Problem description
The demand for HHC is huge, but the number of nurses is not rising accordingly in Austria. Efficient route plans are therefore required to be able to maintain these services. Currently, the planning is done manually. This leads to an enormous effort and suboptimal tours. With the help of a decision support system the planning should improve in future. As a main service provider, the Austrian Red Cross has hereby an interest that the traveling times as well as the dissatisfaction level of clients and nurses are minimized. Together we defined six aims to measure the dissatisfaction of clients and nurses. As service is personal, clients often prefer to be visited by a particular nurse at a certain time. A lot of nurses work part-time and therefore would like to work at a certain time of the day. Overtime is usually also not preferred as well as visits to clients who require a lower qualification level. Additionally, some nurses do not get paid for the driving time to the first client and back home from the last one. Nevertheless, they have an interest in keeping these driving times small. These aims are combined in a weighted objective function where the weights sum up to 1. The choice of the weights rests with the decision maker(s).
Besides the complexity of the objective function, several constraints have to hold. For a proper description of these and the whole model the properties of the clients and nurses are given in the following.
Each client needs one or more treatments per day. These can include for example medication, insulin shots, and washing. Each treatment is declared as a job. Each job has a certain qualification level , duration , and a time window in which the service has to start. Additionally, the preferred visiting time window is given by and holds. is the preference of a client for a nurse. is the driving time between clients and starting (ending) points.
Each nurse is defined by a qualification level and a contract working time . After a working time of a break is mandatory. The break duration as well as a desired time window for the break can be specified by the nurse for each shift (tour) he/she is working in. Generally, a nurse can work several shifts a day, as long as his/her total working time does not exceed the maximum allowed working time and there is a break between the shifts at least as long as . equals the nurse of shift . For each shift, the nurse would like to work from to . This time window is soft. Due to different work contracts three possible starts of the tours are possible. The nurse might start at the depot , or at home with payment of the complete tour ( ), or at home with payment from the arrival at the first client until the end of the visit of the last client ( ).
Both clients and nurses have different language skills. Four languages with two options, speaking the language or not, are considered. Moreover, a nurse can reject servicing a specific client, and a client can decline a specific nurse, for any reason. A visit is therefore only allowed if the qualification level of the job is lower or equal the qualification level of the nurse, client and nurse speak the same language, and neither the client nor the nurse reject each other.