Ying-En Ge

Comparing whole-link travel time models

In a model commonly used in dynamic traffic assignment the link travel time for a vehicle entering a link at time t is taken as a function of the number of vehicles on the link at time t. In an alternative recently introduced model, the travel time for a vehicle entering a link at time t is taken as a function of an estimate of the flow in the immediate neighbourhood of the vehicle, averaged over the time the vehicle is traversing the link. Here we compare the solutions obtained from these two models when applied to various inflow profiles. We also divide the link into segments, apply each model sequentially to the segments and again compare the results. As the number of segments is increased, the discretisation refined to the continuous limit, the solutions from the two models converge to the same solution, which is the solution of the Lighthill, Whitham, Richards (LWR) model for traffic flow. We illustrate the results for different travel time functions and patterns of inflows to the link. In the numerical examples the solutions from the second of the two models are closer to the limit solutions. We also show that the models converge even when the link segments are not homogeneous, and introduce a correction scheme in the second model to compensate for an approximation error, hence improving the approximation to the LWR model.

A new car-following model considering acceleration of lead vehicle

Abstract.For decades, the General Motors (GM) car following model has received a great deal of attention and provided a basic framework to describe the interactions between vehicles on the road. It is based on the stimulus-response assumption that the following vehicle responds to the relative speed between the lead vehicle and itself. However, some of the empirical findings show that the assumption of GM model is not always true and need some modification. For example, the acceleration of the following vehicle is very sensitive to the sign of the relative speed and because of no term in the model that directly represents the leaders acceleration, the followers response to the leaders acceleration can be retarded. This paper offers a new car-following model that can be considered as a variant of the GM model that can better capture car following behavior. The new model treats the followers acceleration as a proportion of a weighted sum of the leaders acceleration and the relative speed between the le...

Investigating undesired spatial and temporal boundary effects of congestion charging

Two types of reported problems are related to the existing congestion charging projects that levy traffic only in a certain area within one or a few time periods during the day. One is that travellers depart earlier or later than a charging period to avoid paying full or part of the congestion charging tolls, which creates two undesired demand peaks that are often greater than available capacity. One peak comes just before the start of congestion charging and the other follows the end of it. We term this phenomenon ‘temporal boundary effect’ of congestion charging. The other reported problem is that travellers would rather stay away from a charging zone than pay congestion charging tolls, which causes undesired congestion on those roads or paths on the edge of the charging zone. We call this phenomenon ‘spatial boundary effect’ generated by congestion charging. This research investigates these boundary effects in the context of simultaneous route and departure time choice dynamic user equilibrium (SRD-DUE) network flows with an aim to gain new insights into congestion charging design. Numerical experiments investigating constant and time-varying congestion charging toll profiles are presented in this paper. This investigation shows that congestion charging may not be able to eliminate hypercongestion efficiently if schemes are not well designed, and can unfortunately give rise to undesired boundary effects and that a simply designed congestion charging scheme with small level toll or time-varying toll profiles can reduce the magnitude of boundary effects but may not be able to fully eliminate such undesired effects.

Investigating boundary effects of congestion charging in a single bottleneck scenario

AbstractMany congestion charging projects charge traffic only within part of a day with predetermined congestion tolls. Demand peaks have been witnessed just around the time when the charge jumps up or down. Such peaks may not be desirable, in particular (a) when the resulting peaks are much higher than available capacities; (b) traffic speeding up to get into the charging zone causes more incidents just before the toll rises up to a higher level; or (c) traffic slowing down or parking on the roadside decreases road traffic throughput just before the toll falls sharply. We term these types of demand peaks ‘boundary effects’ of congestion charging. This paper investigates these effects in a bottleneck scenario and aims to design charging schemes that reduce undesired demand peaks. For this purpose, we observe and analyse the boundary effects utilising a bottleneck model under three types of toll profiles that are indicative of real charging schemes. The first type maintains a constant toll across the charg...

