On the influence of tyre and structural properties on the stability of bicycles

In recent years the Whipple Carvallo Bicycle Model has been extended to analyse high speed stability of bicycles. Various researchers have developed models taking into account the effects of front frame compliance and tyre properties, nonetheless, a systematic analysis has not been yet carried out. This paper aims at analysing parametrically the influence of front frame compliance and tyre properties on the open loop stability of bicycles. Some indexes based on the eigenvalues of the dynamic system are defined to evaluate quantitatively bicycle stability. The parametric analysis is carried out with a factorial design approach to determine the most influential parameters. A commuting and a racing bicycle are considered and numerical results show different effects of the various parameters on each bicycle. In the commuting bicycle, the tyre properties have greater influence than front frame compliance, and the weave mode has the main effect on stability. Conversely, in the racing bicycle, the front frame compliance parameters have greater influence than tyre properties, and the wobble mode has the main effect on stability.     

The taxi industry: working conditions and health of drivers,a literature review

The taxi industry plays an important role in urban transportation systems, both in economic and mobility terms. In the case of the former, it provides employment for a large number of people and circulates significant amounts of money. In the case of the latter, it is a flexible means of transportation capable of arriving at any destination. Although the way the taxi industry is organised varies across countries and even within countries, some factors are shared at varying latitudes of the globe. Working conditions, habits, health, and exposure to road crashes have been a subject of interest for researchers from various disciplines, including medicine, psychology, and economics. However, much of this research focuses on a part of the problem and is not mutually referential. A review of the literature may be useful not only to researchers of diverse disciplines but also to industry representatives and those public officials responsible for transportation, road safety and health policy. This article provides a comprehensive review of the working conditions of taxi drivers, their relationship to road risk exposure and their consequences on the health of workers. It also includes information on coping strategies and protective behaviors. The review is based on a Scopus database search. The search covered the period from 1990 to 2015. This initial search was complemented with other database searches, which yielded some additional studies. Our goal was to summarise existing knowledge, identify possible lines of research and suggest some practical recommendations. It would be important (a) to reduce the workload, establish adequate time for breaks, and provide access to healthcare, (b) to implement actions to promote and maintain healthy habits, (c) to diagnose, detect and treat indicators of occupational fatigue and stress, and (d) to develop programs that make it possible to evaluate work concerns and broaden coping strategies to foster positive changes.     

Aeronumeric optimal design of a wing-in-ground-effect craft

An optimization technique was used to generate a wing-in-ground-effect (WIG) configuration which can achieve the maximum lift and satisfy the height stability criteria within the design constraints. For the analysis of the aerodynamic coefficients, the vortex lattice method (VLM) was applied with the inviscid and potential flow approximations. The sequential quadratic programming (SQP) method, which is a nonlinear optimization method, was employed as an optimization tool. The lift and moment coefficients, including the stability analysis computed by VLM, were compared with the experimental results of a medium-sized WIG, and a good correlation was found between them. In addition, the optimization tool was validated by finding the optimal position of the side wing attached on the WIG craft. Then, various optimum examples are shown, with generation of the wing section, the determination of the planform configuration, the aspect ratio, and the position of the tail wing within the design constraints. It was shown that the present optimization tool can be used effectively for the optimal design of a WIG craft.     

Comparison between a reanalyzed product by 3-dimensional variational assimilation technique and observations in the Ulleung Basin of the East/Japan Sea

Reanalyzed products from a MOM3-based East Sea Regional Ocean Model with a 3-dimentional variational data assimilation module (DA-ESROM), have been compared with the observed hydrographic and current datasets in the Ulleung Basin (UB) of the East/Japan Sea (EJS). Satellite-borne sea surface temperature and sea surface height data, and in-situ temperature profiles have been assimilated into the DA-ESROM. The performance of the DA-ESROM appears to be efficient enough to be used in an operational ocean forecast system.Comparing with the results from Mitchell et al. [Mitchell, D. A., Watts, D. R., Wimbush, M., Teague, W.J., Tracey, K. L., Book, J. W., Chang, K.-I., Suk, M.-S., Yoon, J.-H., 2005a. Upper circulation patterns in the Ulleung Basin. Deep-Sea Res. II, 52, 1617-1638.], the DA-ESROM fairly well simulates the high variability of the Ulleung Warm Eddy and Dok Cold Eddy as well as the branching of the Tsushima Warm Current in the UB. The overall root-mean-square error between 100 m temperature field reproduced by the DA-ESROM and the observed 100-dbar temperature field is 2.1 °C, and the spatially averaged grid-to-grid correlation between the two temperature fields is high with a mean value of 0.79 for the inter-comparison period.The DA-ESROM reproduces the development of strong southward North Korean Cold Current (NKCC) in summer consistent with the observational results, which is thought to be an improvement of the previous numerical models in the EJS. The reanalyzed products show that the NKCC is about 35 km wide, and flows southward along the Korean coast from spring to summer with maximum monthly mean volume transport of about 0.8 Sv in August–September.     

