A concept study of an Alternative “ARMCO” trafficbarrier: A Systems Approach

Albert van der Merwe

Department of Industrial Engineering

University of Stellenbosch

267 Selborne Ave, Lyttelton Manor,

Centurion 0157

South Africa

+27 79 613 0000|15724050@sun.ac.za

Nico Treurnicht

Department of Industrial Engineering

University of Stellenbosch

Private Bag X1, Matieland,

Stellenbosch 7602

South Africa

+27 21 808 4448|nicotr@sun.ac.za

Copyright © 2012 by Albert van der Merwe and Nico Treurnicht. Published and used by INCOSE SA with permission.

Abstract South Africa has limited funding at provincial and district governmentlevels to provide road maintenance, including roadside barriers. This is due to the globalrecession and other socio-economic factors of a developing world country.

The local manufacturing industry is under constant pressure to develop innovative products orachieve economies of scale to be able to compete with local and international competition.

These two scenarios lend themselves toward synergy – If local industry can developinnovative products, for local conditions, at affordable prices, both challenges can beaddressed.

This study was undertaken to investigate the possibility of an alternative roadside barriercompared to current designs. Systems Engineering principles such as Requirements Analysisare used to develop the roadside barrier from a systems point of view.

1. BackgroundRoadside barriers are widely used around the world to restrain and redirect vehicles fromcolliding with opposite direction traffic and roadside hazards. These barriers are usuallymanufactured from reinforced concrete sections, braided steel cables or W-shaped steelbarriers (more widely known as “ARMCO” barriers). Figure 1, 2 and 3 indicate currentroadside barrier designs as implemented in the South African road network. Roadside barriersform part of the passive safety system of a road network.

Figure 1: Reinforced concrete barrierimplemented as road median. (The SouthAfrican National Roads Agency Ltd , 2004)

Figure 2: Braided steel wires implementedas road median. (ARMCO RSP, n.d., A)

Figure 3: W – shaped steel barrierimplemented as roadside barrier. (ARMCO

RSP, n.d., G)

An initial investigation of roadside barriers and the requirements needed to design for such asystem is undertaken. To ensure that the design of an alternative concept meets the need of theroad user and operator, requirements and specifications of a roadside barrier are developedfrom a systems engineering point of view.

2. IntroductionThe Committee of Land Transport Officials South Africa (COLTO 1999) defines roadsidebarriers as systems which are utilized to protect road users from man-made or natural hazards.The main function of roadside barriers is to redirect or contain errant vehicles from collidingwith other objects or entering hazards. Roadside barriers can be classified as rigid, semi-rigidor flexible systems, depending on the physical properties of the barrier and energy dissipationmethod. The (COLTO 1999) and other references refer multiple times to the AmericanAssociation of State Highway and Transport Officials’ Roadside Design Guides (AASHTO2011). These guides provide road agencies with vital information which can be used in thedevelopment of road standards and policies.

Roadside barriers need to conform to certain impact test specifications and vehicleperformance criteria that is defined by the South African National Standard number 51317-1of 2009 (SANS 51317-1 2009). The design specifications of roadside barriers should includethe on-road site conditions under which the barriers should be installed. A simulated realworld impact test is to be used to indicate the containment and performance levels of a barrieras classified in (SANS 51317-2 2009). It is imperative that a roadside barrier design conformsto the above mentioned SANS standards. Older standards such as the National CooperativeHighway Research Program (NCHRP 1993) also provide impact test standards and

performance measures and specifications for highway safety features such as roadsidebarriers.

The (Roads and Traffic Administration Branch 1984) and (COLTO 1999) define the warrantsand methods for installation of roadside barriers.

(Hawzheen et al. 2009) emphasize that lifecycle costs of a roadside barrier are just asimportant as the safety performance and investment costs, but are often neglected due toinsufficient knowledge and data of roadside barrier repairs and maintenance. (Stevens 2013)echoed the importance of including roadside barrier implementation and maintenancemethods during the design phase of a barrier, as these factors significantly influence thelifecycle costs. According to (Stevens 2013), the importance of implementing and maintaininga roadside barrier according to design specifications is also important, because the measure ofprotection provided by barriers significantly depend on these factors. (Stevens 2013) notedthat South African guidelines for maintenance and repairs do not exist. Roadside barriers areonly replaced when noticeable damage has been identified.

