New Delhi, Feb. 15 :    New Delhi, Feb. 15:  National Highway Authority of India (NHAI) will tap the market for the second time to raise minimum of Rs 500 crore through a bond issue. This will fund various National highway development projects. The bonds issue will open tomorrow. These will be issued through private placement on tap basis. Deepak Das Gupta, chairman of NHAI said, 'The coupon has been fixed at 9.25 per cent, payable annually with a call and put option after three years.'