(a) A separate general ledger shall be maintained for each State-aided project as defined in Part 1640 of this Subchapter. Accounts to be maintained in the general ledger are grouped into two major categories, as follows:

(b) In addition to the accounts included in the above categories, the general ledger contains two control accounts, as follows:

(c) Within each major category, the accounts are further grouped by type. The chart of accounts which follows includes, of course, both the accounts which are actually to be maintained in the general ledger and the headings for groups and subgroups of such accounts. Accounts designating group headings are not maintained in the general ledger and are distinguished from the accounts to be maintained in the general ledger by underlining of both the designation [sic]. In a few instances, the use of the subaccounts in a group has been made optional. In such cases, the group headings may be the account to be maintained in the general ledger, depending on the option exercised.