How are the separate brake systems for normal stopping and for parking and emergency braking in vehicles with air brakes controlled?
- Separately ✓
- In sequence, parking/emergency brake last
- Together
- In sequence, parking/emergency brake first
Answer: A. Separately
The brake system used for normal stopping and the spring brake system used for parking and emergency stopping are controlled separately.
Why this is the answer
The handbook describes two distinct systems working in different situations. Service brakes handle everyday stopping, and spring brakes are the separate system built for parking the vehicle or for an emergency when the service brakes fail, applying on their own once air pressure drops below the set level. Nothing in the text says one system is applied after the other during a stop, so the two are controlled separately rather than as a single combined or sequenced action.
Why the other answers are wrong
- B. In sequence, parking/emergency brake last — The parking and emergency spring brakes are not applied at the end of a normal stop; they are a separate system that stays off while the service brakes do the stopping.
- C. Together — They are not controlled together, because the handbook treats the service brakes and the spring brakes as two different systems for two different jobs.
- D. In sequence, parking/emergency brake first — The spring brakes do not come on first and then hand over to the service brakes; they engage for parking or when service brakes fail, not at the start of routine braking.
Remember it
Think of it as two jobs by two systems: service brakes stop you while driving, spring brakes hold you when parked or when the service brakes give out.