Evaluation of Odd–Even Day Traffic Restriction Experiments in Delhi, India

During periods from January 1 to January 15 and April 15 to April 30, 2016, the Government of the National Capital Territory of Delhi, India, implemented an odd–even vehicle rule. Under this rule, between 08:00 and 20:00, only cars with even-numbered plates were allowed to operate on even-numbered dates of the calendar and only cars with odd-numbered plates on odd-numbered dates. In light of the varying experiences of vehicle restriction practices from around the world, this study evaluated the effects of both phases of the odd–even policy on transport patterns and vehicle use in Delhi. Observational surveys were carried out at four locations in Delhi to observe traffic flow and vehicle occupancy data. Speed data were extracted for 38 origin–destination pairs during the January phase and for 66 pairs for the April phase, with a sample of roads from all over Delhi and with Google Maps API (application programming interface) software. During the experimental periods, car flow rates on roads were reduced by less than 20%, but rates increased for motorized two-wheelers, buses, and autorickshaws. There was an insignificant rise in car occupancy rates: most car owners did not opt for carsharing. No improvements in levels of particulate matter with aerodynamic diameter < 2.5 µm (PM2.5) were detected. These experiments show that the odd–even rule was not effective in reducing measureable PM2.5 pollution in Delhi.