Oʻahu is the easiest major Hawaiian island to visit without renting a car, but the winning plan is not “take the bus everywhere.” It is a walkable base, a few transit-shaped days, and pickup-based tours or an occasional rideshare when the schedule would otherwise consume the experience.
Skyline and TheBus use the same HOLO fare system. Honolulu’s current adult fare page lists a $3 single fare, free transfers within 2.5 hours when using HOLO, and a $7.50 day cap. Cash does not include transfers, so a HOLO card is usually the practical visitor choice.
