No abstract

Offshore petroleum industry uses helicopters to transport the employees to and from installations. Takeoff and landing represent a substantial part of the flight risks for passengers. In this paper, we propose and analyze approaches to create a safe flight schedule to perform pickup of employees by several independent flights. Two scenarios are considered. Under the non-split scenario, exactly one visit is allowed to each installation. Under the split scenario, the pickup demand of an installation can be split between several flights. Interesting links between our problem and other problems of combinatorial optimization, e.g., parallel machine scheduling and bin-packing are established. We provide worst-case analysis of the performance of some of our algorithms and report the results of computational experiments conducted on randomly generated instances based on the real sets of installations in the oil fields on the Norwegian continental shelf. This paper is the first attempt to handle takeoff and landing risk in a flight schedule that consists of several flights and lays ground for the study on more advanced and practically relevant models.

Purpose -In the Norwegian offshore oil industry, helicopters have been used as a major mode of transporting personnel to and from offshore installations for decades. Helicopter transportation represents one of the major risks for offshore employees. The purpose of this paper is to study the safety of helicopter transportation in terms of the expected number of fatalities on an operational planning level. Design/methodology/approach -Based on an analysis of helicopter accidents, this paper proposes a mathematical model that can aid in the planning of routes for the fleet in order to minimize the expected number of fatalities. Findings -A theorem proven in this paper tells that hub-and-spoke configuration is the best way of routing helicopters in terms of minimizing expected number of fatalities. Computational results indicate that the expected number of fatalities may be reduced at the expense of longer travel time by implementing the proposed method into planning of routes for helicopter fleet.Research limitations/implications -The main limitation is the present inability to solve large problem instances. Practical implications -The suggested tool is able to provide decision makers with a set of solutions from which they can choose the one with the best trade-off between travel time and transportation safety. Originality/value -The mathematical model and theoretical results for route planning with a safety-based objective are original.

Service network design (SND) is a part of tactical planning activities of transportation companies. Less-than-truckload (LTL) trucking industry has been steadily expanding the market share in the past decades, due to its operational flexibility and high efficiency. In order to provide flexible and robust service schedule for LTL carriers, stochasticity is explicitly taken into account when formulating the SND problem. Service schedules derived from the stochastic model show structural difference with its deterministic counterparts. This research project develops a simulation model of an LTL network, in order to evaluate the system performance of LTL network with the stochastic schedule. A set of experiments shows that the stochastic solution performs very well when it is confronted with random customer demands. Furthermore, the stochastic schedule is much better than the deterministic one in terms of the proportion of undelivered commodities.