Performance indicators for public transit connectivity in multi-modal transportation networks

Connectivity plays a crucial role as agencies at the federal and state level focus on expanding the public transit system to meet the demands of a multimodal transportation system. Transit agencies have a need to explore mechanisms to improve connectivity by improving transit service. This requires a systemic approach to develop measures that can prioritize the allocation of funding to locations that provide greater connectivity, or in some cases direct funding towards underperforming areas. The concept of connectivity is well documented in social network literature and to some extent, transportation engineering literature. However, connectivity measures have limited capability to analyze multi-modal public transportation systems which are much more complex in nature than highway networks.In this paper, we propose measures to determine connectivity from a graph theoretical approach for all levels of transit service coverage integrating routes, schedules, socio-economic, demographic and spatial activity patterns. The objective of using connectivity as an indicator is to quantify and evaluate transit service in terms of prioritizing transit locations for funding; providing service delivery strategies, especially for areas with large multi-jurisdictional, multi-modal transit networks; providing an indicator of multi-level transit capacity for planning purposes; assessing the effectiveness and efficiency for node/stop prioritization; and making a user friendly tool to determine locations with highest connectivity while choosing transit as a mode of travel. An example problem shows how the graph theoretical approach can be used as a tool to incorporate transit specific variables in the indicator formulations and compares the advantage of the proposed approach compared to its previous counterparts. Then the proposed framework is applied to the comprehensive transit network in the Washington–Baltimore region. The proposed analysis offers reliable indicators that can be used as tools for determining the transit connectivity of a multimodal transportation network.     

Determinants of vessel-accident bunker spills

The study investigates determinants of vessel-accident bunker fuel spillage. A vessel-accident bunker spillage equation is estimated using Tobit regression and data of individual non-oil-cargo vessel accidents that were investigated by the US Coast Guard during 2001–2008. The results indicate that the bunker spillage of a freight ship and an offshore supply vessel accident will be greater than that of a passenger ship accident. Also, the bunker spillage of a non-oil-cargo vessel accident will be greater if the vessel accident is an abandonment and occurs at night, but less if the accident involves a vessel that has diesel propulsion and even less if the vessel has both diesel propulsion and a steel hull.     

The value of travel time and reliability-evidence from a stated preference survey and actual usage

This research examined travel behavior of Managed Lane (ML) users to better understand the value travelers place on travel time savings and travel time reliability. We also highlight the importance of survey design techniques. These objectives were accomplished through a stated preference survey of Houston’s Katy Freeway travelers. Three stated choice experiment survey design techniques were tested in this study: Bayesian (D_b) efficient, random level attribute generation, and an adaptive random approach. Mixed logit models were developed from responses using each of those designs. The value of travel time savings (VTTSs) estimates do vary across the design strategies, with the VTTS estimates based on the D_b-efficient design being approximately half the estimates from the other two designs. However, among the three design strategies, the value of travel time reliability (VOR) was only significant in the D_b-efficient design.The estimated VTTS from actual Katy Freeway usage (as measured using actual tolls paid and travel time saved on the managed lanes) is $51/h. This likely also includes any value that travelers place on travel time reliability. In comparison, our combined estimate of VTTS and VOR based on the SP survey (D_b-efficient design) was $50/h, which is remarkably close to the estimate from the actual usage data. Based on our dataset, the D_b-efficient design technique proved superior to the other two techniques. Finally, this research also supports the importance of including both travel time and travel time reliability parameters when estimating the willingness to pay for, and therefore benefits derived from, ML travel.     

The optimal dispatching of taxis under congestion: A rolling horizon approach

Taxis make an important contribution to transport in many parts of the world, offering demand‐responsive, door‐to‐door transport. In larger cities, taxis may be hailed on‐street or taken from taxi ranks. Elsewhere, taxis are usually ordered by phone. The objective of a taxi dispatcher is to maximize the efficiency of fleet utilization. While the spatial and temporal distribution of taxi requests has in general a high degree of predictability, real time traffic congestion information can be collected and disseminated to taxis by communication technologies. The efficiency of taxi dispatching may be significantly improved through the anticipation of future requests and traffic conditions. A rolling horizon approach to the optimisation of taxi dispatching is formulated, which takes the stochastic and dynamic nature of the problem into account. Numerical experiments are presented to illustrate the performances of the heuristics, taking the time dependency of travel times and passenger arrivals into account.     

