Dockless bike-sharing systems: what are the implications?

ABSTRACT

The emergence of dockless bike-sharing services has revolutionised bike-sharing markets in recent years, and the dramatic growth of shared bike fleets in China, as well as their rapid expansion throughout the world, exceeds prior expectations. An understanding of the impacts of these new dockless bike-sharing systems is of vital importance for system operations, transportation and urban planning research. This paper provides a first overview of the emerging literature on implications of dockless bike-sharing systems for users' travel behaviour, user experience, and relevant social impacts of dockless bike-sharing systems. Our review suggests that the dockless design of bike-sharing systems significantly improves users' experiences at the end of their bike trips. Individuals can instantly switch to a dockless shared bike without the responsibility of returning it back to a designated dock. Additionally, the high flexibility and efficiency of dockless bike-sharing often makes the bike-sharing systems' integration with public transit even tighter than that of traditional public bikes, providing an efficient option for first/last-mile trips. The GPS tracking device embedded in each dockless shared bike enables the unprecedented collection of large-scale riding trajectory data, which allow scholars to analyse people's travel behaviour in new ways. Although many studies have investigated travel satisfaction amongst cyclists, there is a lack of knowledge of the satisfaction with bikeshare trips, including both station-based and dockless bikeshare systems. The availability and usage rates of dockless bike-sharing systems implies that they may seriously impact on individuals' subjective well-being by influencing their satisfaction with their travel experiences, health and social participation, which requires further exploration. The impact of dockless bike-sharing on users' access to services and social activities and the related decreases in social exclusion are also relevant issues about which knowledge is lacking. With the increases in popularity of dockless shared bikes in some cities, issues related to the equity and access and the implications for social exclusion and inequality are also raised.     

THE LA ANTIGEN INHIBITS THE ACTIVATION OF THE INTERFERON－INDUCIBLE PROTEIN KINASE PKR BY SEQUESTERING AND UNWINDING DOUBLE－ST

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Preview-Based Control of Suspension Systems for Commercial Vehicles

An active suspension with preview is developed for the rear axle of a commercial vehicle. The obtained improvements are promising and justify further investigation of the more feasible semi-active suspensions with preview. The inherent non-linearity of semi-active suspensions with switching shock absorbers and the need for controllers that can handle a broad class of control objectives has led to the development of several numerical control methods for both multi-level and continuously variable shock absorbers. The most promising control method and shock absorber type are selected and mounted in a test vehicle. Some first experimental results are discussed.     

Elderly travel frequencies and transport mode choices in Greater Rotterdam,the Netherlands

Demographic ageing is a key societal challenge in Europe as well as in many other western and non-western societies. A crucial dimension concerns elderly daily mobility patterns. While still partaking fewer and shorter trips than younger generations, today’s elderly have been found increasingly (auto)mobile. Although the elderly benefit from the independence, freedom of movement, and social inclusion, concerns may rise regarding the environmental and accessibility impacts of this induced mobility. The present study adds to the expanding literature on elderly mobility, an integrated analysis of the effects of socio-demographic, health, trip, spatial and weather attributes on elderly mobility. Utilizing travel diary data for Greater Rotterdam, The Netherlands, trip frequencies and transport mode choices of the elderly are analysed by means of zero-inflated negative binomial models as well as multinomial logit regression models, and contrasted to the non-elderly subpopulation to explore (dis)similarities. While the results show common determinants, the models also highlight important differences in the magnitude of the estimated coefficients and factors only influencing transport patterns for the elderly. Embedded in the context of an aging population, the empirical findings assist policy-makers and planners in several respects: For transportation plans and programs it is critical to recognize mobility needs of the elderly. As the seniors are becoming increasingly automobile, the results call for strategies to encourage older people to use more physically active and environmentally friendly transport modes such as public transport, walking and cycling.     

Involvement in clubs or voluntary associations, social networks and activity generation: a path analysis

Leisure activities have received increasing attention from travel behavior researchers over the past decade. However, these activities are often treated as a single category, neglecting their differences. Whereas most leisure activities are flexible, club activities are usually scheduled longer in advance and are more fixed in time, location and company. Hence, trip-generating properties of club activities are likely to differ from those of other leisure activities. As very little is known about involvement in clubs or voluntary associations in relation to trip generation, voluntary association activities deserve further research in relation to travel. Therefore, in this paper a path analysis is conducted, analyzing the relationships between participation in clubs or voluntary associations, trip frequencies, and social network characteristics. The analyses are based on data collected in 2011 in Eindhoven in the Netherlands in a survey among 516 respondents. The results show interesting relationships between the social context and involvement in clubs. They indicate that people become club members through their social networks, and frequent club activities increase social network size. Family oriented people were found to go less often to clubs. Club membership and the frequency of going to club activities were also found to be affected by socio-demographics, such as gender, age, education, work, presence of young children in the household and owning a season ticket for public transport.     

