Average duration and performance of actuated signal phases

This paper describes an approach for evaluating alternative traffic detection designs for a signalized intersection. The models described in this paper can be used to determine the average phase duration and frequency of phase “max-out” as a function of the detector loop layout, detector unit timing, traffic demand, and approach speed. Layout and timing are described by the number of detectors on each approach served by the phase, detector location on each approach, detector length, and detector unit and controller time settings. The authors have used the concept of maximum allowable headway (MAH) to combine the many possible combinations of layout and timing variables into one representative quantity, which greatly simplifies the modelling process. The performance models were used to examine the sensitivity of intersection performance to a range of design values. In general, both phase duration and cycle length increase with higher demands or larger MAHs. Multiloop (i.e. two or more detection zones per lane) detector designs typically have larger MAHs than designs with one detector loop per lane. Phase duration and cycle length also increase for very low demand levels. In terms of performance, the maximum green duration was found to have a contrary effect at higher flow conditions. Larger maximum greens were found to reduce delays to the phase in service by reducing the probability of max-out but they increased delays to drivers waiting for service.     

The concept of delay

The word delay is so widely used that it may be assumed to be a simple concept which is well understood. It is taken to be a name for wasted time on a journey, but attempts to quantify it in order to use it as a measure of performance of a transportation facility have not given complete satisfaction. Drivers are observed to behave in ways which reveal attitudes to wasted time which differ from those of the researcher. These problems have been reported in many studies but do not seem to have been pursued.This paper discusses the concept of delay. A basic definition leads to problems of measurement which suggest alternative definitions which have more apparent relevance to traffic networks in which more than one cause of delay is of interest. Further speculation about these definitions points to the fact that delay can be either of two separate concepts.In conclusion it is argued that delay should no longer be regarded as an objective quantity capable of direct measurement. Instead of delay being thought the cause of driver annoyance, it should be taken that it is the existence of driver frustration which converts time lost into delay. It is better to define delay as unwanted journey time.     

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.     

Challenges in Collaborative Governance for Coastal Restoration: Lessons from the Caernarvon River Diversion in Louisiana

In an effort to restore deteriorating coastal wetlands in Breton Sound, Louisiana, a diversion of Mississippi River water into the estuarine ecosystem has been operated at Caernarvon, Louisiana, since 1991. The diversion was implemented after a relatively long collaborative planning process beginning in the 1950s. The Caernarvon Interagency Advisory Committee, an official panel of stakeholders, considers scientific aspects of the freshwater inflow and stakeholder inputs in developing an operational plan, which internalizes stakeholder conflicts, while accomplishing goals of restoring the coastal ecosystem. Even though fishery representatives are committee members, local oyster fishers filed lawsuits in federal and state courts from 1994 through 2005, claiming damages to their oyster beds. These lawsuits were initially successful in state courts but were reversed by the Louisiana Supreme Court. The federal suits were unsuccessful. Following these lawsuits, voters in Louisiana in 2000 amended the State Constitution to protect coastal restoration projects against lawsuits reflecting increase in overall statewide support. Increasing scientific knowledge has contributed significantly to diversion operation. For better collaborative governance, efforts to increase common understanding among stakeholders will be needed, and a process to compensate interests of stakeholders suffering from impacts of restoration projects at an earlier stage should be institutionalized.     

A meta-analysis of DEA and SFA studies of the technical efficiency of seaports: A comparison of fixed and random-effects regression models

This paper presents a meta-analysis of variations in seaports’ Mean Technical Efficiency (MTE) scores based on 40 studies published in refereed academic journals. We link the variation in estimated MTE scores to differences in the following factors: the frontier methodology used, which essentially are the Data Envelopment Analysis (DEA) and the Stochastic Frontier Analysis (SFA); regions where seaports are situated; type of data used; number of observations; and the total number of variables used. Furthermore, we compare fixed-effects against a random-effects regression model where the latter assumes that the individual study specific characteristics matter while the former assumes that there is one general tendency across all studies. We present several findings based on the data: (1) the random-effects model outperforms the fixed effects model in explaining the variations in MTEs, (2) recently published studies have lower MTE scores as compared with earlier published studies, (3) studies that used nonparametric DEA models depict higher MTE scores as compared with those that used SFA models, (4) panel data studies have lower TE scores as compared with cross-sectional data, and (5) studies using European seaport data produce lower MTE scores when compared with the rest of the world. Finally, our results contradict some previous meta-analysis studies of TE scores. We encourage the use of random-effects models in meta-analysis studies because they account for individual study specific effects.     

Emissions of particulate matters from railways – Emission factors and condition monitoring

We report tunnel measurements, where abrasion particles from different types of trains are measured in two situations and emission factors are calculated from these. The measurements show significantly elevated particle concentrations in train passages that last for about a minute and are accompanied by increased airflow. The emission of particles for each train passage was obtained by summing the product of the particle concentration and the airflow and then multiplying with the tunnel area. The average emission factors were calculated for three categories freight trains, commuter trains and regional trains and found to be 2.9 g/train-km (0.7 – 9), 0.48 (0.1 – 1.6) and 0.24 (0.05–0.9), respectively. The number in brackets refers to the range of values observed. The size-resolved data showed maxima around 1 μm for all three train types.     

Lancaster sound regional study: Coastal and marine resource planning in the Canadian high arctic

Abstract

The Lancaster Sound Regional Study serves as a pilot project for regional planning in the Arctic. Probably the most biologically productive area of all arctic regions, Lancaster Sound represents a unique Canadian heritage. And since it occupies the strategic eastern entrance to the Northwest Passage, the Sound has long been a summer shipping route. Now, proposals are under review that would permit year‐round shipping of oil and gas from the Beaufort Sea by means of ice‐breaking tankers. Also proposed are the exploration and development of possible hydrocarbon reservoirs within the Sound. Actual decisions for the area's use must respect the interests of the native Inuit who have lived there for centuries as well as the preservation of the environment. This paper describes the preliminary phase of the regional planning for the region: the preparation of a public discussion paper to elicit informed comment and opinion on future uses of the Sound. It is a first step toward recommending suitable management and use options for the region.     

Learning Frontiers in the Practice of Integrated Coastal Management

Since the Rio conference in 1992 investments in integrated coastal management (ICM) have increased dramatically. National and subnational governments have undertaken many initiatives to protect and develop coastal areas. Extensive field experience has advanced understanding of the operational attributes of ICM. This article reviews the principles and operational attributes of ICM that have become well accepted, particularly from the perspective of international ICM donors and professionals. A common understanding of the fundamentals of ICM provides a base from which targeted and systematic study and assessment of ICM can be conducted. Several thematic areas are suggested where there are currently important needs and opportunities for collective study and learning in ICM. The important role of donors is emphasized in supporting collaborative learning initiatives that advance understanding of ICM, and improve and expand the practice.