Trolltunga has three different parking areas.
P1 Tyssedal has 220 places and costs 300 NOK for one day. The estimated walking time from P1 to Trolltunga is 15 hours round trip.
P2 Skjeggedal is the main starting point, has 180 places, and costs 500 NOK per day. Here, the estimated walking time is 8 - 12 hours round trip.
P3 Mågelitopp is a private car park with space for only 30 vehicles. This parking costs 600 NOK for one day, but an additional toll of 200 NOK comes on top. This parking area must be booked in advance! The estimated walking time from P3 is 7-10 hours round trip.
There are shuttle buses between Odda, P1 Tyssedal, and P2 Skjeggedal. From P2 Skjeggedal, there is a shuttle bus on to P3 Mågelitopp.
See here for more detailed information on parking and transportation.