Life duration of bike sharing systems

Many factors have been advanced to predicate the sustainability of bike sharing system (BSS) and bike sharing usage, such as fleet size, number of docking stations, payment type and financial support, but there have been few studies that examine survival duration of BSS’ operation. Therefore, this study investigates the determinants of BSS’ duration, using bike sharing monitoring map and respective annual report data from 106 cities around the world. Three categories of independent variables, namely infrastructural factors, social factors and economic factors are included in the generalised linear model (GLM). The findings indicate that coverage area, system capacity and payment type will affect the sustainability of bike sharing operation. Moreover, financial support and purchasing power parity (PPP) per capital are the distinctive factors that seem to influence the likelihood of success of a BSS. Payment method affects the survivability of a BSS after the system is stable

COOR-PLT: A hierarchical control model for coordinating adaptive platoons of connected and autonomous vehicles at signal-free intersections based on deep reinforcement learning

Platooning and coordination are two implementation strategies that are frequently proposed for traffic control of connected and autonomous vehicles (CAVs) at signal-free intersections instead of using conventional traffic signals. However, few studies have attempted to integrate both strategies to better facilitate the CAV control at signal-free intersections. To this end, this study proposes a hierarchical control model, named COOR-PLT, to coordinate adaptive CAV platoons at a signal-free intersection based on deep reinforcement learning (DRL). COOR-PLT has a two-layer framework. The first layer uses a centralized control strategy to form adaptive platoons. The optimal size of each platoon is determined by considering multiple objectives (i.e., efficiency, fairness and energy saving). The second layer employs a decentralized control strategy to coordinate multiple platoons passing through the intersection. Each platoon is labeled with coordinated status or independent status, upon which its passing priority is determined. As an efficient DRL algorithm, Deep Q-network (DQN) is adopted to determine platoon sizes and passing priorities respectively in the two layers. The model is validated and examined on the simulator Simulation of Urban Mobility (SUMO). The simulation results demonstrate that the model is able to: (1) achieve satisfactory convergence performances; (2) adaptively determine platoon size in response to varying traffic conditions; and (3) completely avoid deadlocks at the intersection. By comparison with other control methods, the model manifests its superiority of adopting adaptive platooning and DRL-based coordination strategies. Also, the model outperforms several state-of-the-art methods on reducing travel time and fuel consumption in different traffic conditions.Comment: This paper has been submitted to Transportation Research Part C: Emerging Technologies and is currently under revie

Social Thinking and Risk Between Road Users: The Case of the Pedestrian in Two Cultural Contexts

Interactions between motorized and non-motorized road users constitute situations of risk for the latter. Improving the safety of pedestrians, who are the most vulnerable users, is a challenge for public health in society. The aims of this study concern the social representation of the pedestrian and the impact of the cultural variable in the construction of this knowledge; a field in which there exists little research. In this perspective, the discourse of two groups of students, one from a French city (N=85) and one from Singapore (N=124) are compared. The use of free associations and specific analyses makes it possible to isolate the words or expressions most frequently associated with pedestrians and those that discriminate the two populations. This study reveals that the pedestrian is associated with risk in both cultural environments. Nevertheless the French express more fear and apprehension and the Singaporeans’ representation is both more descriptive and personified. These results are discussed in relation to the cultural contexts

Dynamic interactions between commuter's mode choice behaviour and integrated traveller information

A commuter’s mode choice decision in response to provided traveller information is directly dependent on the temporal and spatial interactions between the available travel modes, the network performance and control schemes, and the supplied traveller information. A self-developed simulation model – Intelligent Network Simulation Model (INSIM) – was employed to simulate travel scenarios in a multimodal transportation network. A set of experiments was designed to analyse and evaluate the influence of traffic information on commuter’s mode choice, using a medium-sized area in Singapore. Simulation results showed that the private-to-public mode switch propensity bears a strong and direct relation with amount of disseminated integrated multimodal traveller information (IMTI) as well as timeliness of information update. Other influential factors include degrees of accessibility and compliance to IMTI, and congestion-related events such as accidents

Impact of traveller information on mode choice behaviour

This paper analysed automobile commuters' mode choice behaviour under the influence of simulated multimodal traveller information by developing two logit models. A combined revealed preference (RP)/stated preference (SP) travel behaviour survey was administered to drivers to gather individual commuters' travel decisions under integrated multimodal traveller information. Two SP scenarios were designed where the first scenario is to test the mode choice preference in a basic situation involving a congested work/school trip with information on several travel options, and the second scenario is to investigate the mode choice decision when certain incentives are given for public transport. Results showed that integrated multimodal traveller information can influence a traveller's mode choice decision. The influencing factors that significantly affect the mode choice decision include socio-economic characteristics – for example, gender, age, level of education and level of income – and multimodal traveller information attributes – for example, access mode to mass rapid transit (MRT) station, access time to MRT station and transit seat availability. The findings are useful to traffic management agencies for designing better operational policy and information publication strategies

Feasibility study of bike sharing in Singapore

This study analysed the feasibility of a bike-sharing programme in Singapore based on a case study in the Jurong Lake district. Data were collected using a two-stage perception survey to gather the public’s general awareness and opinions about bike sharing and followed by estimating the likely take-up rate of bike sharing. The results showed that bike-sharing schemes would be suitable around mass rapid transit stations and low rental costs would encourage bike sharing. Finally, a distance-based mode-choice model was established for four scenarios (morning peak and good weather, morning peak and bad weather, evening peak and good weather and evening peak and bad weather), focusing on walking, bike sharing and taking a bus. Weather could have an obvious impact on the frequency of bike sharing

Driver behaviour at horizontal curves

Studies relating accident occurrence to horizontal curve geometry indicate a strong association between the radius of horizontal curves and accident occurrence, but the individual effect of horizontal curvature on safety is still uncertain. The preponderance of human error as a contributory cause of accidents has led to a growing interest in research on driver behaviour. The human factor in road safety is discussed and literature on driver behaviour on horizontal curves is reviewed. A study involving unobtrusive observation of driver behaviour at two curves (an isolated curve and a reverse curve) before and after realignment was carried out. Data on driver behaviour was collected by continuous video-recording of each subject vehicle as it moved through each curve. Lateral placement and speed data along the curve were extracted from the video record, and the path radius and sideway force coefficient at the mid-point of the curve were estimated. The observed driver behaviour is discussed. The results of the study were checked against the underlying design assumptions, which are shown not to be completely and universally valid. The evaluation of the realignment, based on driver behaviour and the sideway force coefficient, and the accident records show that there was an overall improvement in the margin of safety at all the curves (except one). The results do not support the concept of risk homeostasis, although there is evidence of risk compensation