DO1 Driver/Operator Inspection — practice test
DO1 is the EVT Driver/Operator Inspection exam - the readiness test every apparatus driver is accountable to before the wheels roll. It is not a repair exam; it is a prove-it-is-safe-to-respond exam. Operators fail it by treating it like a casual walk-around instead of a standards-based inspection: they can start the truck but cannot state the low-air warning point, the governor cut-out range, or what actually puts an apparatus out of service.
Studying for DO1 (Driver/Operator Inspection)? Overhaul Prep has 86 verified DO1 questions written to the current task list — in the same formats the real exam uses (direct, Technician A/B, EXCEPT and most-likely-cause). Every answer comes with a written explanation, so you learn why instead of memorising a letter.
What's on the DO1 test
DO1 covers the daily and pre-trip inspection and operational readiness of fire apparatus: engine and fluid checks, the full air-brake inspection sequence (build-up, governor cut-in and cut-out, low-air warning, static and applied leakage, spring/parking brakes), tires and wheels, warning devices and emergency lighting, pump and water-tank readiness, operator-level aerial checks, equipment and hose-load securement, and the driver/operator's duty to document defects and remove an unsafe unit from service. Expect procedure, pass/fail criteria and judgment - not deep component repair.
High-yield DO1 topics
The material that shows up year after year. If you're short on time, start here.
- The low-air warning device must activate by about 60 psi, before the spring brakes apply.
- Governor cut-out is typically about 120-125 psi; cut-in is roughly 20-25 psi below that.
- A safety-related defect found on inspection means the apparatus is documented and removed from service - not driven.
- Know the pump-shift / 'OK to pump' indicator and the tank-to-pump valve before you need water.
- Tire tread depth and inflation, lug/rust streaks, and wheel damage are daily go/no-go items.
Where techs lose points on DO1
Good technicians miss these — not from lack of skill, but because the question is built to catch them.
- Confusing the low-air warning point (about 60 psi) with the spring-brake apply pressure (roughly 20-45 psi).
- Assuming an air dryer means the reservoirs never need draining - they still do.
- Treating a 'minor' brake or steering defect as report-it-later instead of out-of-service-now.
A study plan that works for DO1
Roughly two weeks of real preparation, in the order that actually builds on itself.
- Drill the air-brake sequence until you can recite it cold: build-up, governor cut-in/cut-out, static and applied leakage, low-air warning, spring-brake apply.
- Walk your own rig the way DO1 asks - narrate each check out loud and the number or condition that fails it.
- Work the pump and water-tank readiness checks and the operator-level aerial inspection.
- Finish on judgment: what gets documented, what puts a unit out of service, and safe-driving/backing responsibilities.
Sample DO1 questions
Straight from the bank — answers highlighted, with the explanation underneath.
On a properly functioning air-brake system, at what approximate pressure does the governor cut OUT and stop the compressor from loading more air into the tanks?
- About 60 psi
- About 90 psi
- About 125 psi
- About 150 psi
After the governor cuts out and the driver makes several brake applications, the compressor should begin loading the tanks again (cut in) at approximately:
- 100 psi
- 60 psi
- 40 psi
- 20 psi
In a dual air-brake system, published standards say air pressure should build from 85 to 100 psi within about:
- 45 seconds
- 3 minutes
- 10 seconds
- 5 minutes
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