Local naming conventions
Hawaii uses HI-## for all state routes. When working on an area, if you encounter a road with the old State Hwy ## naming in either the principal or alternate name fields, please change that name to the HI-## format, or send a PM to a state manager to alert them. We are now discussing in the forum which segments of major state highways should have the HI-## in the principal field to enable the shield to display and for clarity to visitors using shielded maps, and which should retain their Hawaiian name because of local conventions.
Because most street and highway names are in the Hawaiian language, the editors are conducting a discussion in the forum about the use of diacriticals. The general practice now is to use street names without the diacriticals; the fonts in the editor currently don't fully support them anyway (the kahako is not available). However, where street signage includes them, some names do appear with the 'okina, represented as an apostrophe.
U-turns
In Hawaii, U-turns on *two-way* Primary Street through Major Highway type roads may be enabled if it is explicitly allowed by signage. This is based on county ordinances, such as Section 15.8.4 of the Revised Ordinances of Honolulu (found here), which bars drivers from making a U-turn "upon any street in a business district, upon any highway with three or more lanes, or at any intersection where traffic is controlled by traffic signal lights, except as otherwise permitted by official signs and markings."
Enabling U-turns even on streets where they may be legal has consequences on routing. This would be subject to changes in national guidance, but Hawaii editors should not enable them as a rule.