A traffic jam is when so many cars fill the road that nobody moves. Engines off, and a queue with no visible cause.
Many of them have no cause at all beyond one person braking, since a wave of braking travels backwards through traffic and can bring a motorway to a stop miles behind the original tap. That phantom jam is a genuinely studied phenomenon. British English also says a tailback, and congestion is the formal word. Being stuck in a jam is the standard excuse for lateness.
1phrasetraffic jamA long line of vehicles unable to move.
“They sat in a traffic jam for an hour and a half.”
Also accepted in games: jam, congestion
Practised in Travel & Transport, A Man Called Ove
First appears in chapter 4 of A Man Called Ove.
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