Bridge Approaches

Rigid barriers constructed from concrete or heavy-duty steel sections are predominately used on bridges where there is no available space to accommodate barrier deflection.

In many instances, the areas on either side of a bridge are shielded with a longitudinal barrier such as a W-beam guardrail.

The connection between a guardrail and a concrete barrier is also known as a ‘transition’ or ‘bridge approach’ system.

The key function of a bridge approach system is to reduce the potential for vehicle pocketing, by way of providing a continuity of protection when two different guardrail systems are connected.

thrie beam bridge approaches
hot dip galvanised bridge approaches
thrie beam bridge transition

How do bridge approaches work?

Connecting a semi-rigid guardrail barrier to a rigid barrier installed on a bridge provides barrier continuity.

The transition area gradually increases the lateral stiffness of the semi-rigid guardrail barrier, to reduce the potential for vehicle pocketing at the connection with the rigid concrete barrier.

A transition area will provide a gradual increase in stiffness through techniques such as reducing the spacing between supporting posts, double layering the standard W-beam rail elements (also known as ‘nesting’) and triple corrugation (by way of providing a transition from W-beam rail to a thrie-beam rail).

Features and Benefits

  • Sturdy, durable materials (such as concrete and steel) are used to provide continuity of protection between the two barrier systems.
  • Reduced spacing between supporting posts reinforces the rigidity between the guardrail barrier and the concrete barrier, strengthening the supportive structure.
  • Bridge approaches can be used alongside W-beam and thrie beam guardrail systems, offering triple corrugation to enhance bridge safety.
  • The gradual increase in stiffness from a semi-rigid barrier to a rigid barrier serves to promote the containment of the bridge approach structure, effectively reducing the potential for vehicle pocketing at the abutment of the rigid barrier.

As industry experts, Safe Direction are aware that transition designs should comply with road authority specifications and abide by the requirements of each Australian state. All our bridge approach products are manufactured in accordance with state and road agency specifications and adhere to AS/NZS 4680 industry requirements regarding hot dip galvanised components.

To find out more about our bridge approaches, get in touch with Safe Direction on 1300 063 220.