The Arrivals and Departures section of the event graph has people arrive at a random rate whose mean depends upon the time of day and has percentage of the skiers who reach the base leave the resort. This percentage is dependent upon the time of the day. The first Skier Arrives event is called by arrow at the bottom which comes from the Load Data event. The Skier Arrives event will call itself so long as there are 2 or more hours before the resort closes. The time between arrivals of skiers is a exponential distribution with an upper bound and a time dependent mean. When a skier arrives, they are sent to the ski resort Base. A skier may reach the Base by arriving at the resort or taking a ski trail which ends at the Base; this is represented by the arrow coming into Base from the right that is called by the Trailhead event. Anytime a skier reaches the Base, a time dependent probability calculation determines if they will depart or continue skiing. If the skier departs they go to the Depart event and leave the resort. If the skier doesn't depart, the arrow leaving Base to the right sends them to the Probability Calc event to determine which lift or run they take from the base.