WIRE ROPE SAFETY FENCE
STANDARDS
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Introduction | |
Definition |
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Basic Criteria | |
Design Requirements |
BASIC CRITIERIA
Limitations on Use.
3.1 Wire rope safety fence shall not be used:
(a) where the length of fence at full height would be less than 24m.
(b) on horizontal curves of radius less than 300m where post spacing is 3.2m -
(angle of arc is < 60 degrees).
(c) on horizontal curves of radius less than 200m where post spacing is 2.5m.
(d) on horizontal curves of radius less than 50m where post spacing is 1.25m.
(e) on vertical sag curves of radius less than 3,000m.
(f) on central reserves having a width of less than:
(i) 3.14m when the support posts are
at 2.5m centres (see Figure 1).(ii) 2.75m when the support posts
are at 1.25m centres.(g) on central reserves for Emergency Crossing Points and Maintenance Crossing Points except where specific approval has been given by the appropriate authority.
(h) where the height of any kerb at the edge of the adjacent paved surface exceeds 110mm and the traffic face of the wire rope safety fence would be positioned less than 1.5m from the kerb face.
3.2 In addition, a wire rope safety fence shall not be connected to any other safety fence or bridge parapet. However, the wire rope safety fence can be interfaced with certain other types of safety fences when installed in accordance with the details shown on detailed interface drawings and specifically agreed with the appropriate road authority.
DESIGN REQUIREMENTS
General
4.1 The design of wire rope safety fence installations shall comply with the following layout and detailing requirements.
Layout
4.2 Layout requirements are as follows:
4.2a - Setback
(a1) set back at verge based on TD 32/93
The desirable minimum set-back shall normally be not less than 1.2m. It may be reduced to:
(i) 1.0m adjacent to an obstruction
(ii) 0.6m adjacent to any hardshoulder, hardstrip or road having a speed limit not exceeding 80 kph.
(a2) Set back at verge - RTA preferred practice
(i) The desirable minimum set back shall normally be not less than the road shoulder width + 0.1m, ie 0.6m from centre line of the post to the edge of the travelled way.
(a3) Set back at verge - VIC Roads recommendations
(i) For 2.5m post spacing desirable set back is 3.0m
(ii) For 2.5m post spacing minimum set back is 2.0m
(b1) Set back at central Reserve - based on TD 32/93
(i) Where there are no obstructions and there is only one safety fence between the carriageways and the support posts are at 2.5m centres, the minimum set-back shall be 1.5m.
(ii) In all situations other than (i) above (eg. two separate safety fences) the set-back shall normally be not less than 1.2m. It may be further reduced to an absolute minimum of 1.0m adjacent to short obstructions and on long structures provided the support posts are spaced at 1.25m centres.
(b2) Set back at central reserve - RTA preferred practice
(i) Set back is dependant on traffic speed and post spacing. For end anchor spacing greater than 100m the minimum set back distances are:
| Traffic Speed | Post Spacing | Minimum set back |
| 80 kph | 2.5m | 1.3m |
| 90 kph | 2.5m | 1.4m |
| 100 kph | 2.5m | 1.5m |
| 110 kph | 2.5m | 1.6m |
| 80 kph | 1.25m | 1.0m |
| 90 kph | 1.25m | 1.1m |
| 100 kph | 1.25m | 1.2m |
| 110 kph | 1.25m | 1.3m |
Note 1: 4 rope fences only permitted in Median
Note 2: 3 rope fences not allowed in median.
Note 3: Where anchor spacing < 100m some reductions in the set back can be made by halving post spacing. (only for 2.5m post spacing).
(b3) Set back in central reserve - VIC Roads recommendations
(i) Minimum set back for 2.5m post spacing is 2.0m.
4.2c - Clearance
(c1) Clearance (other than embankment) - based on TD32/93
(i) For both verge and central reserve, the minimum clearance shall normally be not less than:
(a) 1.5m when the support posts are at 2.5m and 3.2m centres.
