The term "traffic jam" is generally considered countable because you can have one traffic jam, two traffic jams, and so on. Each occurrence of a traffic jam can be counted individually. However, when referring to traffic congestion in general, it might be used in an uncountable sense, but this is less common.
Transport is both countable and uncountable as a noun.
countable
uncountable
Uncountable
uncountable
The gerund painting is a countable noun, as in "There are 12 paintings in this room."
few is countable
countable
Countable
The noun 'steel' is an uncountable (mass) noun, a word for a substance.
he asked me if the word fire wood countable or uncountable?
Yes, the noun 'traffic' is an uncountable noun, an aggregate noun, a word representing an indefinite number of elements or parts.