An algorithm for finding reasonable paths in transit networks

In this paper, reasonable paths in transit networks are defined as possible paths that satisfy the acceptable time criterion and transfer‐walk criterion. A recursive algorithm for finding all of the reasonable paths in a transit network that does not involve a rapid increase in program run‐time with network size is presented. Realistic transit networks in Hong Kong and Guangzhou were selected as case studies of the different phases of the development of a trip planning system. Transport planning practitioners and potential users were invited to test the system to evaluate its performance. The results of the prototype evaluation were satisfactory, and the viability of the system as a useful tool for supporting decision‐making has been confirmed by the positive feedback that was obtained from survey questionnaires.     

Quantitative evaluation of passenger terminal orientation

When passenger terminal layout is being decided, one of the important aspects to consider is how the passenger orients himself during his visit to the terminal and his movements through it, i.e. terminal orientation. Among other things, this terminal characteristic results from visibility, or the visual connectivity between elements and spaces. The paper proposes an amendment and modification to the known method for the quantitative evaluation of terminal orientation which uses an oriented network to describe the connectivity of elements (terminal orientation). The amendment and modification of the method consists of proposing that during evaluation only visual connections that have functional meaning should be considered, rather than all visual connections. A further modification is the introduction of different weights for different connections. The example presented in the paper considers an airport terminal building.     

Sea Cucumber Moratorium and Livelihood Diversity in Papua New Guinea

Livelihood diversity factors such as flexibility within fisheries, geographical mobility, reallocation of fishing effort into the broader economy, and the non-material benefits that fisheries provide are important areas of research in marine policy. We use two small-scale fisheries related socio-economic surveys of communities in the Tigak Islands of Papua New Guinea. The first conducted 5 years before a ban on the harvesting of sea cucumbers was imposed and the second from the present day, 5 years after the initiation of the ban—with the objectives of exploring changes in household fishing strategies (types and numbers of species targeted) and to identify any important socioeconomic factors that help explain those changes. Fishing's contribution to total household income has increased significantly (p = 0.019) up from 61% in 2004 to 73% in 2014 with the percentage of female residents living in a household now positively and significantly (p = 0.018) associated with fishing income. The average number of species categories targeted per household increased insignificantly while households with more women are significantly (p = 0.018) less likely to target more species than households with more men. Moreover, customary management practices contribute to this difference. Together, these results show that households are not worse off financially 5 years after the ban on sea cucumber harvesting and that gendered seascape use has implications for the role of livelihood diversity as a marine policy tool.     

GPS-based optimization of plug-in hybrid electric vehicles’ power demands in a cold weather city

Using the WPG03 duty cycle developed from global positioning data collected in Winnipeg, Canada, real world energy demands and costs are modeled. Three types of plug-in hybrid electric vehicles, four temperatures and two charging scenarios are compared to a vehicle with an internal combustion engine. Cold temperatures are shown to greatly affect vehicle operation energy costs, which is an important consideration for cold weather cities such as Winnipeg. The largest energy cost savings are obtained for smaller-battery plug-in hybrids that had the opportunity to charge during the day.     

Genetics of traffic assignment models for strategic transport planning

This paper presents a review and classification of traffic assignment models for strategic transport planning purposes by using concepts analogous to genetics in biology. Traffic assignment models share the same theoretical framework (DNA), but differ in capability (genes). We argue that all traffic assignment models can be described by three genes. The first gene determines the spatial capability (unrestricted, capacity restrained, capacity constrained, and capacity and storage constrained) described by four spatial assumptions (shape of the fundamental diagram, capacity constraints, storage constraints, and turn flow restrictions). The second gene determines the temporal capability (static, semi-dynamic, and dynamic) described by three temporal assumptions (wave speeds, vehicle propagation speeds, and residual traffic transfer). The third gene determines the behavioural capability (all-or-nothing, one shot, and equilibrium) described by two behavioural assumptions (decision-making and travel time consideration). This classification provides a deeper understanding of the often implicit assumptions made in traffic assignment models described in the literature. It further allows for comparing different models in terms of functionality, and paves the way for developing novel traffic assignment models.     

Estimation of origin‐destination matrices for a multimodal public transit network

This paper presents a procedure for the estimation of origin‐destination (O‐D) matrices for a multimodal public transit network. The system consists of a number of favored public transit modes that are obtained from a modal split process in a traditional four‐step transportation model. The demand of each favored mode is assigned to the multimodal network, which is comprised of a set of connected links of different public transit modes. An entropy maximization procedure is proposed to simultaneously estimate the O‐D demand matrices of all favored modes, which are consistent with target data sets such as the boarding counts and line segment flows that are observed directly in the network. A case study of the Hong Kong multimodal transit network is used to demonstrate the effectiveness of the proposed methodology.     

