An analysis of dual-command operations in common warehouse designs

In a warehouse that uses dual-command operations, workers travel loaded from the pickup and deposit (P&D) point first to a location to store a pallet, then to a second location from which they pick a pallet and return to the P&D point. We develop expected travel distance expressions for such operations and use them to analyze three common warehouse designs. Our results indicate that the best of the three is – in our experience – the one least commonly found in practice. We also show that the optimal placement of a “middle cross aisle” in the most common design is, in fact, not in the middle.     

Progressing road safety through deep change and transformational leadership

In an earlier paper in this journal, we argued that current road safety programs and thinking are constructed within a paradigm that tends to accept existing cultural arrangements. The current paper is a sequel to the earlier one, and outlines significant policy themes emerging from a research project on a holistic approach to road safety. Two overarching themes include the importance of leadership for policy change and implementation, and addressing the more transformative aspects of intervening in a system. A distinction can be drawn between “deep” sustainable change, which usually requires fundamental redesign of the systems involved, and “shallow” adaptive change. Examples of deep change discussed include the much wider application of mobility management, a strong shift to active travel and public transport, and a reconsideration of how time is structured in society, as with the adoption of “Slow Cities” principles. Transformational leadership can draw on a variety of “knowledge cultures”, which can all share in collective decision-making and possible actions for the future. We discuss especially leadership at the worldview, organisational, and community levels. Vision Zero approaches are valuable, but need to be integrated with a common vision for a sustainable transport system developed in conjunction with energy, transport, health, environment, and education agencies. In addition, Vision Zero approaches can be assisted by greater attention to and questioning of embedded cultural practices and behaviour.     

Calculations of the shares of financial resources paid by actual payers for transportation improvements

In this paper we identify and quantitatively describe the actual providers of financial resources, termed “actual payers”, for transportation improvements in some advanced countries, using various statistical data. The theoretical framework on which the concept of actual payers is based was presented in our earlier paper (Transport Policy, April 1998). The current study presents the results of calculations performed according to that concept. Because of the complexity and variety of the financial resources drawn on by transportation systems, the means of financial support for transportation have not been made clear when superficial classifications such as “National expenditures”, “Local expenditures”, “Owners/operators' funds” and “Debt” are used. In the present study, the financial support for transportation is calculated on the basis of what is spent by actual payers, such as users, payers of national taxes and payers of local taxes. This approach allows us to show that the shares of actual payers are quite different in each country. In addition, we indicate the characteristics of the shares of the actual payers in each country by calculating the ratio of the users' burden or the dependence of debt, etc.     

UK regional airport commercialisation and privatisation: 25 years on

It has been 25 years since the UK was the first country to begin the process of commercialising and privatising its airports. The purpose of this paper is to revisit the UK Government’s stated aims with respect to commercialisation and privatisation, namely to “encourage enterprise and efficiency in the operation of major airports … [and that] … air transport facilities should not in general be subsidised by the taxpayer … [and they] should normally operate as commercial undertakings.” The authors of this paper consider the success of commercialisation and privatisation against these aims with respect to the 16 UK regional airports commercialised by the 1986 Airports Act part II. In addition, this paper considers the policy ramifications that have eventuated. The authors argue that many of the benefits may have been achievable by commercialisation alone.     

The economic importance of the Straits of Malacca and Singapore: An extreme-scenario analysis

This paper proposes a decision tree model to estimate the loss to global economy on the hypothesis of an extreme scenario of blockade of the Straits of Malacca and Singapore. The insurance surcharges, inventory costs and the time values of cargoes, and Time Charter Equivalent rate are used to estimate the psychological loss, the loss to industries, and the loss to carriers, respectively. Interestingly, there is a pseudo-paradoxical phenomenon with respect to the loss to carriers. An illustrative example is also provided to explain the “Malacca Paradox”.     

Model and algorithm for an unpaired pickup and delivery vehicle routing problem with split loads

This paper addresses the routing problem with unpaired pickup and delivery with split loads. An interesting factor of our problem is that the quantity and place for pickup and delivery are decision variables in the network. We develop an easy-to-implement heuristic in order to gain an efficient and feasible solution quickly. Then, a local search algorithm based on the variable neighborhood search (VNS) method is developed to improve the performance of the heuristic. Computational results show that the proposed VNS method is able to obtain an optimal or near optimal solution in reasonable time for the formulated problem.     

Classifying railway stations for strategic transport and land use planning: Context matters!

