India has the second largest road network in the world. The new highway numbering system was introduced in April 2010. National Highway Authority of India (NHAI) was established in 1988 and is responsible for development, management, and maintenance of national highways (NH) in India.
Prior to the current system, the NH was numbered arbitrarily, and gave no sense of location or direction to the motorists. It has been over 10 years since the change was introduced, though very few motorists can claim to have command over the process and pattern of numbering a NH. The new numbers are based on the geographic location and direction of the NH.
How to Read the 3-digit NH Numbering System
NH 8: Even number at the end indicates north-south direction.
NH 9: Odd number at the end indicates east-west direction.
NH 216: Primary NH number is 16 i.e. north-south direction (Kolkata to Chennai) and the prefix 2 suggests NH 216 is a secondary route (Kattipudi to Ongole – both in Andhra Pradesh) in north-south direction.
NH 153: Primary NH number is 53 i.e. east-west direction (Hajira-Surat in Gujarat to Paradip Port in Odisha) and the prefix 1 suggests NH 153 is a secondary route (Saraipali to Raigarh) – both in Chhattisgarh) in east west direction.
Primary NH are either single or double digit, and secondary routes are three digits. If there is an alphabet used as a suffix to the NH, it suggests further shoot off from the secondary highway i.e. an arterial road.
How Are NH Numbers Assigned?
For highways going north-south, even numbers are assigned, and the numbers keeps increasing as we move from east to west. For example, NH 16 is in the east, NH 44 is the middle and NH 66 is in the western part of India.
Odd numbers are assigned to NH going from east to west, and the number keeps increasing as we go from north to south. For example, NH 5 is in Himanchal-Punjab corridor, NH 45 is in central India and NH 85 is in south India.