The installation, repair and maintenance of ARMCO barriers are provided by guides such asthe Federal Highway Administration’s (W-beam Guardrail Repair and Maintenance 1990)guide. This guide provides complete lists of equipment and tools, repair crew size and time,repair sequence guidelines and traffic control measures needed for these jobs.

(Douglas et al. 2009) evaluated how roadside barriers must be maintained and repaired, byinvestigating the current maintenance and repair policies of 40 United States and 8 Canadiantransportation agencies. (Douglas et al. 2009) further noted the high cost of maintaining andrepairing these barriers as well as the lack of maintenance guides as reasons for states andtraffic agencies not having sufficient policies in place.

(Stevens 2013 O) defines the different levels of ownership of road networks in South Africaand the parties responsible for each part of the network. Some of the challenges regarding themaintenance and implementation of the local road network are identified in this document.(Stevens 2013 O) explicitly states that funds are insufficient for a high standard ofmaintenance. It is often supplemented by means of synchronisation with job creationinitiatives. It is deduced that roadside barrier maintenance and new barrier installation areaffected by this shortage of funds. Hence a need exists for a low cost roadside barrier to bedeveloped.

An overview of the background and introductory study clearly points towards the need for aroadside barrier that is more cost effective to manufacture, maintain and repair over its entirelife cycle. In addition, local manufacturing industries would welcome new businessopportunities, creating synergy.

3. MethodologyThe following methodology or activities are anticipated to be executed during the project.

3.1 Use of Systems Approach The design of a new roadside barrier lends itselftowards the use of Systems Engineering as barrier design methodology, because it models aroadside barrier as part of a higher level road network system. A User Requirements Analysis(Halligan 2013), according to a Systems Engineering design approach, is to be used to

generate and validate the requirements of a roadside barrier. The solution space encompassinga feasible roadside barrier design can be described by using a User Requirements Analysis,with each stakeholder imposing different constraints on it.

Figure 4: Solution space of roadside barrier design to be described by User RequirementsAnalysis.

3.2 Description of High Level System The sub-system under considerationforms part of a passive safety system consisting of roadside furniture and road signs &markings, as described by (COLTO 1999). Road markings are signs, road surface letteringand graphics, lines, studs and traffic control devices. Roadside furniture include roadsidebarriers, fencing, bridges, fixed objects (e.g. “cat-eye” reflectors), service areas, kilometremarkers, escape ramps and lighting.

3.3 Roadside Barrier Sub-System The roadside barrier subsystem is proposed to bea barrier, fastened to wooden posts, that restrains and redirects out-of-control vehiclestravelling on a roadway. Secondary to the redirection and restraining functions, the roadsidebarrier defines the roadway limits and limits the movement of people and stray animals on tothe road (Roads and Traffic Administration Branch 1984).

The components of a system have certain attributes that contribute towards the functioning ofthe system. Examples of component attributes of a roadside barrier are the strength providedby the barrier material structure (quantitative attribute), the length or width of the barrier(configurative attribute), and corrosion protection of the barrier (characteristic attribute)(Blanchard et al. 2011).

In order to identify a system, it is classified according to its application and usage. A roadsidebarrier can be classified as a static system because it has physical structural components, butno operating, moving or flowing components. In contrast, a dynamic system has structural,operating and flowing components, such as the cooling system of an internal combustionengine. The processes of implementing and maintaining a roadside barrier is a dynamicprocess performed by a construction sub-system operating on a flow of construction materialsand labour. A static system usually forms part of a higher level dynamic system as a

subsystem or component. Therefore a roadside barrier is a component of a road network’spassive safety system, which is a dynamic sub-system (Blanchard et al.2011).

A system can only be effective and cost-effective when its life-cycle has been engineeredconcurrently with the system acquisition phase. Life-cycle engineering considers the design-,production- or manufacturing-, integration-, operation-, support- and maintenance-, phase-outand disposal tasks of a system. A life-cycle diagram of a system is shown in Figure 5,indicating the concurrent design or acquisition phases in series with the utilization phases.The numerous parallel tasks are subject to the two phases, as shown in Figure 5 (Blanchard etal.2011).

Life-cycle engineering is not considered within the scope of this study. The roadside barrier,which is a sub-system of a higher level passive safety system to the road network, has a highcapital and implementation cost and a short operating life span compared to its deployed and“ready” life. Thus it will be more important and beneficial to focus the engineering and designefforts on the operating phase of the roadside barrier.