The classification of railway stations is a potentially powerful tool for strategic transport and land use planning. Existing classifications rely strongly on the indicator “passenger frequency”, which focuses on transport related issues, blending performance with preconditions at a given site. We argue that a classification system for strategic planning should focus on the demands and conditions of the site within which the railway station must function, i.e. system context. Here, we present such a classification system: a cluster analysis of the 1700 Swiss railway stations relying solely on context factors. The resulting classes vary primarily in density (of land use and transport services) and use (commuting, leisure time, tourism). Common geographic patterns and class-specific dynamics are discernable. These results indicate that classification based on the relevant demands and conditions given by context leads to clearly interpretable classes and supports multi-perspective strategic planning for railway stations. The systematic approach allows for a better understanding of the interrelations between railway stations and their context.     

Social distancing in airplane seat assignments

This paper addresses the airplane passengers’ seat assignment problem while practicing social distancing among passengers. We proposed a mixed integer programming model to assign passengers to seats on an airplane in a manner that will respect two types of social distancing. One type of social distancing refers to passengers being seated far enough away from each other. The metric for this type of social distancing is how many passengers are seated so close to each other as to increase the risk of infection. The other type of social distancing refers to the distance between seat assignments and the aisle. That distance influences the health risk involved in passengers and crew members walking down the aisle. Corresponding metrics for both health risks are included in the objective function. To conduct simulation experiments, we define different scenarios distinguishing between the relative level of significance of each type of social distancing. The results suggest the seating assignments that best serve the intention of the scenarios. We also reformulate the initial model to determine seat assignments that maximize the number of passengers boarding an airplane while practicing social distancing among passengers. In the last part of this study, we compare the proposed scenarios with the recommended middle-seat blocking policy presently used by some airlines to keep social distancing among passengers. The results show that the proposed scenarios can provide social distancing among seated passengers similar to the middle-seat blocking policy, while reducing the number of passengers seated close to the aisle of an airplane.     

Travellers’ profiles definition using statistical multivariate analysis of attitudinal variables

This paper aims at presenting a set of travellers’ typologies using attributes characterizing people’s attitude, through an Exploratory Factor Analysis (EFA), and a subsequent cluster analysis (CA), based on the obtained latent constructs. The final goal is to contribute to deepen the knowledge on market segmentation in order to define more people-oriented transport policies, focusing on a medium size Italian city, Alessandria. Six factors have been defined on which the k-means cluster analysis has been applied finding four travellers’ profiles.Results confirm certain hypothesis from behavioural psychological theories. Attitude–behaviour relationships loosen when habits, consolidated in time, do intervene; moreover in small-medium urban context, as opposed to large and dense cities, insufficient transport supply does not favour the use of alternative modes to the motor vehicle, if not to the cost of a great loss in efficiency. In fact, the study shows how significant constraints such as necessity, time saving, and low transport supply (mainly designed around students going to school) are in determining a behavioural change, so that the “right general attitudes” are not sufficient to obtain a real modal shift. This leads to expect opportunistic behaviours, even within a overall positive attitude towards the environment. Actually, that overall positive attitude is not enough to prompt consistent behaviour unless a marked self-control and strong motivation are present. These two features seem to be missing in the interviewed sample of population, unlike what emerges from other studies undertaken in Northern Europe. The geographic location most likely plays a significant role in such a difference. Indeed, cultural background and the prevailing habits of the population may well explain the “slackening” of the bond between moral norms and behaviour, and the subsequent search for surrogates (e.g. the high willingness to pay for environmental protection) to justify the unwillingness to forgo the private vehicle on behalf of more sustainable modes.Finally, our study seems to prove that education could play a key role in transport policy formulation but, moreover, in social policy, as individuals more akin to modal shift are those showing higher levels of instruction.     

On structural inelasticity of modal substitution in freight transport

At the European level there is an increasing focus on how freight transport can be moved from trucks on roads to more environmentally friendly modes such as rail and ship. A large proportion of the transport services between OD pairs, however, cannot be substituted since there is only one alternative available. The paper investigates the magnitude of this “structural inelasticity” of modal substitution in freight transport due to a sparser layout of rail and ship-based freight networks compared to road. In the analysis we use a recent Scandinavian freight demand model covering more than 800 zones. We find that the structural inelasticity is very significant - in particular for transportation over less than 500 km. Moreover, the inelasticity varies greatly with commodity groups and between OD pairs, and it depends strongly on the port and rail infrastructure. The results suggest that pure charging instruments (road pricing for trucks) in many regions will have limited mode substitution impacts. However, if combined with structural changes in terms of improved infrastructure for rail and ship, impacts may be greater.     

