## 4 Review of Literature
### Supply and Delivery in Routing Optimisation Problems
#### 4.1.3 Heuristics and Local Search in Supply and Delivery VRPs
A large scale disaster response by coordinating an inter-modal network of both helicopters and vehicles is studied by [53]. Because of the limited number of helicopters, supplying directly to Medical Aid Points (MAPs) is considered impossible leading to the cooperation between helicopters and vehicles in delivering the emergency supplies. Referring to their previous work, refs. [53; 54] further stated that the classical Fuzzy C Means (FCM), as applied in their earlier work, tends to ignore the balance of capacity, which could lead to huge wastage of medical supplies. Motivated by these problems of employing FCM, ref. [53] proposed two improved FCM by introducing FCM with Capacity Constraint (FCMwCC) as well as FCM with Number Constraint (FCMwNC). The FCMwCC works with additional proposed heuristics in assigning MAPs to each EDC, since the newly introduced capacity constraint prevents the usual iteration of FCM. FCMwNC, on the other hand, assigns a specific value to the numbers of MAPs assigned to each EDC preventing the unbalance assignment, as in their earlier work. Simulated instances are generated in order to validate the solution and model showing balance distribution, which leads to improved fairness as well as efficient distribution. The HL problem is presented in [55], where the total travel cost is minimised by synchronising the on site visit with delivery of medical supplies. The real case of the Democratic Republic of Congo (DR Congo) is taken to present the two problems that are faced by the hospital administration in maintaining the pharmacy in a rural hospital as well as the high cost of dropping and picking up a supervisor for an on site visit to rural hospital. The problem is addressed by CVRP with synchronised Pick-ups and Drop-offs (CVRP-syncPD). A heuristic method is developed that is based on a cluster first and route later technique with the ability to adapt the synchronisation between pick up and drop off for an aircraft carrier and on site supervisor. The hospitals are clustered according to the capacity constraint, creating a set of medical routes. The synchronised route is later chosen from this set of medical routes by comparing the synchronisation requirement for on site supervision. These synchronised routes are then evaluated in order to minimise the total cost incurred. The test instance for validating the model and solution is based on the Bandundu province, where 41 hospitals are located. The Inventory Slack Routing Problem (ISRP) during a disaster where the inventory of relief item is kept under tight observation for fear of shortage of aid is considered in [56]. The problem is solved by decomposing it into two sub-problems to deal with the routing problem and the inventory problem respectively. From the routing side, the Hierarchy TSP concept is applied where the delivery of one vehicle to a cluster of dispensing sites should be done based on priority on the urgency of the demands. By decomposing the problem, the objective of maximising the minimum slack is now converted to a new objective, which is to minimise the delivery time weighted by priority of the dispensing site. The routing is then solved through the hierarchy routing heuristic or sweep algorithm. Consequently, the allocation problem is then solved directly by solving the resulting converted LP model of the allocation problem. From the computational results, the sweep algorithm outperformed the hierarchy routing heuristic, judging from the resulting total travel time as well as the minimal slack. Ref. [57] focused on the fair allocation of perishable food to ease the problem of hunger in a humanitarian crisis by addressing the problem through the perspective of the ALRP. The problem is based on PDVRP, where waste is avoided while ensuring fair allocation to welfare organisation via optimal route. The envy free allocation could be obtained through the known min-max fair share algorithm.