The Prime Minister's committee on infrastructure on Thursday gave in principle approval for an investment of Rs 1,70,000 crore for national highway development projects over the next seven years. Under the programme, the onging phase I (golden quadrilateral) and phase II (North-East- East-West) of the NH projects would not only be completed, but "substantial additional work' would be taken up. According to official sources, the committe has decided to conduct a detailed exercise for resource mobilisation for the mega project. It has decided to explore various fund-raising options - including the possibility of leveraging of the existing cess for roads (Rs 1.5/litre on petrol and diesel) for raising substantial immediate resources.