Figure 5: Life Cycle of a System (Blanchard et al. 2011)

3.4 Roadside Barrier Sub-system Requirements The User Requirements Statement(URS) describes what is to be required of a roadside barrier. The following list indicates theinitial requirements as identified from the different stakeholder perspectives.

The roadside barrier must be produced from a suitable material which will provide the

necessary strength properties for a barrier.

The design must conform to the minimum performance specification as listed in the

SANS 51317-1 and 51317-2 standards.

The roadside barrier must be more cost effective for the operator than current roadside

barriers.

The roadside barrier must equal or be less than the current “ARMCO” barrier mass.

The roadside barrier must equal the current “ARMCO” barriers’ installation methods.

The roadside barrier must be able to be installed using basic hand tools (such as

spanners, wrenches, screwdrivers and vice grips).

The roadside barrier must be interchangeable with current “ARMCO” barriers e.g. if

an old barrier is removed from its posts, the new design must fit in its place.

The roadside barrier must require minimal maintenance.

The roadside barrier must carry the name or marking of its owner.

The roadside barrier must make provision for correct installation height and spacing

between barrier and post.

The roadside barrier must be able to be bent according to the curvature of any road

where installation of it is to be performed.

The roadside barrier must provide containment of or protection to stray animals and

pedestrians next to the roadway.

The roadside barrier must be resistive to corrosion.

The roadside barrier and relevant subsystems and components should be replaced after

being damaged by a vehicle colliding with it, and the induced damage warrants

replacement.

Safety Requirements for roadside barriers according to (COLTO 1999) are: (directly quoted)

The roadside barrier shall be able to have sufficient strength and stability to absorb the

impacting energy of an errant vehicle.

The roadside barrier shall redirect a vehicle parallel to traffic flow to prevent

secondary collisions.

The roadside barrier shall reduce the severity of injuries by reducing the impact forces

on occupants of the impacting vehicle.

During impact the roadside barrier shall suffer as little as possible damage and cause

as little as possible damage to the impacting vehicle.

The roadside barrier shall keep an impacting vehicle upright during and after impact.

The roadside barrier shall not cause any debris or fragments that could penetrate or

have a potential to penetrate the passenger compartment or cause danger to other

vehicles travelling on the roadway.

Roadside barrier requirements in terms of selection criteria, directly quoted from (COLTO1999), are:

Performance Capability: The selection criteria of a roadside barrier shall be

structurally able to – contain the design vehicle – redirect the design vehicle.

Deflection: The available room to deflect shall not be less than the expected roadside

barrier deflection.

Site Conditions: Influences of the slope approaching the roadside barrier and the

distance from the traffic lane shall influence the choice of barrier type.

Compatibility: The roadside barrier shall be compatible with adjacent systems (such as

bridge railings) and end treatments.

Cost: The full life cycle cost shall be considered in the economic evaluation of

alternative roadside barrier systems. A system with a relatively low installation cost

typically requires significantly more maintenance following impacts.

Routine Maintenance: Routine maintenance shall be described for the roadside barrier.

Collision Maintenance: Flexible and semi-flexible barrier systems require in general

significantly more maintenance than rigid systems.

Materials Storage Maintenance: Storage includes inventory items and storage space.

Simplicity Maintenance: Simpler designs are more likely to be installed correctly by

field personnel.

Field experience: Existing systems shall be monitored in terms of performance and

maintenance requirements to identify problems that can be reduced or eliminated by

the use of a different roadside barrier system.

4. Results and Discussion

4.1 Requirements AnalysisThe formulation of requirements aims to describe the problem or need of a customer.Although a customer understands his/her needs better than anyone else, and has absoluteownership of requirements, the customer’s description of the requirements can seldomexpress his/her needs completely or be regarded as absolutely valid. The customer’sdescription is not to be confused with the quality of completeness of a requirement. After asystem has been designed and developed, it is to be evaluated against the set of requirements.Therefore the need exists to analyse requirements to ensure that they are qualified and valid.According to (Halligan 2013) the relative cost to repair an error during the RequirementsAnalysis design phase is low compared to correcting an error during the Detailed Design,Integration or Validation Operation of a Systems Development Cycle. The diagram shown inFigure 6 indicates the methods in a Requirements Analysis, as well as the methods followedfor analysing the requirements of the roadside barrier in the encircled blue boxes.

Figure 6: Requirements Analysis Methodology. Adapted from (Halligan, 2013).

