, − minimized number of transitions, − homogeneity on road sections, − minimized maintenance cost.

(A.3) The disposal on the market of transitions and terminals, which have been successfully tested according to the standard EN-1317, despite the fact that their certification until today is optional.

(A.4) The limited test length L1 of the system. Increased test length results in longer applications and thus cost of provision, installation and maintenance cost per running meter.

(A.5) The as possible small weight of the safety barrier per running m. Increased system weight results increased provision, installation cost as well as increased cost of bridges superstructure.

(A.6) The design of the system, e.g. dimensions, cross sections etc., in a way that the system does not have any sharp-edged component for road safety reasons. For example should be preferred systems with posts with C cross section instead of systems with post with U or HEA cross section.

(A.7) Detached parts should not have been recorded during the impact tests. These may cause safety issues, especially in areas where third parties are involved, e.g. a central reserve.

(A.8) The availability of systems descriptions, drawings, installation and maintenance manuals. These essentially are the technical specifications of each certified system. More specifically the installation manuals give guidelines for the installation that will achieve the performance declared for the Type Testing (TT), including details about maintenance and inspection. The use of the system relative to different ground and other conditions of installation and use, including limitations (e.g. allowed temperature range), should be defined by the manufacturer. The manufacturer guarantees and assumes responsibility for the installation conditions with the Declaration of Performance (DoP), according to Article 4, par. 3 of the EU Regulation No. 305 / 9.3.2011 of the European Parliament and of the Council (CPR - Construction Products Regulation) [6].

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Therefore the availability of this information facilitates the selection of the appropriate every time restraint systems in compliance with the conditions of installation area.

(A.9) The ability of manufacturers to train and certifying crews for the installation and maintenance of the systems. The installation of restraint systems should be performed only by certified crews, because the installation is part of the Type Testing (TT) and affects system performance.

The basic requirements that must be fulfilled by Crash Cushions relate to the following topics: (a) Mechanical resistance and stability:

− no detached parts which get loose or detached on vehicle impact − anchored on the underground

(b) Fire protection: − overall steel construction − no combustible parts, e.g. plastic.

(c) Hygiene, health and environmental protection: − overall steel construction, − fire galvanization, − nonflammable parts, − completely recyclable, − without toxic or harmful substances, − no form aggressive construction parts.

(d) Reliability: − laterally closed on all sides, − impact surface at only 10cm floor clearance, avoids that even motorcycles

run underneath, − the lifetime of the overall construction should be approx. 20 – 25 years

depending on the region where the products shall be installed. (e) Maintenance and care:

− maintenance free, − no inaccessible parts, − no construction parts get stuck, − no detached parts.

(f) Repair – friendliness: − all parts are easily accessible, − all parts are recognizable, − quick damage identification − short-term repair through pre- installed assemblies.

The requirements in relation to the system installation location include: (B.1) The suitability of the system for installation on the pavement edge line. (B.2) The impact severity level to be as possible A or B. (B.3) The probable "compatibility" of the systems with the existing MSO barriers.

For instance, if the certified systems have a beam similar to the existing barriers (beam with A cross section) or if some general similarities are

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identified, which might facilitate the connection of the existing barriers with the certified systems.

(B.4) The suitability of the system for installation in central reserve. (B.5) The suitability of the system for installation in lateral reserve. (B.6) The possibility of installing the system in narrow space conditions, for

example the availability of double sided safety barriers suitable for installation in central or lateral reserve.

(B.7) The installation ability of transition with an existing cast in place concrete barrier.

(B.8) The possibility of system installation in emergency openings of a central reserve.

(B.9) Reduced possibility of any detached parts of the system to entail a risk for third parties. In the opposite case it is not recommended to install such a system in areas such as the central reserve of motorways.

(B.10) The possibility of installing the system at the edges of bridges and retaining walls.

(B.11) The availability of safety barriers for installation on structures (bridges and retaining walls), which their load class is defined according to EN 1317-2 and classified according to EN 1991-2. It is noted that the load class for old certified systems is defined during impact tests or by mathematical analysis. The new systems on structures (OS) should be tested for the load class definition, in order to be considered suitable for installation at the edges of bridges and retaining walls.

4. Evaluation of certified restraint systems 4.1 Systematization of the evaluation of restraint systems The systematization of the evaluation based on the evaluation requirements and criteria may be according to table 6.

Table 6: Systematization of evaluation

x The requirement is fulfilled o The requirement is fulfilled under certain conditions, e.g. intermediate test length ˗ The requirement is not fulfilled a The relevant information is not available There is no area of application (e.g. system Ν2 in central reserve Η2)

4.2 Modular design (modularity) – numbering of modules In preparing the tables with the technical characteristics of the safety barriers a number can be given to each module. A module can contain more than one system.

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Every module should include only systems consisting of the same components and having the same working mechanism. The fulfillment of the requirements should also be evaluated for connecting elements or transitions that have been successfully tested (criterion A.3 of the basic requirements), because the transitions and their elements are a very important factor in the evaluation of the modular structure of a system. The manufacturers of a safety barrier, which constitutes part of a module, must declare with which other systems they can be connected and provide the drawings of connections/transitions. 4.3 Evaluation of basic requirements The fulfillment of the basic requirements will be evaluated as referred to in paragraph 4.1. It is desirable to be evaluated as "green" or at least as "yellow". It is not possible to evaluate with certain criteria some safety barriers, such as barriers on structures, which due to their required installation lengths according to OMOE-SAO, are not connected directly to terminal or transition. The test length and weight of safety barriers can be evaluated in relation to the containment level of each system according to table 7. On the basis of the above, the requirement for a small test length and weight of the safety barriers is evaluated with

− "green", when they are small, − "yellow", when they are medium, and − "red", when they are large.

