The most common and most likely answer to this crossword clue is the 4 plus 11 letter word DUAL CARRIAGEWAY
I've seen this crossword clue in Independent
D
U
A
L
C
A
R
R
I
A
G
E
W
A
Y
More clues leading to the result DUAL CARRIAGEWAY
Buddy explains!

The straight part
We know that "transport feature" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case transport feature = dual carriageway.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.