Design and planning for green global supply chains under periodic review replenishment policies

We quantify the impact of jointly optimizing strategic network design and tactical inventory planning on the cost and CO₂ emissions of multi-echelon logistics networks. The obtained insights indicate that longer optimized replenishment cycles reduce a node’s transportation cost and CO₂ emissions but increase its inventory costs. Moreover, under a fixed replenishment cycle, a node’s service level increases when supplied by a satellite warehouse. Finally: (i) the costs of implementing optimal green network design decisions could be misleading if inventory planning is neglected, (ii) greening of supply chains could become expensive, (iii) current legislative CO₂ ton prices hardly influence logistics networks.     

The hierarchy of roads, the locality of traffic, and governance

This study investigates the use of road networks both within and outside of home jurisdictions (city (or town) and county of residence) by analyzing GPS data collected in the Minneapolis—Saint Paul metropolitan area. The study tracked volunteers' travel behavior to determine which roads (and thus which class of roads) users chose to accommodate their travel needs. More than half of the travel on county roads and city streets occur outside of one's home city, but most travel is within one's home county. The average share of travel distance in the home county is more than 70% for both county and city streets. The high share, which does not account for non-residents destined for the county to work or shop, e.g., implies that the free rider problem on city and county streets at the county level is minimal. Of particular concern is travel on city roads in cities other than one's own. To the extent that this is to go to a destination in that city, that travel is also local. However, because city and county roads are typically funded by those jurisdictions from land-based sources such as property taxes, through trips with neither end in the city through which they are traveling are in a very real sense “free riders”, and pose a problem. With growing trip lengths and emerging economies of scale in road management, it may be appropriate to consider moving more roads from township, town, or city level to the county level of government.     

Supply and pricing strategies of informal rural transport providers

Informal paratransit operators using a range of vehicle types (including pickup trucks, small buses, and motorcycles) are a major provider of mobility in rural areas of the developing world. The paper describes a mixed method approach used to examine such operators’ decisions about vehicle deployment, route frequency, network organisation, and pricing in three rural districts in South Africa. New evidence is presented showing that the condition of rural roads (both paved and unpaved) affects the quantity and quality of public transport services provided, as well as the fares charged to passengers. This strengthens the case for judicious infrastructure investment as a way of improving rural access and livelihoods, and suggests how this might happen by way of leveraging better private sector responses. We also describe the emergence of a differentiated service hierarchy involving a variety of vehicle types suited to different operating conditions, and based on intentional coordination among operators of minibus and pickup truck (‘bakkie’) services. We argue that governments should promote such coordination and innovation in rural transport markets.     

The joint replenishment and delivery scheduling of the one-warehouse, n-retailer system

We deal with the joint replenishment and delivery scheduling of the one-warehouse, n-retailer system in this paper. We suggest a more flexible policy for the joint replenishment and delivery scheduling of a warehouse compared with the existing researches. We introduce the mathematical model and two efficient algorithms for the joint replenishment and delivery scheduling of the warehouse. Subsequently, we develop the hybrid genetic algorithm (GA) and compare it with two efficient heuristic algorithms for extensive computational experiments. Further, we show the advantages of our GA in dealing easily with resource restrictions.     

Analyzing air cargo flows of international routes: an empirical study of Taiwan Taoyuan International Airport

Air cargo demand is an important aspect of the operation and planning of private and public agencies responsible for airports. While most existing studies in this field include only geo-economic characteristics of airports and their hinterlands as explanatory variables, this study develops a gravity model of air cargo flows by trying to incorporate more factors that might influence international air cargo flows of an airport. The model is developed based on the panel data of air cargo services on scheduled routes at Taiwan Taoyuan International Airport during the years 2004-2007. The results indicate that population, air freight rate and three dummy variables, including the regional economic bloc of the “Chinese Circle”(an informal partnership between Hong Kong, Macao, Taiwan and mainland China), the Open Sky Agreements and long established colonial links, are key determinants of international air cargo flows from/to Taiwan. These results suggest a wider array of factors needs to be considered in policy.     

