The Tongariro Crossing starts the Mangatepopo Car Park and ends at the Ketetahi Car Park. The best option is to park your vehicle at the Ketetahi car park, which is located very close to the end of the crossing, and includes a one-way shuttle service from there, to the start of the crossing at Mangatepopo. At the end of your hike, you simply walk an extra 900 metres and you are back at your car. If you are relying on a shuttle to get you back to your accommodation, then it means you have to work with the schedule of the shuttle operator. If they leave at 5pm, but you finish your hike at 4.05pm, then you have no choice but to wait for nearly an hour for your shuttle. The car park is fully secure and super convenient.