4.4 Evaluation of requirements related to installation location The requirements related to the installation location of safety barriers should be evaluated where possible, with "yellow" or "green" as referred in paragraph 4.1.

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Table 8: Evaluation of Vehicle Restraint Systems

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Table 7: Evaluation of test length and weight of safety barriers

VRS Containment

Level

Test length L1 (m) Weight (kg)

small medium large small medium large

Ν2 ≤ 55 56 - 65 ≥ 66 ≤ 20 ≥ 21

H1 ≤ 60 61 - 70 ≥ 71 ≤ 30 ≥ 31

H2 ≤ 60 60 - 80 ≥ 81 ≤ 70 71 - 150 ≥ 151

H4b ≤ 85 ≥ 86 ≤ 75 75 - 150 ≥ 151

For example, a barrier with containment level N2 is suitable for installation at the outer pavement edge line of a road, provided that the criteria mentioned in OMOE-SAO [3] are fulfilled. But it is not suitable for installation in the central reserve, where the minimum containment level is H2 or at the edge of a bridge. Every safety barrier being in a module is evaluated for each individual criterion. The above mentioned are summarized in table 8. 5. Conclusions – Proposals From the foregoing results that the restraint systems to be selected should be modular, in order to avoid the implementation of piecemeal solutions, which are suitable only for some particular conditions. Lists should be prepared in accordance with the spirit of the aforementioned, with certified restraint systems in order: − to be available the information concerning the installation and maintenance of

restraint systems, − to be taken into account the evaluation criteria, that contribute to the

configuration of operational and financial solutions complying with the road safety requirements and

− to ensure that the specific systems are certified in accordance with EN 1317. These lists of restraint systems should include − their technical data, − their evaluation according to previous mentioned criteria, − their installation manuals, − their CE certifications, as well as − information regarding the certified manufacturers of the systems and should be revised every year by taking into account the rapid changes in the field of development and evolution of certified restraint systems. This way, − The numerous types of restraint systems are avoided. − The suitable restraint systems are selected considering the roadside

configuration (verges, central and lateral reserves) of the road sections, the

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location of road equipment such as traffic signs, etc. and generally the construction particularities of road sections.

− Homogeneity on road sections is achieved, i.e. maintenance logistics are easy. − The number of transitions is minimized. − Replacement, warehousing, and maintenance of systems are easy and simple. − It is possible to organize and systematize the maintenance in a simple and

effective way. − The maintenance cost of the works is reduced whilst at the same time the levels

of road safety are increased. References [1] European Standard (ΕΝ 1317), Road restraint systems

Part 1: Terminology and general criteria for test methods Part 2: Performance classes, impact test acceptance criteria and test methods for

safety barriers Part 3: Performance classes, impact test acceptance criteria and test methods for

crash cushions Part 4: Performance classes, impact test acceptance criteria and test methods for

transitions (under preparation; this document will supersede ENV 1317-4:2001 for the clauses concerning transitions)

Part 5: Product requirements, test and assessment methods and acceptance criteria

Part 6: Pedestrian restraint system – Pedestrian parapets (CEN/TR) Part 7: Performance classes, impact test acceptance criteria and test methods for

terminals (under preparation; this document will supersede ENV 1317-4:2001 for the clauses concerning terminals)

Part 8: Motorcycle road restraint systems which reduce the impact severity of motorcyclist collisions with safety safety barriers (CEN/TS)

[2] Einsatzftreigabeliste fuer Fahrzeug-Rueckhaltesysteme in Deutschland, BASt, (2013) [3] Road Design Guidelines (OMOE), Vehicle Restraint Systems (VRS), (OMOE-SAO),

(2010) [4] Richtlinien fuer passiven Schutz an Strassen durch Fahrzeug- Rueckhalt-systeme (RPS),

(2009) [5] RAL-RG 620 Fahrzeugruechkhaltsysteme an Strassen, Guete- und Pruefbestimmungen

fuer Systeme, Konstruktionen und Montage, (2009) [6] Official Journal of the European Union (OJEU), Construction Product Regulation

(CPR), (2011) [7] Official Journal of the European Union, (2009), Commission communication in the

Framework of the implementation of the Council Directive 89/106/EEC on the approximation of laws, regulations and administrative provisions of the Member States relating to the construction products, (2009/C 152/05)

[8] Mandate to CEN/CENLEC concerning the execution of Standardization work for harmonized Standards on CIRCULATION FIXTURES, Mandate M/111

[9] Circular 17/25/7/2011, "Implementation of the new Road Design Guidelines for Vehicle Restraint Systems (OMOE-SAO), (2011)

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Author

Despoina Drymalitou, holds a M.Sc. in Road Engineering. She has over thirty (30) years of experience in Design, Consulting Engineering and Project Management services in Transport Projects for highway designs, traffic signage, road restraint systems, road safety studies and preparation of guidelines for road design and road equipment in Greece. She is also active member as expert and delegate of Greece in

Working Group CEN/TC 226/WG 1 "Crash barriers, safety fences, guard rails and bridge parapets", for the Preparation and revision of EN 1317 Standard "Road Restraint Systems" and

Task Group CEN/TC 226/TG 2 for the Revision of EN 1317:5 Standard "Road Restraint Systems – Part 5: Product requirements, test/assessment methods and acceptance criteria for vehicle restraint systems".