B. The state treasurer shall:

1. 1. Account separately for each account.
2. 2. Make transfers between accounts only as provided in this article or chapter 21, article 2 of this title.
3. 3. Before any bonds are issued, deposit transportation excise tax revenues transferred to the state treasurer in the construction account. These revenues shall be expended as provided in this article.
4. 4. After any bonds are issued, deposit transportation excise tax revenues transferred to the state treasurer in the bond account first until the bond account contains monies sufficient to meet all principal, interest or redemption requirements for the current period as required by any resolution of the board pertaining to the issuance of bonds.
5. 5. After all current period requirements for all of the bonds are deposited in the bond account, deposit the balance of transportation excise tax revenues transferred to the state treasurer for the current period in the construction account.

C. The state treasurer may:

1. 1. Invest monies in any account of the regional area road fund in any securities or obligations authorized by title 35, chapter 2, article 2.
2. 2. For the purpose of investments, commingle monies within the regional area road fund with state monies if all interest earned on the monies in the regional area road fund of a county is credited to the respective account of the regional area road fund in which the investment was made.

D. The department shall separately account for the uses of transportation excise tax revenues deposited into the bond account and the construction account in order to identify how the transportation excise tax revenues are used pursuant to section 42-6105, subsection D, paragraphs 1 and 2, for:

1. 1. Freeways and other routes in the state highway system.
2. 2. Major arterial streets, intersection improvements and regional transportation infrastructure identified in the plan, including capital expense and implementation studies.

E. The department shall separately account for the uses of transportation excise tax revenues deposited in the bond account and the construction account in order to identify how the transportation excise tax revenues are used pursuant to section 42-6105.01, subsection D, paragraphs 1 and 2 for:

1. 1. Freeways and other routes in the state highway system.
2. 2. Major arterial streets, intersection improvements and regional transportation infrastructure identified in the plan, including capital expense and implementation studies.