Many operators see the word 'PASS' on a Roller Brake Test printout and file it away. For the Traffic Commissioner, that 'PASS' is only the beginning of the story.
By Zed Aziz CMILT, Transport Consultant
In my years of consulting, I've seen one recurring mistake that puts O-Licences at risk more than almost any other: the "Pass/Fail" fallacy. Operators receive a Roller Brake Test (RBT) printout, see "PASS" at the bottom, and file it away. But if you aren't analysing the data behind that result, you might be driving toward a regulatory disaster.
A brake test isn't just a certificate of roadworthiness; it is a diagnostic tool for your maintenance culture.
On an MOT, an imbalance over 30% is a fail. However, if both wheels "lock" (stop turning) on the rollers, the machine automatically grants a pass. This is a trap.
Imagine Axle 2 on your trailer locks at 2,200kg on the nearside and 1,450kg on the offside. That is a 34% imbalance. The computer says "PASS", but in a real-world emergency stop, that trailer will pull violently to one side. Ignore this, and you are ignoring a mechanical defect.
To keep your fleet truly compliant, run this 4-step risk assessment for every printout:
| Symptom | Likely cause | Action |
|---|---|---|
| High imbalance (both systems) | Seized adjuster, oil on drum, or worn pads | Mechanical stripdown |
| High imbalance (service only) | Leaking air chamber or kinked hose | Pneumatic pressure test |
| High ovality (>5%) | Warped disc or "out of round" drum | Replace drum / disc |
Need a hand interpreting your brake test data? Our RBT Risk Assessment Generator and maintenance specialists can help — get in touch.
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