The most common and most likely answer to this crossword clue is the 9 letter word TAILBACKS
I've seen this crossword clue in The Times
T
A
I
L
B
A
C
K
S
Buddy explains!
The straight part
We know that "traffic queues" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case traffic queues = tailbacks.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does TAILBACKS mean?
TAILBACKS noun- A line of motor vehicles causing or the result of traffic congestion or a traffic jam; backup.
- A running back or halfback who lines up furthest to the rear in an I formation.