Signalized intersections with variable flow rates: II A model for delay estimation

This second part of our work develops a model for delay estimation at intersections whose traffic signal controls are continuously being updated. Generally, these traffic signals are centrally controlled. The foundation for the delay estimation model is based on a queuing theory model called “Preemptive resume discipline for M/G/1 with two priority levels.” This queuing model assumes that two customers arrive at acertain point by a Poisson arrival process, and that one customer has service priority over the second customer. The analogy for the case of intersection control is that the preferred customers are the red lights and the secondary customers are the vehicles. In order to adapt the model to the realistic behavior of vehicle traffic at continuously adjusted signals, components are derived to modify the model. The simulation results of the first part of this work are used to calculate adjustment factors that fairly accurately reproduce the simulated delays. This gives rise to the advantage of using in practice a closed mathematical model, in particular when trying to optimize the operation of signalized intersections at the network level.     

Port reform in Australia: issues in the ownership debate

Australia port reform initiatives have taken on a variety of forms — from out-right sale and transfer of ownership, to the sale of particular assets of infrastructure or services, or to long-term lease arrangements; or in some cases state governments, unable to relinquish control, have opted for corporatization or commercialization strategies. Reform is driven by the belief that ownership impacts on efficiency and efficiency is perceived to suffer if governments either retain ownership or direct control. As a result a major aim of reform is to either remove or distance governments from day to day port operations. The sale of ports removes government control outright and privatized ports are subject to identical regulatory constraints as any company in the private sector. But corporatization strategies are such that government ownership is retained and ports have been transformed into statutory state owned corporations. Effectiveness of this strategy requires legislation to be such that port corporations are free to operate like their private sector counterparts. To date this has not occurred and some serious impediments are emerging which are embedded in legislation and which, rather than reduce, have indeed, increased government control.     

Upstream pollution sources and coastal water quality protection in North Carolina

Abstract

A watershed‐based approach to water quality management is necessary for protecting coastal water quality, but the relative importance of inland pollution sources on estuaries is often overestimated. This can lead to a misallocation of coastal water protection resources and ignorance of coastal zone pollution sources. This overestimation of upstream contributions is attributable to a failure to recognize that many estuaries have little or no inland drainage area, the confusion of basinwide pollutant loading with pollutant delivery to estuaries, the low delivery ratios for many pollutants within drainage basins, and disproportionately high pollutant delivery for sources within the coastal zone. Examples are given from North Carolina. As a general rule, resources expended on pollution control within or near the coastal zone will result in more coastal water quality improvement per unit effort than resources expended upstream.     

Perspectives on the commercial development of landing gear health monitoring systems

The development of health monitoring technologies for aerospace systems creates a number of challenges for the community of engineers and technical specialists as they seek to integrate the technology into well defined working practices. These challenges do not just extend to the technical, but require a number of commercial questions to be addressed. It is of vital importance, that there is a clearly identified need for aerospace health monitoring, both from a technological and commercial viewpoint. If these needs cannot be identified, then any attempt for marketing health monitoring as a necessary future technological requirement is doomed for failure. Health monitoring technology will need to either deliver significant cost saving benefits to the aircraft operator or demonstrated increases in aircraft safety. The objective of the paper is to provide an assessment of the commercial benefits and development of aircraft landing gear health monitoring. The commercial need and challenges for health monitoring systems are explored in this paper within the context of a changing aerospace maintenance industry and the role in which new systems technology will play. The key findings of the research study are that within the aerospace industry there is a desired paradigm shift within aircraft maintenance towards offering maintenance systems with predictive capabilities. This maintenance revolution will not just incorporate new technologies, but will result in aircraft maintenance packages tailored towards individual customer requirements. The study illustrates the state-of-the-art in health monitoring currently restricts aerospace integration and a number of key technical and commercial issues need to be addressed. Predictive health monitoring offers a variety of commercial benefits for maintenance providers, aircraft operators and manufacturers. However, in order for these benefits to be realised increased transparency in maintenance related information is required between these key players.     

Recent advances in automotive technology and the cost-effectiveness of fuel economy improvement

The potential for improving the fuel economy of conventional, gasoline-powered automobiles through optimized application of recent technology advances is analyzed. Results are presented at three levels of technical certainty, ranging from technologies already in use to technologies facing technical constraints (such as emissions control problems) which might inhibit widespread use. A fleet-aggregate, engineering-economic analysis is used to estimate a range of U.S. new car fleet average fuel economy levels achievable given roughly 10 years of lead time. Technology cost estimates are compared to fuel savings in order to determine likely cost-effective levels of fuel economy, which are found to range from 39 miles per gallon to 51 miles per gallon depending on technology certainty level. The corresponding estimated increases in average new car price range from $540 to $790 (1993$). Estimated fuel savings payback times average less than 3 years and the cost of conserved energy averages $0.50 per gallon, indicating that these levels of fuel economy improvement are cost-effective over a vehicle lifetime. A vehicle stock turnover model is used to project the reductions in gasoline consumption and associated emissions that would follow if the estimated fuel economy levels are achieved. Potential trade-offs regarding vehicle performance, safety, and emissions are also discussed.     

