Looking up...
毎朝の通勤電車が混んでいて、座ることができない。
Every morning the commuter train is so crowded that I can't even get a seat.
For commuter trains to be crowded with passengers during rush hours.
通勤電車が混んでいる時間帯は、ストレスがたまる。
The time when commuter trains are crowded is stressful.
この路線は、ラッシュアワーになると通勤電車が混む。
This line gets crowded with commuter trains during rush hour.
Commonly used during morning or evening rush hours when trains are packed with salarymen and students.
Use this phrase when talking about the crowdedness of trains that people take to and from work or school, especially during peak hours. Avoid using it for trains that are crowded for other reasons (e.g., during holidays or events).
While '混む' literally means 'to be crowded,' in this context, it specifically refers to trains being packed with passengers during commuting hours. Don't use it for other crowded situations unless they are train-related.
This phrase is typically used in everyday conversation to describe the crowdedness of trains during peak commuting times. It is not used for non-commuter trains or outside of rush hours.