(c) (b) 1.3m when the support posts are at 1.25m centres.
Note: 3 or 4 rope systems are allowed in verge situations.
(c2) Clearance (other than embankments) - RTA preferred practice
(i) Minimum clearance in verge/central reserve for anchor spacing greater than 100 metres.
| Traffic Speed | Post Spacing | Clearance - Verge |
Clearance - Central Reserve |
| 80 kph | 1.25m | 1.0m | 1.0m |
| 90 kph | 1.25m | 1.1m | 1.1m |
| 100 kph | 1.25m | 1.2m | 1.2m |
| 110 kph | 1.25m | 1.3m | 1.3m |
| 80 kph | 2.5m | 1.3m | 1.3m |
| 90 kph | 2.5m | 1.4m | 1.4m |
| 100 kph | 2.5m | 1.5m | 1.5m |
| 110 kph | 2.5m | 1.6m | 1.6m |
| 80 kph | 3.2m | 1.8m | N/A |
| 90 kph | 3.2m | 2.0m | N/A |
| 100 kph | 3.2m | 2.1m | N/A |
| 110 kph | 3.2m | 2.25m | N/A |
Note 1: 3 or 4 rope systems are allowed in verge situations.
(c3) Clearance (other than embankments) - VIC Roads Recommendations
(i) Minimum Clearance in Verge/Central Reserve Situation:
If 2.5 metre post spacing - Min. Clearance
2.00 metresIf 1.25 metre post spacing - Min.
Clearance 1.50 metres If 1.0 metre post spacing - Min. Clearance
1.30 metresNote: It is generally recommended in Road Note 3-18 (July 1995) that Flexible Barriers be restricted to the central reserve (median). If it is proposed for use on the Verge appropriate approval is required.
(d) Visibility
The layout of wire rope safety fences shall comply with the requirements of sight distance given in the relevant road authority standard. (State or Federal).
(e) Transverse Ground Profile
The ground beneath, and to each side of the fence and between any kerbing, shall be generally level and shall be free from obstructions within the set-back and clearance dimensions.
(f) Height of Fence
Where the horizontal distance from the traffic face of the fence to the edge of the adjacent paved surface is less than 1.5m, the heights of the ropes shall be measured from the level of the adjacent paved surface. Elsewhere the heights of the ropes shall be measured from the general ground level beneath the line of the safety fence. (see figure 1).
(g) Length of Fence
(i) Where a wire rope safety fence is provided in front of an obstruction which can only be impacted from one side, it shall be extended at full height not less than 30m in advance of the obstruction and shall continue at full height not less than 7.5m beyond the obstruction.
(ii) On embankments the length of wire rope safety fence should be as determined by the appropriate road authority.
Detailing
4.3 Detailing requirements are as follows:
(i) Foundations may be designed to resist the effects of a horizontal shear of 10.25 kN combined with a bending moment of 6.0 kNm in a plane at right angles to the fence.
(ii) The construction details for driven posts and concrete foundations shown on the LB Series of drawings shall be specified wherever appropriate. However, specially designed foundations will be required to conform to the loading requirements given in (i) above where the standard foundation design is not suitable due to poor ground conditions and/or where posts and foundations would interfere with cables, ducts or drainage systems.
(ii) Where a socket is cast into an in situ concrete foundation to facilitate post replacement, the foundation shall be of sufficient size to ensure that it is not displaced when the post is knocked down under vehicle impact.
(a) Anchors
Each rope length shall have two anchors at each end. Where intermediate anchors are required, they shall be located not less than 60m apart longitudinally.
(b) Ropes
The length of line rope between anchors shall be not more than 1385m. In addition in a four rope system two ropes, one upper and one lower, shall be terminated on each end anchor and where required on one end of an intermediate anchor. In the three rope system two ropes the upper and one lower, shall be terminated at the outer end anchors.
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