Stress analysis of ventilated brake discs using the finite element method

One of the most common problems related to ventilated brake discs are crack formations, particularly under high brake loads or from the associated stresses during braking. In this study, three different ventilated brake discs, the crossdrilled disc, the cross-slotted disc, and the cross-slotted with a side groove disc, were manufactured, and their braking force performances were investigated experimentally together with a solid disc. Stress analyses were subsequently performed by the finite element method. Analyses results showed that the maximum stress generations were formed on the ventilated discs in comparison to the solid disc. However, these comparisons indicate that the application of varying force distributions along brake pads reduces the stresses on ventilated discs by 8.8% to 19.1%.     

Commuting times – The role of gender,children and part-time work

It has been widely established in the UK and other developed countries that men commute longer than women and that fathers travel furthest to work while mothers travel least. This paper models a wide variety of factors that affect commuting times including gender, presence of children and working hours (part- and full-time work). It finds that of particular importance to the length of commute are the worker’s age, having children, the age of their youngest child, occupation, weekly pay, and mode of transport (with public transport being associated with longer commutes). The region of residence was important for men and women working full-time but not for part timers (except for women in London), while ethnicity and owner occupation were associated with commuting length for full-time men only. The results suggest that while gender, working hours and childcare responsibility are often inter-related, it is useful to disaggregate their effects when modelling or developing policy.     

Consensus Building in Oil Spill Response Planning Using a Fuzzy Comprehensive Evaluation

Major accidental oil spills still affect ecologically and economically sensitive marine areas and shorelines, even though environmental programs and policies have led to an increase of ship safety measures. The aim of decision making during oil spill response management is to minimize pollution effects on coastal areas, once spills occur. However, limited equipments or options prevent such a globally satisfying combat strategy. Thus, often preferences between different coastal areas or uses, respectively, have to be made in an operational way. Such a management issue is here taken as a multigroup multicriteria decision-making problem involving a variety of stakeholders and natural dynamic environments. For solving such a complex problem, this article proposes a second order fuzzy comprehensive evaluation (FCE) model, which takes the influence of multiple criteria and the knowledge of different interested groups into account and further provides a basis for simulating a voting-based decision process. With the combination of oil fate simulations and FCE technique, managers are able to realize an integrated management for oil spill. Through a case study of the Prestige accident off the Spanish coast in 2002, it is demonstrated that the model provides a simple, effective and adaptable method to solve operational management problems related to complex human nature interactions as realized during oil spill management. Moreover, a series of analyses and comparisons are focused on to explore potentials and limitations of the FCE for further applications in the field of multigroup multicriteria decision making.     

Detecting and Managing Coastal Fisheries and Aquaculture Gear Using Satellite Radar Imagery

Fishing and shellfish aquaculture are important sources of income for coastal communities in Thailand and other parts of tropical Asia, but environmental impacts associated with these small-scale activities can effect water quality, nearshore habitats, and fish populations. The management of coastal fisheries and aquaculture has, therefore, become a major concern for government fisheries officials who are searching for cost effective measures to improve the regulation of these sectors. Synthetic aperture radar (SAR) images from the RADARSAT-1 satellite were acquired to determine if stationary fishing and aquaculture gears within a coastal study site in the Upper Gulf of Thailand could be identified, and if automatic signature separation of gear types was possible. The use of SAR imagery for a coastal monitoring application was also evaluated and the potential of this technology to improve resource management outcomes considered.     

Towards an ‘inland terminal centred’ value proposition

The two main value propositions in international container transport are ‘port-to-port’ services and ‘door-to-door’ services. In port-to-port services, buyers ‘just’ purchase maritime transport from a shipping line. Door-to-door services comprise the total transport chain and include land-based transport. Carriers as well as forwarders offer these door-to-door services. In this paper we provide a qualitative assessment of an emerging third value proposition that is centred around inland terminals (ILTs). Such a value proposition consists of transport up to the ILT, and may have advantages over port-to-port services, such as better leverage of scale economies, better repositioning of empty containers and better alignment with the business model of forwarders. This paper conceptually and empirically explores such a value proposition.