2 km road or 2-km-long road?

Veron   Fri Mar 28, 2008 6:57 pm GMT
In case I take "a 2-year-old child" as an example, and apply it as a pattern when making an adjective phrase of the structure "a road which is 2 kms long", I would expect "a 2-km-LONG road". However, I often come across "a 2 km road" (without "long"). And the case is the same with kg and other units. Is it correct? And if it's correct, can anyone explain me the logic behind it?
Estel   Sun Mar 30, 2008 3:51 pm GMT
I personally have never said "a 2-km-long road." Not that I used kilometer in my daily speech anyway. But even with miles, I'd still say "a 2 mile road."

I think the reason behind this is that we already know that we're talking about the road's length to begin with. so we just left "long" out of the expression.

Let's wait and see what others say.