The financial risks of investment in infrastructure are important investment projects of this kind. Values are very large amounts to invest may be of little phase and the amounts are invested before the first earnings to be seen. Furthermore, traffic (and hence incomes) grow naturally over time, and lower depreciation rates. On the other hand, revenue projections are very difficult. It is difficult to predict the interest that it will pursue new infrastructure. It is almost impossible to predict the optimal level of payment can be accepted by the user. To optimize this payment is required a departure from the economic theory of maximization of surplus, to incorporate criteria psychological perception of global supply and road tax that a user has. For large facilities for traffic, state involvement is essential. Direct financial return is often weak and negative implications for the community are often important