Dynamic accessibility mapping using floating car data: a network-constrained density estimation approach

The concept of accessibility has been attracting increasing attention from transportation planners and researchers. The goal of “smart growth” is to promote accessibility rather than mobility. Accessibility mapping is a highly effective tool to support smart growth planning. Studies on accessibility mapping and analysis have proliferated over the last decade as Geographic Information Systems (GIS) has been widely adopted to produce accessibility maps. Nevertheless, a major negative aspect of these efforts is the lack of dynamic access measurement. Traffic conditions change significantly over space and time, leading to non-stationary travel time estimation which is central to accessibility measurement. In this paper, we propose a dynamic accessibility measure based on real-time travel speeds that are derived from floating car data (FCD). We introduce a novel integrated access measure to compute accessibility to Points of Interest (POIs) constrained by road networks. POI accessibility measures are obtained by means of both Network Kernel Density Estimation (NKDE) and Network Linear Density Estimation (NLDE). Therefore, we are able to capture temporal dynamics by taking into account speed variability using FCD during peak and off-peak hours on weekdays and weekends. We demonstrate that the proposed approach can capture the spatio-temporal dynamics of accessibility using FCD for Wuhan city in China. Empirical studies were conducted to examine the impacts of density estimation parameters (search bandwidths) and POI weights on the integrated accessibility. We find that search bandwidth and POI weights would impose profound influence on final accessibility values. Experiments also show that NKDE and NLDE would produce significantly different estimation results.     

Experimental test of airplane boarding methods

We report the results of an experimental comparison of airplane boarding methods. This test was conducted in a mock Boeing 757 fuselage, located on a Southern California soundstage, with 12 rows of six seats and a single aisle. Five methods were tested using 72 passengers of various ages. We found a significant reduction in the boarding times of optimized methods over traditional methods. These improved methods, if properly implemented, offer the potential for significant savings to airline companies.     

The geography of warehouses in the São Paulo Metropolitan Region and contributing factors to this spatial distribution

This paper aims to characterize the relocation of warehouses in the São Paulo Metropolitan Region (SPMR) considering the spatial structure of changes in warehouse locations. We also discuss the potential factors that could attract warehouses to their location, especially in peripheral regions. The study encompasses the period between 1992 and 2017 and analyzes the influence of geographical, economics, road infrastructure, municipality service tax rate, cargo theft, and real estate prices on logistics facility location. The results show no evidence of logistics sprawl in SPMR during the studied period, although a small sprawl appeared between 2010 and 2017, moving the barycenter to the Northwestern direction of the SPMR. The main factors that influence the decision to move the warehouses are the low cost of land, lower tax, and a well-served infrastructure with highway intersections. There is a positive spatial correlation between warehouse per capita and cargo theft.     

A new model of luggage storage time while boarding an airplane: An experimental test

The boarding process is on the critical path of the turn-around. Reduction in boarding time can benefit airline carriers and airports and improve passenger satisfaction. However, aisle interference caused by passengers placing their luggage during boarding is a key factor leading to cabin congestion and low boarding efficiency. Therefore, the storage time for the carry-on luggage and its influencing factors is analyzed in this study. An experiment was conducted in a B737-800 model (1/3 size) to explore the factors effecting the time of luggage storage, and a new effective model of luggage storage time is proposed through a significance test and data fitting. The results show that the age of passengers, the type and quantity of luggage, and the existing luggage in the luggage bin have a significant impact on the luggage storage time; the rule of the variation in luggage placing time is similar between young adult passengers and middle aged passengers; the impact of the existing luggage in the overhead bin on the luggage storage time shows a stable trend in the initial period, but with the quantity of the luggage increasing to a certain point, the luggage storage time begins to increase sharply, which is known as a “jump”; and the luggage type has a great influence on the threshold value of jump. The results of the study can provide a reference for airlines to manage cabin luggage to improve boarding efficiency and improve passenger experience.     

The spatial context of transport disadvantage, social exclusion and well-being

Equity has been a major concern of public transport provision and is required by legislation in many countries. Several approaches measure equity in transit supply however none produce a simple system-wide measure of equity performance. A new approach is presented using Lorenz curves to measure the relative supply of transit to the population. Gini coefficients provide a single measure of overall equity using this method. A system-wide assessment of overall transit supply to the population in Melbourne, Australia shows that 70% of the population shares only 19% of the supply (Gini coefficient = .68). When employment is also taken into account, the situation is not much different; 70% of jobs and population share 23% of service (G = .62). In order to gain some understanding of vertical equity, the transit supply was compared between different age, income and vehicle ownership groups. There is some evidence of higher supply for youth and low-income groups in inner Melbourne, and in all parts of Melbourne no-vehicle households lived in areas of higher transit supply. Overall it is unclear how “fair” these distributions are compared to equity in other cities since this is the first time this method has been undertaken. Projects using similar approaches should provide a good basis for establishing comparative equity between cities.