When you’re installing signage on a 100km/h road, you’re not just putting a post in the ground. You’re placing infrastructure into a high-speed, high-risk environment, and that includes the support structure beneath the sign itself.
Frangible sign structures are designed specifically for these conditions. At Tranex, we work alongside contractors, councils and state government departments delivering signage into regional highways and state-managed corridors, where the safety conditions are different. Traffic moves faster, heavy vehicles are common, and the consequences of roadside impact are more severe.
Frangible supports may not look any different to drivers, but they play an important role in how roadside infrastructure behaves if a collision occurs.
In this blog, we’ll explore why frangible sign posts are critical on high-speed roads and where they’re most commonly used.
What Are Frangible Sign Structures?
A frangible sign structure is designed to break away in a controlled manner if struck by a vehicle.
Instead of behaving like a rigid obstacle, the support system is engineered to reduce the force transferred during impact. It’s part of a broader road safety approach, one that considers not just visibility and compliance, but what happens in a worst-case scenario.
The goal isn’t to eliminate risk but rather reduce impact severity where possible. On high-speed roads, that matters.
Why Frangible Sign Supports Are Critical on 100km/h Roads
Speed changes everything. At 100km/h, the impact involved in a collision is significantly greater and drivers have less time to correct mistakes. On state highways and regional freight corridors, vehicles move quickly and often over long distances. Heavy transport is part of daily traffic flow, and factors like wildlife or fatigue are real considerations.
In these environments, roadside infrastructure plays a critical role in overall safety outcomes. If a vehicle leaves the carriageway at 100km/h, rigid posts can increase injury severity and damage to the vehicle. Frangible systems are designed to respond differently to reduce overall impact.
MASH-Approved Frangible Sign Structures: What It Means
MASH stands for Manual for Assessing Safety Hardware. It’s the recognised testing standard used to assess how roadside safety hardware performs during vehicle impact.
In practical terms, MASH testing evaluates how a structure behaves when struck at speed, including vehicle stability and occupant risk.
For frangible sign structures, MASH approval provides confidence that the system has been independently tested under high-speed conditions. That’s why it’s commonly required, or strongly expected on:
- State road projects
- Major transport corridors
- 100km/h regional highways
- Government infrastructure programs
Where Frangible Sign Structures Are Typically Used
You’ll most often see frangible supports used for:
- Large directional guide signs
- Advance warning signage
- Permanent wayfinding on high-speed roads
- Long-term roadside infrastructure
Think of a regional highway connecting growing communities. Or a freight route carrying B-doubles day and night. Or a major arterial undergoing safety upgrades. In these environments, signage needs to do more than stand upright. It needs to be designed with impact safety in mind.
Built for Real Road Conditions
High-speed corridors aren’t forgiving. They face open wind exposure, coastal air and salt corrosion, long maintenance intervals, and continuous vibration from heavy traffic.
Frangible sign structures are designed to operate in these environments while still performing safely in an impact scenario.
That balance is important.
Frangible signals are strong enough to endure the elements and engineered to respond differently when struck.
Supporting Safer Outcomes on State Roads
Road safety strategy has evolved. Of course, the ultimate goal is always to prevent crashes, but we also want to reduce harm when crashes do occur.
Frangible sign supports sit within that broader passive safety framework. They don’t change how a sign looks. They don’t change the message drivers read. But they do change how the roadside infrastructure behaves if something goes wrong.
On 100km/h roads, that’s not a small detail. It’s part of responsible infrastructure planning.
If you’re reviewing roadside infrastructure on high-speed corridors or planning future upgrades, the Tranex team can support you with compliant frangible sign support solutions aligned to state road requirements. Contact us today.
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