Road safety barrier systems are engineered barriers designed to protect drivers and pedestrians from being injured in the event of an accident. These systems are installed along roadsides and outline a barrier that ensures drivers stay on the correct side of the road. They also help define lanes, create traffic calming areas and reduce the risk of head-on collisions. The barrier system is available in a number of different materials and sizes and can be used in both urban and rural settings. The finish available is usually cement or polyurethane, and a range of colours are available to suit any project. We manufacture and supply highway road safety barrier meeting New Zealand Standard and international quality requirements set by other countries.
Our road safety barrier system comprises generally following one or a combination of the following components:
•Roadside and Median Barriers,
•Bridge Barriers,
•Crash Cushions and End Terminals,
•Barrier Transitions.
SELECTION OF ROAD SAFETY BARRIER SYSTEMS
Minimum Performance Standard
The minimum performance level for a state highway road safety barrier system is NCHRP 350 Test Level 3 (TL-3). However, in many circumstances, barriers complying with higher test levels will be necessary because factors such as traffic conditions, traffic volume and composition and the cost effectiveness of various safety alternatives must all be considered in the design of road safety barrier systems.
Designers should determine the performance level required for a roadside/median barrier on a case by case basis after due consideration of all factors involved. For example:
(a) The standard roadside protection is a TL-3 barrier but some features, such as a school playground located close to the toe of fill embankment on the outside of a high speed horizontal curve, warrant the provision of a higher performance roadside barrier.
(b) High proportions of heavy and/or dangerous goods vehicles in the traffic stream will usually require TL-4 barriers as a minimum.
(c) Even higher performance barriers, ie. a TL-5 barrier that will contain 36,000 kg truck or a TL-6 barrier that will contain a 36,000 kg tanker, should be used at locations where there are high proportions of heavy
and/or dangerous goods vehicles in the traffic stream, and there would be serious consequences if such a vehicle penetrated, or rolled over, the barrier.
(d) The standard bridge edge protection is a TL-3 barrier but the Transit New Zealand Bridge Manual (Bridge Manual) edge protection criteria will often require the provision of a TL 4 barrier, which will contain an 8,000 kg truck, in most cases.
The Bridge Manual contains a method for determining the appropriate barrier test level for any given situation and it must be complied with when dealing with barriers on bridges. The method is also equally relevant for determining the appropriate test level for roadside and median barriers.
APPROVED ROAD SAFETY BARRIER SYSTEMS
Only those road safety barrier systems listed in NZTA M23: Appendix A are approved for use on state highway roads.
Other products that have met NCHRP 350 requirements, may be approved for use on state highways, on application to the New Zealand Transport Agency Traffic and Safety Manager.
Road safety barrier systems used on bridges must conform to the requirements of Transit New Zealand’s Bridge Manual.
The approval of NZTA Traffic and Safety Manager is required for a road safety barrier system to be listed in NZTA M23 Appendix A.The primary criterion for the approval of a barrier system is that it must have been successfully crash tested and the results evaluated in accordance with the National Cooperative Highway Research Program Report 350:Recommended Procedures for the Safety Performance of Highway
Features(NCHRP Report 350).In addition, consideration will also be given to the following:
•In-service Performance: In the case of a product with no demonstrable in service history an in-service trial is required, at the manufacturer/supplier’s cost or otherwise agreed with NZTA.
•Availability of SparesThe manufacturer/supplier will need tofor Maintenance:demonstrate that spare parts are available within an agreed timeframe.
If a road safety barrier system has not been crash tested in accordance with NCHRP Report 350, and its use on state highways is likely to be cost effective, then an alternative crash test regime will be considered, providing:
•the testing has been undertaken by a reputable crash test organisation, and
•the results certified as complying with an equivalent NCHRP Report 350 test level.
The minimum performance level for road safety barrier systems installed on New Zealand state highways is NCHRP Report 350 Test Level 3 (TL 3). The performance level of the road safety barrier systems approved for use on state highway roads is given in NZTA M23: Appendix A.
The minimum performance level required for road safety barriers on state highway bridges shall be determined by the method given in Appendix B, Section B3 of Transit New Zealand’s Bridge Manual.
The future maintenance costs of alternate systems should be considered in the barrier selection process. Normally, the initial cost of a system increases as its strength increases, but maintenance costs decrease. Conversely, a system having a relatively low installation cost usually requires significantly more maintenance following impacts. Maintenance factors can be grouped into three categories:
Routine maintenance costs are similar for all operational roadside barrier systems. Some cleaning and painting is occasionally done, but the use of preservative-treated wood posts and galvanized steel components has nearly eliminated the need for this work. Periodic re-tensioning of cable barrier systems may be required. Graffiti on concrete barriers can present an ongoing maintenance cost. Some systems may interfere more with roadside mowing and vegetation control.
The amount and cost of repairs after an impact by a vehicle can play an important role in the system selection. The number of impacts that are likely to occur along a particular section of barrier depends on a number of factors, primarily traffic speed and volume, road alignment and the distance between the edge of the traffic lane and the face of the barrier. The extent of barrier damage for any specific impact depends upon the strength of the system.
Collision maintenance costs may become an overriding consideration in areas where traffic volumes are extremely high, and barrier impacts are frequent, such as on urban expressways and motorways where barrier repair is difficult to accomplish without interfering with road users. For this reason, rigid concrete barriers (e.g. “F-type” profile), are often preferred at such locations, particularly in median applications.
A further consideration in collision maintenance for post and rail systems is the ability of the rail element and possibly the posts to be re-used after a hit. Savings may be possible if the rail can be straightened. In some cases, of course, the rail will be damaged beyond repair, in which case the salvage/scrap value may be a consideration.
Before selecting a barrier system, the future availability of the repair materials and their storage requirements should be considered. The need for stocking spare parts increases as the number of parts required increases. Thus, there are obvious advantages of using only a few barrier systems whose component parts are standardized, easy to stockpile and readily available.
The design of all road safety barrier systems shall be compliant with the crash tested design or the barrier system configuration given approval under Section 3: Approval of Road Safety Barrier Systems.Changes to the crash tested/approved design/configuration will deem the barrier system noncompliant with this specification.
The layout of all road safety barrier systems should comply with the relevant guidelines:
(a)Roadside Safety Barriers
The layout of all roadside barriers shall be in accordance with the requirements of Section 7.3 of the SHGDM:Longitudinal Road Safety Barriers.
(b)Median Safety Barriers
The layout of all median barriers shall be in accordance with the requirements of Section 7.3.12 of the SHGDM:Median Barriers.
(c)Bridge Barriers
The layout of all bridge barriers, i.e. the barriers physically on the bridge deck, shall be in accordance with the requirements of the Bridge Manual.
Barriers on the approaches to bridges shall be in accordance with Section 7.3 of the SHGDM: Longitudinal Road Safety Barriers.
All road safety barrier systems must be installed in accordance with the manufacturer’s instructions.
New Zealand Transport Agency |
State Highway Geometric Design Manual (SHGDM) Bridge Manual |
Joint Australian/New Zealand Standard |
AS/NZS 3845: 1999 - Road Safety Barrier Systems |
National Cooperative Highway Research Program (NCHRP) |
NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features |
American Association of State Highway and Transportation Officials (AASHTO) |
Roadside Design Guide (AASHTO RDG) The recommended comprehensive reference for the design and installation of road safety barrier systems on New Zealand state highways. |
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