The National Highways Authority of India (NHAI) has signed a concession agreement for four-laning the Ambala-Chandigarh section of national highway (NH) 21 and 22. The agreement was signed by NHAI with GMR Ambala Chandigarh Expressway Pvt Ltd, earlier this week. The agreement involves the highest negative grant so far received by NHAI under NHDP-phase III A, i.e. the concessionaire GMR Ambala Chandigarh Expressway Pvt Ltd, would pay NHAI a grant of Rs 105.858 crores (net present value discounted @ 10%), during a concession period of 20 years.