The CNG bus fleet of Delhi Transport Corporation has aged considerably, with all 3,191 CNG-run buses now over 10 years old. This has increased the vulnerability of the fleet to breakdowns. While CNG buses in Delhi are allowed to run for 15 years, experts recommend retiring them after 10 years due to extensive usage and rough condition. The number of CNG buses in Delhi has decreased over the years, but there has been an addition of 1,300 electric buses. The lack of new bus procurement is attributed to issues with the annual maintenance contract and vendor concerns. This has resulted in frequent breakdowns, causing congestion and slowing traffic movement. Former head of transport planning, PK Sarkar, suggests that the fleet of buses should be at least 15,000-strong, and buses should be replaced every 8 years. Delhi government plans to increase the fleet to 10,480 buses by 2025, with 80% of the fleet being electric, in order to reduce carbon dioxide emissions.