The popular three-wheeled vehicles known as auto rickshaws are common in Asian cities where due to their older two stroke engines they have been significant contributors to the current air quality issues that plague the urban areas. Recent changes to four-stroke engines as well as those powered by diesel, compressed natural gas (CNG) or liquefied petroleum gas (LPG) reduce the pollution and greenhouse gas emissions. However, because of the large number of vehicles emission of such vehicles is still an important issue.