4.1.1 System Stakeholders The system stakeholders in the context of the roadsidebarrier are the owners or operators of the roadside barrier system. As described in theintroduction, the owners of the road networks and its relevant systems are the different levelsof district, provincial and national governments in a South African context. Subject to theoperators and owners of the roadside barrier system, the (road) users of the system are alsostakeholders. Road users are pedestrians and operators of vehicles. Not only do the users“use” the roadside barrier system, but also indirectly fund the system through various taxes.

4.1.2 Context Analysis The context analysis or context diagram, refer Figure 7,identifies each reference to an external system or particular element of the environment inwhich the system functions. A reference which provides inputs or receives outputs from thesystem is also identified (Halligan 2013).

RoadsideBarrierSystem

Vehicles Pedestrians

Stray Animals

Barrier Posts BarrierSpacers

Bolts andWashers

ReflectiveElements

Field/Maintenance

Personnel

ApproachingSlope

AdjacentBarriers

RoadCurvature

Figure 7: Roadside Barrier Context Diagram

4.1.3 States & Modes Analysis A state of an entity can be defined as itscondition, whereas the mode of an entity relates to its functioning, and can thus be defined asa function of it (Halligan 2013). The States & Modes analysis contributes to the clarificationof requirements specification and gaining clear and concise requirement statements withregards to the states & modes of an entity. The following list indicates the various states andmodes of the roadside barrier system. The relationship between the states and modes areindicated in Table 1.

Installed State: The roadside barrier is installed on posts, “ready” to perform

redirection and containment functions.

Damaged State: A roadside barrier is in a damaged state, after a vehicle has impacted

or collided with it. Thus it is not able to perform redirection and containment functions

any more. The roadside barrier is in need of replacement.

Disrepair State: The roadside barrier is in need of re-fitment or realignment to the

barrier posts, due to weather, environment or human influences on it.

Redirection Mode: The roadside barrier redirects a stray or off course vehicle back in

the direction of the road way on impact with the roadside barrier.

Containment Mode: The roadside barrier contains a vehicle from colliding with a

roadside hazard or lessening the impact of the collision with the roadside hazard on

the vehicle and occupants.

Table 1: Relationships between States and Modes of a Roadside Barrier system

Figure 8 indicates the States and Mode Transition Diagrams. These diagrams indicate thespecific transitions of states and modes that occur during the operation of the roadside barriersystem.

Figure 8: States & Modes Diagram

4.1.4 Parsing Parsing system requirements results in a new set of validatedrequirement statements, as shown in paragraph 4.1.5. This method clarifies the rationalreasoning of each requirement through parsing of a requirement. Phrases of each requirement,which deals with the Actor, Conditions for Action, Action, Object of Action, Constraints of

InstalledState

DamagedState

DisrepairState

RedirectionMode

ContainmentMode

Installed State M M X X

Damaged State M M P P

Disrepair State M M P P

DeployedMode

X P P X X

RedirectionMode

X P P X

ContainmentMode

X P P X

Legend X Is required to existsimultaneously with

Is required to be mutuallyexclusive

P Don’t care (permitted) Required

Action, Refinement or Source of Object and Refinement or Destination of Action, are definedand improved if necessary (Halligan 2013).

4.1.5 Final Requirements After performing the Requirements Analysis, the finalset of requirements are (additional to those specified in (COLTO 1999)):

The roadside barrier system must:

At least achieve the minimum stipulated performance specifications, as listed in SANS

51317-1 and -2, during impact or collision.

Cost less than current roadside barrier systems, per section of roadside barrier, in

terms of the capital expenditure.

Equal or be less than the current “ARMCO” barrier mass, per section of roadside

barrier.

Equal or improve upon the current installation methods in terms of standardized times

and Set Operating Procedures.

Be able to be installed with basic tools next to a road.

Be easily interchangeable with current “ARMCO” barriers.

Require minimal maintenance throughout its lifecycle.

Be identifiable and traceable to its owners.

Make provision for correct height and spacing installation.

Be able to follow road curvature on order.

Be resistant to corrosion.

Be able to be replaced in a short time after damage.

The resulting set of requirements, from the Requirements Analysis above, and PerformanceSpecifications, depicted in SANS 51317-1 and -2, converge to give measures of performanceagainst which possible system designs can be evaluated. Measures of Effectiveness (MOE’s)can further be compiled for the system and weighted. The system designs can further bemeasured against the weighted MOE’s in a Value Model. Results from both performancemeasurement methods can then be used to determine the best or most feasible system design.

