Optimality gap of experts' decisions in concrete delivery dispatching

•Examining the optimality gap of experts' decisions in concrete delivery.•Comparing exact and heuristic solutions to determine the best available solutions.•Comparing the best available solution with experts' decision to determine the quality of experts' decision in concrete delivery context.

Concrete delivery dispatching suffers from a lack of practical solutions and therefore, in the absence of automatic solutions, experts are hired to handle this task. In addition, the concrete delivery dispatching problem can be modelled mathematically but it can only solve up to medium sizes of this problem within a practical time. This paper attempts to answer the question of how much we can rely on experts' decisions. First, the concrete delivery problem is presented. Second, a benchmark for the problem is achieved; two heuristic methods are used for those instances that their exact solutions are not available. Finally, the experts' decisions are compared with the obtained benchmarks to assess the optimality gap of the experts. A field dataset which belongs to an active Ready Mixed Concrete (RMC) is used to evaluate the proposed idea. The results show that experts' decisions are near to optimum, with an average accuracy of 90%. However, after comparing individual decisions between optimisation models and the experts' decisions, we can conclude that optimisation models only try to achieve the lowest cost, while the expert prefers a more stable dispatching system at slightly higher cost.