The Jam or The Police could be responsible for this and it annoys those in The Cars?
I believe the answer is:
roadblock
'the jam' is the definition.
(thesaurus)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for roadblock that I've seen before include "put in place by police after fugitive" , "Police barricade to halt traffic" , "Barrier constructed by police" , "Checkpoint" , "Barrier on way" .)