5. ConclusionCurrent literature available on the design of roadside barriers is limited to the current barrierdesigns and implementation methods. This could be due to the relative age of these designs. Itcould further be considered worthwhile to review deflection displacement characteristics ofroadside barriers in terms of recent trends in automotive body design and passive safetysystems.

The Requirements Analysis resulted in a set of requirements which the roadside barriersystem has to conform to. Requirements and performance specifications from localgovernments can be investigated further. Systems Engineering processes such as the design of

the Logical Solution, Engineering Management, Lifecycle Design, Verification, Validationand Engineering Speciality Integration can all be used to design a roadside barrier system,from a Systems Engineering perspective, if such a system is deemed worthy of furtherinvestigation by the relevant stakeholders.

A roadside barrier can be an attractive new product venture for a local manufacturer, providedthat such a barrier conforms to the requirements and specifications for roadside barriersystems. Desirable further work includes the compilation of a cost-revenue model for thisbarrier system. It should be attractive for the local governments as well as the manufacturers.A barrier system is likely to succeed if the requirements of both local authorities andmanufacturers can be met.

6. AcknowledgementsAubrey Stevens, Cape Winelands Municipality, is acknowledged for technical and roadapplication information. Rick Allen and Charles De Villiers, Allens Meshco, is acknowledgedfor their manufacturing support. Ruan van der Merwe, University of Stellenbosch, isacknowledged for his assistance with the Stress Analysis.

7. ReferencesAASHTO, 2011. Road Design Manual. 4th ed. Washington, DC: American Association of StateHighway and Transportation Officials.

ARMCO RSP, n.d. Products - ARMCO Wire Rope Safety Fence. [Online]Available at:http://www.armcorsp.co.za/modules/text/manager.php?page=wire&Pid=16&Tid=2&W=[Accessed 05 August 2013].

ARMCO RSP, n.d. Products - Guardrail. [Online]Available at:http://www.armcorsp.co.za/modules/text/manager.php?page=guardrail&Pid=19&Tid=2&W=[Accessed 5 August 2013].

Blanchard, B. S. & Fabrycky, W. J., 2011. Systems Engineering and Analysis. 5th ed. Upper SaddleRiver(New Jersey): Pearson Education, Inc..

Committee of Land Transport Officials South Africa (COLTO), 1999. South African Road SafetyManual. Pretoria(Gauteng): Stanway Edwards Ngomane Associates.

Douglas, G. J. & Hampton, G. C., 2009. Evaluation of Current Repair Criteria for Longitudinal Barrierwith Crash Damage. Journal of Transportation Engineering, 1 April, 135(4), pp. 225-234.

Federal Highway Administration (FHwA), 1990. W-Beam guardrail repair and maintenance: A guidefor street and highway maintenance personnel, Washington, D.C.: s.n.

Halligan, R., 2013. Systems Engineering. Victoria: Project Performance International.

Hawzheen, K., Moudud, A. & Magnusson, R., 2011. Road Barrier Repair Costs and Influencing. Journalof Transportation Engineering, 1 May, 137(5), pp. 349-359.

National Cooperative Highway Research Program, 1993. NCHRP Report 350: RecommendedProcedures for the Safety Performance Evalutation of Highway Features , Washington, D.C.: NationalAcademy Press.

Roads and Traffic Administration Branch, 1984. Geometric Design Manual. 2nd ed. CapeTown(Province of Cape of Good Hope): s.n.

South African National Standards, 2009. SANS 51317-1:2009. 1st ed. Pretoria(Gauteng): SABSStandards Devision.

South African National Standards, 2009. SANS 51317-2:2009. 1st ed. Pretoria(Gauteng): SABSStandards Division.

Stevens, A., 2013. "Onderhoud en Bestuur van Landelike Provinsiale Paaie", Stellenbosch:Department of Infrastructure Development Services.

Stevens, A., 2013. Roadside Barriers in a South African Context [Interview] (15 May 2013).

The South African National Roads Agency Ltd , 2004. Annual Report, Pretoria: s.n.

8. BiographyAlbert van der Merwe is a final year Industrial Engineering student at the University ofStellenbosch. His interest in Systems Engineering and the synergy with design led to thisproject. He has completed several vacation work periods at Saab Grintek Defence, obtainingwork exposure of Systems Engineering in the context of military communication, softwareand Command & Control systems.

Nico Treurnicht lectures at the University of Stellenbosch.