You are assembling a set of two trailers with substantially different loaded weights. Which order does the manual recommend for the safest handling?
Correct answer: The more heavily loaded trailer first, immediately behind the tractor.
For the safest handling, place the heavier semitrailer ahead of the lighter one. Multiple-trailer combinations require attention to how the load is distributed between units.
Source: Idaho CDL Manual, July 2026 edition, 2022 CDL Testing System / July 2022 body, 7.2.1 Coupling Twin Trailers (printed 7-1); physical PDF page 96. ↗
You are choosing a rest-area parking space for a set of doubles. Which feature deserves special consideration?
Correct answer: A route that lets the entire rig pull straight through when leaving.
The manual stresses avoiding a parking position that traps doubles or triples in a difficult escape. Plan the exit before entering the space.
Source: Idaho CDL Manual, July 2026 edition, 2022 CDL Testing System / July 2022 body, 7.1.7 Parking the Vehicle (printed 7-1); physical PDF page 96. ↗
A set of doubles is ready for travel. How should the service and supply shut-off valves at the rear of each trailer be positioned?
Correct answer: Open at the first trailer and closed at the rearmost trailer.
Air must flow through intermediate connections to the rear unit, while the final exposed outlets must be closed. Check dolly valves as applicable too.
Source: Idaho CDL Manual, July 2026 edition, 2022 CDL Testing System / July 2022 body, 7.3.1 Additional Checks - Double and Triple Trailers (printed 7-3); physical PDF page 98. ↗
During a properly secured air-continuity check, no air escapes when you briefly open the final trailer’s service-line valve with the service control applied. What should you do?
Correct answer: Find and correct the lack of air flow through the trailers and dollies before travel.
The check establishes that air reaches the rear of the complete combination. A closed intermediate valve or other problem can leave rear brakes without the required control pressure.
Source: Idaho CDL Manual, July 2026 edition, 2022 CDL Testing System / July 2022 body, 7.4.1 Additional Air Brake Checks (printed 7-4); physical PDF page 99. ↗
The converter dolly’s eye is resting in the front trailer’s pintle hook. What additional connection checks are still necessary?
Correct answer: Check that the hook is latched and the safety chains are secured.
A seated eye is not the complete connection check. Inspect the latch, chains, air connections, and electrical connections before operation.
Source: Idaho CDL Manual, July 2026 edition, 2022 CDL Testing System / July 2022 body, 7.3.1 Additional Checks - Converter Dolly (printed 7-4); physical PDF page 99. ↗
A helper reaches for the pintle-hook latch while the dolly is still supporting the rear trailer. What is the concern?
Correct answer: The dolly tow bar can fly upward; remove the dolly from beneath the rear trailer before unhitching it.
The manual warns not to unlock the pintle with the dolly still under the rear trailer. Follow the safe uncoupling order and secure every unit.
Source: Idaho CDL Manual, July 2026 edition, 2022 CDL Testing System / July 2022 body, 7.2.2 Uncouple Converter Dolly (printed 7-3); physical PDF page 98. ↗
