In the travelling thief problem (TTP) there is a person called “thief“ who wants to make a round trip through a set of different cities. In each of these cities there are different items which have a weight and a profit. These items can be collected in the knapsack which has a maximum capacity. The goal of the thief is to maximize his profits by collecting the most valuable items without exceeding the knapsacks capacity. But by collecting items along the journey the weight of his knapsack increases and therefore decreases his velocity resulting in a longer total travel time. Additionally the thief has to pay a rent for his knapsack which is proportional to the time needed for the tour. The objective of the thief is to find a tour through all cities and a packing plan which maximizes his profit
Reference : https://www.ac.tuwien.ac.at/files/pub/wachter_15.pdf