Query: All taxis in Delhi were ordered to switch to what type of fuel by March 1, 2016?
Context: Among the measures, the court ordered to stop registrations of diesel cars and sport utility vehicles with an engine capacity of 2,000 cc and over until March 31, 2016. The court also ordered all taxis in the Delhi region to switch to compressed natural gas by March 1, 2016. Transportation vehicles that are more than 10 years old were banned from entering the capital.