Time-dependent performance approximation of truck handling operations at an air cargo terminal

This paper provides an analytical solution for the time-dependent performance evaluation of truck handling operations at an air cargo terminal. The demand for loading and unloading operations is highly time-dependent and stochastic for two classes of trucks. Two heterogeneous handling facilities with multiple servers are available to handle trucks assuming exponentially distributed processing times. Trucks are routed to a handling facility depending on the current state of the system upon arrival. To approximate the time-dependent behavior of such heterogeneous queueing systems, we develop a stationary backlog-carryover (SBC) approach. A numerical study compares this approach with simulations and demonstrates its applicability to real-world input data

A queueing theoretic approach to set staffing levels in time-dependent dual-class service systems

This article addresses the optimal staffing problem for a nonpreemptive priority queue with two customer classes and a time-dependent arrival rate. The problem is related to several important service settings such as call centers and emergency departments where the customers are grouped into two classes of “high priority” and “low priority,” and the services are typically evaluated according to the proportion of customers who are responded to within targeted response times. To date, only approximation methods have been explored to generate staffing requirements for time-dependent dual-class services, but we propose a tractable numerical approach to evaluate system behavior and generate safe minimum staffing levels using mixed discrete-continuous time Markov chains (MDCTMCs). Our approach is delicate in that it accounts for the behavior of the system under a number of different rules that may be imposed on staff if they are busy when due to leave and involves explicitly calculating delay distributions for two customer classes. Ultimately, we embed our methodology in a proposed extension of the Euler method, coined Euler Pri, that can cope with two customer classes, and use it to recommend staffing levels for the Welsh Ambulance Service Trust (WAST)

Model for estimating and comparing the risk of occurrence accidents and incidents on the level crossings

U radu je određen matematički model sa ciljem proračuna maksimalnog rizika i utvrđivanja pouzdanosti putno-pružnih prelaza. U definisanom inženjerskom okviru, od determinističke do stohastičke granice apstraktnog broja nesreća i nezgoda, nalazi se  proporcija za estimaciju i komparaciju rizika od nastanka nezgoda i nesreća na putno-pružnim prelazima zasnovana na realnim događajima. Moguće je utvrđivanje nivoa bezbednosti za svaki putni prelaz pojedinačno, što predstavlja originalni doprinos u istraživanjima bezbednosti na mestima ukrštaja železničkog i drumskog saobraćaja.This paper is determined a mathematical model to calculate the maximum risk and determine the reliability of level crossings. In the strongly defined engineering framework, from the deterministic to the stochastic limit of the number of theoretical accidents and incidents, there is a proportion for estimating and comparing the risk of accidents and incidents at level crossings based on real occurrences. It is possible to determine the level of safety for each railroad crossing individually, which is an original contribution to safety research at the intersections of railway and road traffi

Planning Border Controls at UK Airports: Quantitative studies into operational decisions and their impact on passengers

This thesis contains three new research projects in the field of airport border control. Utilising unique access to the UK Home Office and Border Force, these studies combine current and historic data of airport border control scenarios with advanced quantitative methods to provide novel analysis of passenger delays and their costs. This analysis is framed in terms of the significant rise in global air passenger numbers in recent decades and the major technological, operational and information changes that have occurred in response. The overall aim has been to consider areas where these new forms of airport border controls may continue to be operating in ways that result in suboptimal outcomes for passengers; in terms of both average wait times and the frequency of ‘unacceptably’ long delays. Whilst there is a vast literature exploring this field in terms of the theoretical impact of new systems of border control, there are few that explore the objectives of operational decisions or provide empirical evidence to evaluate their underlying logic. I attempt to rectify this by exploring three specific elements of the border system, using UK airports as a case study. The first project considers the impact that the stochasticity of flight arrival times has on the risks that long wait times will occur at non-automated border controls. Whilst authorities receive prior information on the number of flights, passengers, and passenger type, it cannot predict exactly what time those flights will arrive. Using stochastic Discrete Event Simulation (DES) of a UK airport terminal, we identify the wide range of border delays that occur from this single variable and suggest the staffing decisions that would be necessary to ameliorate this risk. My second project explores the costs of variances in border processing times by nationality. Using the results of observational research at various UK ports, I establish the average times that different nationalities spend at staffed desks. These are then included in an updated version of our DES model to show the link between processing rates and border delays. Further analysis illustrates the savings that could be achieved from ‘levelling down’ processing times for nationalities facing the highest challenge to their border. The final project switches to analysing newer automated border controls (eGates). Using results from a stated preference survey, I challenge existing valuations of travel time suggested for passengers in these systems and provide new insight into how the full arrival process needs to be considered when costing delays. DES modelling of multiple UK airports is then used to provide examples of how both time and operational costs vary as the level of eGate provision changes. I conclude from these results that the passenger time costs of an undersupply of gates will often significantly exceed the redundant operational costs of an oversupply