Time series for sea water and seaweed of Tc and Sb originating from releases at La Hague

⁹⁹Tc and ¹²⁵Sb have been released in low level liquid waste at the reprocessing plant at La Hague (Fr). Over a number of years data have been obtained on the concentration of ⁹⁹Tc in sea water and in seaweed from sampling locations close to and at increasing distances north and east of the point of release into the English Channel.In addition such data have been obtained on ¹²⁵Sb for a small number of sampling points. These time series, and the information derived from their intercomparison and from comparison with the release data, are presented in this paper.Time series on ⁹⁹Tc as well as ¹²⁵Sb in sea water and seaweed clearly confirm a considerable decrease in release rates at La Hague over the years 1986–1993. Transit times and transfer factors derived from the series are generally in good agreement with the results of modelling efforts. The data do not provide evidence for a time lag between levels of the radionuclides in sea water and those in seaweed longer than a few months.The very high concentration factors for ⁹⁹Tc in brown seaweeds make these seaweeds very useful for environmental monitoring the radionuclide at low release rates and to trace releases in areas remote from the point of release.     

Consistent link flow estimation from counts

Partly because of counting errors and partly because counts may be carried out on different days, traffic counts on links of a network are unlikely to satisfy the flow conservation constraint “flow IN = flow out” at every node of the network. Van Zuylen and Willumsen (1980) have described a method of eliminating inconsistencies in traffic counts when a single count is available for each link in the network. In this paper, the method is extended to the case when more than one count is available on some links of the network. In addition, an algorithm is described for application of the method.     

驾驶模拟在公路安全设计与运行中运用的研究

随着日益增长的交通需求,为了能够获得最高性能的公路交通系统,驾驶任务变得越来越复杂,公路设计和建设中考虑人的因素也变得更为重要.能否成功引进新的驾驶支持体系、动态的交通管理系统或者复杂的道路设计,主要依赖于人们是否能够以及有多大意愿去适应这种发展.为此需要了解人们在复杂的动态驾驶任务环境中将会做出怎样的反应.该文在简单地介绍完TNO驾驶模拟器设备后,又介绍了有关利用先进的人机互动驾驶模拟器研究人的驾驶行为来进行公路设计和建设.文中通过几个公路设计和交通运输行为研究的例子,说明了驾驶模拟器研究对安全有效地进行公路设计与运行运用具有特殊的价值.     

The effect of resuspension on chemical exchanges at the sediment-water interface in the deep sea — A modelling and natural radiotracer approach

We review the processes responsible for the formation of vertical gradients in the chemical composition of suspended particles across the benthic nepheloid layer. Such gradients have usually explained by resuspension of surface sediments, but it is shown here that these gradients can only be understood as part of a dynamic exchange between the water column and the sediments. A coupled model, developed in a companion paper, is expanded to include chemical reactions above and below the sediment-water interface. Three cases are discussed: A tracer with first-order decay (Model 1), the dissolution of a major constituent (Model 2), and a particle-reactive tracer with first-order decay and production in the water column (Model 3). Using typical parameter values for a well-developed benthic nepheloid layer, the three models reproduce typical distributions of C_org (organic carbon), opal, and ²³⁴Th, respectively, on particles above and below the sediment-water interface. Sensitivity analyses illustrate how bioturbation can cause the large discrepancy observed between suspended and surface sediment C_org values (Model 1). The model also reconciles this observed discrepancy with observations that the major part of the decomposition takes place within the sediment. For opal (Model 2), the influence of resuspension on the burial rate of opal is shown to be negligible, as long as dissolution follows first-order kinetics and is not enhanced by turbulence in the suspended phase. The modelling of ²³⁴Th (Model 3) successfully links the depletion of ²³⁴Th in bottom waters with the distribution of excess ²³⁴Th in surface sediments and on resuspended particles.²³⁴Th is a powerful example of the tools supplied by the radioactive daughters of the natural U and Th decay series in studying fluxes and exchange rates of solutes and particles across the sediment-water interface. A short review is given of these tools, and it is shown how they can be used to obtain rate information required to apply and calibrate specific resuspension models.