Unlimited Access

Universities and public transit agencies have together invented an arrangement – called Unlimited Access – that provides fare-free transit service for over 825,000 people. The university typically pays the transit agency an annual lump sum based on expected student ridership, and students simply show their university identification to board the bus. This paper reports the results of a survey of Unlimited Access programs at 35 universities. University officials report that Unlimited Access reduces parking demand, increases students' access to the campus, helps to recruit and retain students, and reduces the cost of attending college. Transit agencies report that Unlimited Access increases ridership, fills empty seats, improves transit service, and reduces the operating cost per rider. Increases in student transit ridership ranged from 71 percent to 200 percent during the first year of Unlimited Access, and growth in subsequent years ranged from 2 percent to 10 percent per year. The universities' average cost for Unlimited Access is $30 per student per year.     

The relationship between segment-level built environment attributes and pedestrian activity around Bogota’s BRT stations

Few studies have examined the relationship between micro-scale features of the built environment and street segment usage. Micro-scale features of the built environment include the width of the sidewalk, the presence of amenities such as benches and trash bins, and the presence of crossing aids such as stoplights and crosswalks. This study employs segment-level primary data collected for 338 street segments in close proximity to one of 71 bus rapid transit stations in Bogotá, Colombia. We also use secondary data to control for area-level characteristics such as density, socio-economic stratum, unemployment, and crime. Factor and regression analyses are to use identify two dimensions of the built environment that are associated with higher levels of pedestrian activity: pedestrian-friendly amenities, comprised of wider and higher quality sidewalks and the presence of amenities such as benches, garbage cans, and bike paths; and connectivity, comprised of higher levels of road density, three- and four-way intersections, and density. In addition, we find greater pedestrian activity on segments with higher development intensity, with more mix of land uses, and with more crossing aids. Although the relationships identified are not causal, they are suggestive in terms of planning successful built environment interventions.     

A bus route evaluation model based on GIS and super-efficient data envelopment analysis

When compared to large cities in developed countries, the shares of public transportation in most Chinese cities are low. Increasing the competitiveness of urban public transportation remains an urgent problem. A capable evaluation method for public transportation is required to assist the development of urban transit systems. This paper focuses on the bus system. Being devoid of standard criteria, it is difficult to determine the efficiency of a transit system or any bus line using a single evaluation index. This paper proposes a comparative analysis to evaluate bus lines so as to filter out candidates for further optimization. From the viewpoints of transit planning, operation and quality of service, this paper establishes 10 subordinate evaluation indices and then uses geographical information system tools, global positioning system data and smart card data to assist the index definition and calculation. Super-efficient data envelopment analysis (DEA) method is adopted for the proposed single factor and comprehensive evaluation models. Finally, the bus system in Shenzhen, China is used as a case study. The comparable significant results validate the capability of the proposed model.     

Land requirements for public transport facilities in urban areas—A statistical approach

The major aim of this work is to develop a primary tool for the quantitative determination of land areas needed to fulfil the diverse functions of public transport. The need for such a tool is obvious; worldwide there is a lack of criteria for determining the types of areas needed, their size, and relative location in the urban system. Moreover, there is a lack of awareness regarding land allocation during the various planning stages, both by urban planners and decision makers. This work attempts to identify various types of facilities to be allocated within the urban framework, and to determine quantitative guidelines for the land needed for them. A statistical analysis is performed in order (i) to identify major transit facilities and operational data functions for which land must be allocated, and (ii) to forecast areas for types of facilities not dealt with by the statistical analysis. The statistical forecast is based on fitting a regression model to the input data. The outcome of this work is presented in terms of three statistical relationships and an indirect relationship: between socio-economic and demographic variables (independent) to the dependent variables, either operating variables or land area variables, and between operating variables (independent) and land area variables (dependent), where for the latter there is also an indirect relationship while using standards.     

A causal inference approach to measure the vulnerability of urban metro systems

Transportation - Transit operators need vulnerability measures to understand the level of service degradation under disruptions. This paper contributes to the literature with a novel causal...     

Statistical modelling for ship propulsion efficiency

This paper presents a state-of-the-art systems approach to statistical modelling of fuel efficiency in ship propulsion, and also a novel and publicly available data set of high quality sensory data. Two statistical model approaches are investigated and compared: artificial neural networks and Gaussian processes (GP). The data presented is a publicly available full-scale data set, with a whole range of features sampled over a period of 2 months. We further discuss interpretations of the operational data in relation to the underlying physical system.