Diamond Head hiking trail, Honolulu, Hawaii: Reservation system introduced to control crowds on trail

A spur-of-the-moment hike up Honolulu's Diamond Head is to become a thing of the past, with a reservation system being introduced to help protect this popular trail.

It looms over the city of Honolulu like an alien mothership, its theatrical curtain of ridges plummeting into the intense blue ocean, applauded by a dress circle of skyscrapers. Diamond Head - or Lē'ahi, as it's known in Hawaiian, referring to its shape resembling a tuna dorsal fin - is the most dominant landform on the Waikiki coastline, its saucer-shaped crater a remnant of the long-dormant Ko'olau volcano and a sacred place of sacrifice for ancient Hawaiians.

It's also a designated National Natural Landmark, a former military lookout and one of the most visited attractions in Hawaii, with a record 6000 visitors making the trek to its summit on a single day in 2019.

Several weeks ago, I too joined the throng at the 192-hectare Diamond Head State Monument, the spontaneous decision for an early-morning hike made over cocktails the previous evening as I watched the mountain's barren escarpment illuminate under the setting sun. We arrive at the trailhead at 7.30am, nabbing the last available parking spot; and after paying the $US10 ($A14.60) parking fee and $US5 entry for non-residents (payable at a machine by credit card only), we commence the short but strenuous haul, a 1.28 kilometre heart-starter that gains 170 metres in altitude up steep switchbacks and a series of steps.

Even at this early hour, it's slow going: a solid line of hikers snakes up the path, some struggling under the challenge, faces red and sweating from exertion. But the effort – and bottleneck we contend with at the peak - is worth it: the view – once the crowd clears - is incredible, the city of Honolulu and the waves of Waikiki glistening in the distance creating the perfect backdrop for our selfie.

According to our local guide, this is a quiet day on the trail; even so, it's apparent that this volume of hikers is unsustainable. Physical distancing is impossible to maintain; and I can't begin to imagine the congestion during a hot, sunny day in peak season.

But the unregulated crowds at Diamond Head is now a thing of the past; as are spur-of-moment decisions like ours to squeeze in a brisk morning hike. As of May 12, out-of-state visitors must make an online reservation to visit the park, with their time inside limited to two hours. Parking must also be reserved, with bookings made up to 14 days in advance (this will be extended to 30 days in the future). Locals, however, are exempt from the ticketing system; they can also continue to climb for free.

The new strategy by Hawaii's State Parks has been introduced to lower the impact on the trail, ease car park congestion and to make the hiking experience more pleasant. A similar reservation system has also ready been implemented at Haena State Park on Kauai and at Waanapanapa State Park on Maui.