The reasons for traffic congestion can be expressed in English as follows:
1. High population density
2. Inadequate road infrastructure
3. Poor traffic planning
4. Excessive vehicle ownership
5. Lack of public transportation options
6. Rush hour commuting
7. Illegal parking
8. Traffic accidents
9. Bad weather conditions
10. Construction work on roads
11. Insufficient public transportation frequency or capacity
12. Inefficient traffic signal management
13. Lack of traffic law enforcement
14. Urban sprawl
15. Special events or festivals attracting large crowds.