1/32° real-time global ocean prediction and value-added over 1/16° resolution

A 1/32° global ocean nowcast/forecast system has been developed by the Naval Research Laboratory at the Stennis Space Center. It started running at the Naval Oceanographic Office in near real-time on 1 Nov. 2003 and has been running daily in real-time since 1 Mar. 2005. It became an operational system on 6 March 2006, replacing the existing 1/16° system which ceased operation on 12 March 2006. Both systems use the NRL Layered Ocean Model (NLOM) with assimilation of sea surface height from satellite altimeters and sea surface temperature from multi-channel satellite infrared radiometers. Real-time and archived results are available online at http://www.ocean.nrlssc.navy.mil/global_nlom. The 1/32° system has improvements over the earlier system that can be grouped into two categories: (1) better resolution and representation of dynamical processes and (2) design modifications. The design modifications are the result of accrued knowledge since the development of the earlier 1/16° system. The improved horizontal resolution of the 1/32° system has significant dynamical benefits which increase the ability of the model to accurately nowcast and skillfully forecast. At the finer resolution, current pathways and their transports become more accurate, the sea surface height (SSH) variability increases and becomes more realistic and even the global ocean circulation experiences some changes (including inter-basin exchange). These improvements make the 1/32° system a better dynamical interpolator of assimilated satellite altimeter track data, using a one-day model forecast as the first guess. The result is quantitatively more accurate nowcasts, as is illustrated by several model-data comparisons. Based on comparisons with ocean color imagery in the northwestern Arabian Sea and the Gulf of Oman, the 1/32° system has even demonstrated the ability to map small eddies, 25–75 km in diameter, with 70% reliability and a median eddy center location error of 22.5 km, a surprising and unanticipated result from assimilation of altimeter track data. For all of the eddies (50% small eddies), the reliability was 80% and the median eddy center location error was 29 km. The 1/32° system also exhibits improved forecast skill in relation to the 1/16° system. This is due to (a) a more accurate initial condition for the forecast and (b) better resolution and representation of critical dynamical processes (such as upper ocean – topographic coupling via mesoscale flow instabilities) which allow the model to more accurately evolve these features in time while running in forecast mode (forecast atmospheric forcing for the first 5 days, then gradually reverting toward climatology for the remainder of the 30-day forecast period). At 1/32° resolution, forecast SSH generally compares better with unassimilated observations and the anomaly correlation of the forecast SSH exceeds that from persistence by a larger amount than found in the 1/16° system.     

Train-Track Interaction and Mechanisms of Irregular Wear on Wheel and Rail Surfaces

Summary High-frequency train-track interaction and mechanisms of wheel/rail wear that is non-uniform in magnitude around/along the running surface are surveyed. Causes, consequences and suggested remedies to relieve the problems are discussed for three types of irregular wheel/rail wear: (1) short-pitch rail corrugation on tangent tracks and large radius curves, (2) wheel corrugation as caused by tread braking, and (3) wheel polygonalisation. The state-of-the-art in modelling of dynamic train-track interaction in conjunction with prediction of irregular wear is reviewed.     

Quantifying erosion rates and stability of bottom sediments at mussel aquaculture sites in Prince Edward Island,Canada

Downward fluxes of organic biodeposits under suspended mussel culture cause benthic impacts such as microbial mat production. Quantifying sediment erosion in these coastal ecosystems is important for understanding how fluxes of organic matter and particulates contribute to benthic–pelagic coupling. Critical shear velocity (u?), erosion rates and particle size distributions of resuspended sediment were measured at two sites; an impacted muddy site with extensive mussel culture (site 1), and a coarser sandier site with less mussel influence (site 2), using a new method for assessing sediment erosion at Tracadie Bay, Prince Edward Island in August 2003. Shear forces were generated by vertically oscillating a perforated disc at controlled frequencies. These forces correspond to shear velocity, using a re-designed and calibrated Particle Erosion Simulator. Undisturbed sediment cores obtained by divers and grab (sub-cored using a Plexiglas? cores) were exposed to shear stress to compare differences between collection methods. Microbial mats were present at site 1 which initially biostabilized sediment against erosion due to ‘armoring’ of the sediment, but onset of erosion was abrupt once these mats failed. Erosion sequences at site 2 (without mat cover) were smoother resulting in less material being eroded. Mean mass of material eroded was 47 and 23 g m^? 2 min^? 1 at sites 1 and 2 respectively. Mat area cover and shear velocity was strongly related. Critical shear velocities varied between 1.70 and 1.77 cm s^? 1, with no obvious differences between location or collection method, so sediments from these two contrasting sites had identical mean critical shear velocities. Significant differences existed in the concentrations of chlorophyll a, colloidal and bulk carbohydrates, between mats and bare sediment from site 1. Particle sizes measured by videography of resuspended sediment at different shear velocities ranged from 100 μm (the minimum diameter capable of being detected by the system), to large mat fragments of 1700 μm for both sites. These results provide evidence of the relevance of using a portable erosion device to indicate how sediment erodability is affected by mussel–microbial relationships.