Week 7#
Fencing, signage and wildlife crossings#
The Best Result In The Literature Is Also The Hardest One To Fund#
Four mechanisms#
- exclude — fencing
- redirect — a safer crossing (underpass, culvert)
- change driver behaviour — signage, dynamic warnings
- change road-use conditions — sightlines, lighting, speed
Most measures you’ll compare today combine 1 and 2.
Fencing works until it doesn’t#
A fence that ends doesn’t remove animals from the area — it relocates where they cross: to the end of the fence.
This is a real displacement effect, and a source of measurement noise in the studies you’re about to read.
Usage ≠ collisions#
A well-used underpass is evidence the structure works as a crossing.
It is not, on its own, evidence that road collisions went down.
Two different measurements. Don’t recommend on the wrong one.
What the evidence says#
Rytwinski et al. (2016), PLoS ONE — a meta-analysis, not a single study.
Comparing candidates#
| Measure | Evidence | Maintenance | Approval |
|---|---|---|---|
| Fencing + crossing | Strong | High | High |
| Crossing alone | Evidence-limited | Moderate | Moderate |
| Static signage | Weak | Low | Low |
| Dynamic warning | Untested here | Moderate | Moderate |
| Reflectors | Weak | Low | Low |
Evidence strength and approval complexity run in opposite directions.
Illustrative costs — fictional teaching figures#
| Measure | Upfront (AUD/km) | Annual maintenance |
|---|---|---|
| Fencing + crossing | $180,000 | $6,000 |
| Crossing alone | $140,000 | $4,000 |
| Static signage | $2,000 | $200 |
| Dynamic warning | $25,000 | $3,000 |
| Reflectors | $4,000 | $500 |
Rounded, illustrative, not a real quote.
Why “install everything” isn’t a recommendation#
- competes for the same limited budget
- competes for the same finite approval bandwidth
- a list of every measure is a refusal to choose
One primary measure, argued for one site. That’s the shape Week 12 will ask for again, at the scale of the whole proposal.
Three sites today#
Bunjalung Ridge Road — 15 km, low traffic, small council budget.
Coorabin Road — 38 km, moderate traffic, two known clusters.
Merricourt Highway — 51 km, high traffic, slow state approval pipeline.
Same evidence table. Different answer at each site.
Next week#
Whatever gets recommended, someone has to approve paying for it — and if a hazard was known and nothing was done, someone has to answer for that too.
Week 8 starts exactly where a sign, a fence, or the absence of either, turns into a question of who is liable.