Directional Dynamics of a Tractor-Loader-Backhoe

This paper presents a study of the directional dynamics of large industrial tractors. These vehicles have special properties which make their dynamics interesting, including soft rear tires, large yaw moments of inertia and low or negative understeer gradients.

A linear yaw plane model was used for the analysis. The lateral compliance of the tires was included via a simplified version of the stretched-string model. Measurements were performed in support of the modeling effort, including inertial parameters, understeer gradient and transient response. A comparison between calculations and test results indicated that lateral compliance was an important influence on the transient response of these vehicles.     

Influence of turbulence closure models on the vortical flow field around a submarine body undergoing steady drift

Manoeuvring underwater vehicles experience complex three-dimensional flow. Features include stagnation and boundary layer separation along a convex surface. The resulting free vortex sheet rolls up to form a pair of streamwise body vortices. The track and strength of the body vortex pair results in a nonlinear increase in lift as body incidence increases. Consequently, accurate capture of the body vortex pair is essential if the flow field around a manoeuvring submarine and the resulting hydrodynamic loading is to be correctly found. This work highlights the importance of both grid convergence and turbulence closure models (TCMs) to the strength and path of the crossflow-induced body vortices experienced by the DOR submarine model at an incidence angle of 15°. Five TCMs are considered; Spalart–Allmaras, k-ε, k-ω, shear stress transport, and the SSG Reynolds stress model. The SSG Reynolds stress model shows potential improvements in predicting both the path and strength of the body vortex over standard one- and two-equation TCMs based on an eddy viscosity approach.     

Safety outcomes of internationalization of domestic road haulage: a review of the literature

Abstract

The European Union (EU) promotes gradual lifting of restrictions on foreign hauliers involved in domestic road transport of goods (cabotage), and a major deregulation was scheduled in 2014. Due to complaints from several member states facing competition from new EU-countries with lower labour costs, this process was postponed until 2015. An important aspect related to such a deregulatory reform includes potential consequences for transport safety and accident risk factors. The main aims of the current paper are therefore to examine the potential transport safety outcomes of increasing internationalization of domestic road haulage, and to examine potential accident risk factors of foreign hauliers. This is done by reviewing the research literature. This paper shows that the heavy goods vehicle (HGV) accident risk varies with a factor of up to 10 in European countries, and that the accident risk of foreign HGVs is approximately two times higher than that of domestic HGVs in the studied European countries. The paper points to several risk factors and concludes that better data on accident risk and risk factors must be gathered in order to enable European authorities to correctly analyse and respond to this important traffic safety challenge.     

Fatigue in transport: a review of exposure,risks, checks and controls*

Human fatigue continues to threaten safe transport. There are claims that employers of operators should do more to mitigate the risks, and several regulators are promoting fatigue-risk management in the context of safety management systems (SMS). The current paper reviews fatigue-related risk and exposure factors and control measures for operators of land- and sea-based transport forms. Our review identifies 13 types of measures for the monitoring or control of fatigue risks: optimal staffing; optimal schedule design; optimisation of breaks/naps; monitoring of actual hours worked; optimisation of work content; monitoring and feedback of actual sleep; health screening and treatment; promotion of recovery from work; fitness-for-duty testing; monitoring of fatigue symptoms while operating; control of fatigue while operating; performance monitoring and assistance; and fatigue-proofing. We also identify two systemic measures needed to anchor risk mitigation in SMS: organisational learning and training/other. By structuring monitoring and control measures along Dawson and McCulloch’s [Managing fatigue: It’s about sleep. Sleep Medicine Reviews, 9(5), 365–380] fatigue-risk trajectory, a framework is obtained that acts as a guide for fatigue-risk management by transport employers. To inform transport managers further, evaluations are needed of the effectiveness of individual control measures as well as whole fatigue-risk management interventions.     

Making the Australian flag fleet efficient: dysfunctional policy processes and the 'play of power'

In 1997 the Australian government introduced reform measures aimed at improving the efficiency and cost effectiveneess of the Auistralian maritime sector. These measures are part of an ongoing reform programme initiated in the early 1980s; but despite concerted efforts by a succession of governments and the payout of high labour redundancy costs the problems of inefficiency, high costs and low profitability persist. This paper focuses on the structure and mechanism of the policy making processes that have attempted to deal with the problem of making the Australian national flag fleet efficient and competitive. It does so because it is a fundamental tenet of the paper that it is the process of policy making that so frequently—if not invariably—determines policy content and outcomes.