How do I confirm the fifth wheel is engaged?

Check the locking jaw is closed around the kingpin, the handle is in the locked position, and do a tug test — never rely on a visual glance alone.

What are susie lines?

The flexible air lines (typically red and yellow) that connect the tractor unit's braking system to the trailer. They must be connected, undamaged and not chafing.

Do landing legs need checking?

Yes — they must be fully wound up and secured before moving, or they can catch and cause damage or a hazard.

Walkaround check guide

How to check the coupling on a daily walkaround

Nothing on an artic matters more than the coupling. If the trailer isn't properly connected, everything else is academic.

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In short

The coupling check applies to articulated and drawbar combinations. It confirms the fifth wheel or drawbar is correctly engaged and locked, the air and electrical connections are secure, and the landing legs are fully raised before the combination moves.

What to check

Checking coupling, step by step

Fifth wheel or drawbar coupling correctly engaged and locked
Kingpin fully home and the locking jaw closed
Landing legs fully raised and secured
Susie (air) lines connected and not chafing or leaking
Electrical (ABS/lighting) connections secure
Trailer parking brake released only once coupled

Common defects

Incorrectly engaged fifth wheel

Chafed or leaking susie lines

Landing legs not fully raised

Loose electrical connections

When to fail it

Never move until the coupling is confirmed correctly engaged and locked. Fail the item for any coupling, connection or landing-leg fault — a dropped trailer is catastrophic.

Why it matters

A trailer that uncouples in motion is one of the most serious failures possible. The coupling check is a critical, non-negotiable part of the daily walkaround.

More guides

Other walkaround check items

Checking tyres Checking brakes Checking lights Checking mirrors & glass Checking steering Checking leaks & fluids Checking wipers & washers Checking load security Checking number plates

FAQ

Checking coupling, answered

Keep reading

Walkaround checksThe full DVSA daily walkaround check app for every vehicle.The complete guideWhat a DVSA walkaround check is and the duties behind it.Free check listThe full DVSA daily walkaround check list, free to download.

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