SGI Class 1 License 4 — Questions and Answers
Question 1: What is the purpose of the tractor protection valve on a Class 1 vehicle's air brake system?
- It prevents the trailer brakes from over-heating
- It protects the tractor air supply if the trailer develops a major air leak (Correct answer)
- It equalizes air pressure between the drive axles
- It controls the application of spring parking brakes
Correct answer: It protects the tractor air supply if the trailer develops a major air leak
The tractor protection valve automatically closes to seal the tractor air supply if a major air leak occurs in the trailer, preserving tractor braking capability.
Question 2: Under SGI regulations, what is the minimum tread depth required for front steering axle tires on a commercial vehicle?
- 2 mm
- 3 mm
- 4 mm (Correct answer)
- 6 mm
Correct answer: 4 mm
Front steering axle tires must have a minimum tread depth of 4 mm to ensure adequate steering control and stopping ability.
Question 3: A Class 1 driver must complete a pre-trip inspection before driving. At minimum, how often must a post-trip inspection report be completed?
- Once per week
- After every trip or at the end of each day's work (Correct answer)
- Only when a defect is found during the trip
- Every 48 hours
Correct answer: After every trip or at the end of each day's work
NSC Standard 13 requires drivers to complete a Driver Vehicle Inspection Report (DVIR) at the end of every trip or workday.
Question 4: When approaching a railway crossing with a Class 1 combination vehicle, what is the maximum speed you may cross at if no train is visible?
- 30 km/h (Correct answer)
- 15 km/h
- 50 km/h
- Whatever speed is safe and prudent
Correct answer: 30 km/h
Commercial vehicles must slow to a maximum of 30 km/h when crossing railway tracks to maintain control over the crossing surface.
Question 5: What is the main reason a Class 1 driver should 'stab brake' rather than lock the brakes on a non-ABS equipped vehicle during an emergency stop?
- Stab braking builds up air pressure faster
- Locking brakes causes the trailer to push the tractor sideways (Correct answer)
- Stab braking activates ABS on all axles
- Locked brakes cause the engine to stall
Correct answer: Locking brakes causes the trailer to push the tractor sideways
Locking the brakes on a combination vehicle can cause the trailer to push the tractor in a jackknife; stab braking maintains steering control.
Question 6: In Saskatchewan, what is the consequence for a commercial driver found with a blood alcohol concentration (BAC) of 0.04 or above while on duty?
- A warning is issued for a first offence
- An immediate 3-day licence suspension under the Warning Range (Correct answer)
- The driver may continue if BAC is under 0.08
- No action is taken until BAC exceeds 0.08
Correct answer: An immediate 3-day licence suspension under the Warning Range
Commercial drivers with a BAC of 0.04–0.079 fall in Saskatchewan's Warning Range and face an immediate 3-day licence suspension.
Question 7: What does the yellow kingpin locking indicator on a fifth wheel tell the driver during a coupling inspection?
- The fifth wheel is properly locked and the kingpin is secured
- The fifth wheel locking jaw is open and the trailer is NOT secured (Correct answer)
- The air lines are connected correctly to the trailer
- The trailer brake system is pressurized
Correct answer: The fifth wheel locking jaw is open and the trailer is NOT secured
A visible yellow indicator (or open jaw indicator) means the fifth wheel lock did NOT engage around the kingpin — the trailer is not safely coupled.
SGI Class 1 License 4
What is the purpose of the tractor protection valve on a Class 1 vehicle's air brake system?