Barrier System Standards in Alberta
The province of Alberta has well-defined requirements for barrier systems for both roadside barriers and median barriers. Alberta uses the recommendations of the National Cooperative Highway Research Program (NCHRP) to establish these requirements, and all barrier systems used in the province must meet specific ratings established by NCHRP in their Report 350. Below are the system types approved for roadside use in Alberta with some information about their specs:
Roadside Barriers:
• Alberta Weak Post W-Beam: This beam is made of plastic or wood. It’s defined as “flexible” in terms of resistance to force. Its minimum system length is 22.86m for areas with speed limits under 70 km/hr and 45.72m for areas with speed limits over 80 km/hr.
• High Tension Cable: This type of roadside barrier is made of steel. Its resistance to force is rated as “flexible.” And it meets TL-3 or TL-4 NCHRP guidelines.
• Cast-in-Place Barrier: Made of durable concrete, Alberta authorities classify this barrier as “rigid.” The cast-in-place barrier must meet either TL-4 or TL-5 standards established by the NCHRP. Cast-in-place barrier should have a minimum system length of 30m.
• Modified Thrie Beam: This is a semi-rigid steel post with a minimum system length of 50m. It meets TL-4 requirements.
• F-Shape Precast Concrete Barrier: According to crash tests, this concrete barrier wall should offer semi-rigid strength. It should also meet TL-3 requirements and have a minimum system length of 45m. Note: New Jersey style precast concrete barrier may be used if replacing or repairing a section of existing barrier that is in the New Jersey style barrier. This would be the case if New Jersey style barrier was installed for a road project before Alberta updated their standards to require use of F-shape barrier. New Jersey barrier wall and F-shape barrier wall must never be combined.
• Standard Thrie Beam: A semi-rigid, steel post type barrier, this differs from the modified thrie beam in that it must meet TL-3, rather than TL-4 requirements. Its minimum system length is 50m.
• Strong Post W‐Beam: Made of either plastic, wood, or steel, it must be semi-rigid in strength and have a minimum system length of 50m.
• Weak Post Box Beam: This is a steel post system with semi-rigid strength. It must be TL-3 approved, and its minimum system length is 100m.
Note: Whether a barrier system is considered, flexible, rigid, or semi-rigid is based on design deflection, or the distance the system moves upon impact, measured at the face. In general, flexible systems move 3.5m upon impact. Rigid systems move 0m (or minimally if at all). And semi-rigid systems move 1.5m or less.
The requirements for median barriers in Alberta differ slightly from the requirements for roadside barriers, particularly in terms of required NCHRP ratings. This is because roadside barriers are engineered to be impacted on one side only, while median barriers must be able to withstand force from both sides. Here are the approved types of median barriers in the province with their necessary NCHRP ratings:
• Cast‐In‐Place F‐Shape Concrete Barrier: TL-4 or TL-5
• Cast‐In‐Place Single Slope Concrete Barrier: TL-4 or TL-5
• High Tension Cable Barrier Systems: TL‐3 or TL‐4
• Modified Thrie Beam: TL-4
• Precast F‐Shape or Single Slope Concrete Barrier: TL-3
• Strong Post W-Beam (wood, steel, or plastic posts): TL-3
• Weak Post Box Beam: TL-3
It’s important to be aware that all F-shape, pre-cast concrete barrier used in median areas must be rigid and have minimal design deflection. This notably differs from the semi-rigid requirement for F-shape barrier if used roadside. Additionally, both roadside and median pre-cast concrete barrier in Alberta needs to use crash tested joints between units. In either instance, use of joints between units allows for greater strength and less movement upon impact.
To learn more about barrier wall, visit our blog titled "Barrier Wall Styles and Uses".
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