3.3. Uncontrolled arrivals
The assumption underlying uncontrolled arrivals is that – in contrast to both stock-controlled and equidistant arrivals – there is no control by plant management over the intervals at which ships arrive. In that case, opting for a Poisson process is the logical choice. This does imply that the number of ar- rivals per year can vary. In the process industry, however, annual throughput is more or less fixed. As a consequence, in our model, the total number of arrivals per year within each ship type is fixed across all arrival processes. This implies that, if the distribution function of interarrival times is exponential, the arrival times are uniformly distributed (Banks, 2000). When simulating uncontrolled arrivals, we therefore draw the arrival times per ship type from a uniform distribution over the year