Investigating freeway traffic hypercongestion between an on-ramp and its immediate upstream off-ramp

This paper applies the freeway traffic congestion dynamics proposed in Laval and Leclercq [2010. “Continuum Approximation for Congestion Dynamics Along Freeway Corridors.” Transportation Science 44 (1): 87–97] but with a modified distribution scheme of freeway merging flows to investigation of traffic hypercongestion on a freeway between an on-ramp and its immediate upstream off-ramp. The reason to make this modification is that the original merging scheme of this dynamics is found to possibly give undesired full priority to the traffic from the on-ramp and also occasionally make the resulting flow going through the merge greater than the available capacity. Traffic hypercongestion in this paper refers to a state where speed and flow change in the same direction as density varies. A homogeneous freeway segment chosen for this investigation includes an on-ramp and an off-ramp, which may correspond to a freeway passing by a city or town, with an off-ramp lying upstream towards the city and an on-ramp downstream. The entry flow from the upstream approach of the freeway was fixed and constant within the time horizon while both deterministic and random on-ramp inflow rates were used in this investigation. Then the formation and dissipation of traffic hypercongestion is investigated as on-ramp demand and off-ramp departure profiles vary. The first finding of this investigation is that the density in the hypercongestion area behind the merge never reached the jam density. Second, the hypercongested area continued to grow as long as the sum of the demand from the upstream of the freeway and that from the on-ramp was greater than the available capacity at the merge. Third, as long as the rate of flow leaving from the freeway via the off-ramp was not smaller than the entry flow rates from the on-ramp, no hypercongestion had been observed. In addition, in analysing the numerical results, a series of discussions was carried out to build the linkage between the on- and off-ramp flow profiles and the generated and attracted demand of the city plus its adjacent area the two ramps served for; these discussions suggest that the balanced generated and attracted demand of the city plus its adjacent area can reduce or even remove traffic hypercongestion behind the merge on the chosen freeway segment.

Incorporating container location dispersion into evaluating GCR performance at a transhipment terminal

ABSTRACT The degree of container dispersion at a transhipment terminal is measured by an index termed container location dispersion, which represents the range, both horizontal and vertical, of all containers for ship loading that are scattered in the yard. First, this paper identifies the impacts of container location dispersion on loading performance with insufficient or sufficient equipment deployment in real-life settings at a terminal. Then, we investigate those scenarios with different levels of interference. This research aims to explore the relationship between the container location dispersion and Gross Crane Rate (GCR) stability at a transhipment terminal and proposes a discrete-event driven simulation model for this purpose. All data in our experiments are extracted from the terminal operation system at a real-life container terminal. It is concluded from a series of experiments that the container location dispersion well captures the overall performance of container terminal handling and can be used for yard template optimization and management. Implications of this investigation are discussed in the context of the yard template design and improvement in the overall performance of a container transhipment terminal.

Cost-Effective and Ecofriendly Plug-In Hybrid Electric Vehicle Charging Management

This study explored two charging management schemes for plug-in hybrid electric vehicles (PHEVs). The PHEV drivers and the government were stakeholders who might have preferred different charging control strategies. For the former, a proposed controlled charging scheme minimized the operational cost during PHEV charge-depleting and sustaining modes. For the latter, the research minimized monetized carbon dioxide emissions from electricity generation for the PHEVs charging, as well as tailpipe emissions for the portion of PHEV trips fueled by gasoline. Hourly driving patterns and electricity data were leveraged. Both were representative of each of the eight North American Electric Reliability Corporation regions to examine the results of the proposed schemes. The model accounted for drivers’ activity patterns and charging availability spatial and temporal heterogeneity. The optimal charging profiles confirmed the differing nature of the objectives of PHEV drivers and the government; cost-effective charge should occur early in the morning, while ecofriendly charge should be late in the afternoon. Each control’s trade-offs between operation cost and emission savings are discussed for each North American Electric Reliability Corporation region. The availability of workplace and public charging was found to affect the optimal charging profiles greatly. Charging control is more efficient for drivers and government when PHEVs have greater electric range.

Commentary on “A new generalized improved score function of interval-valued intuitionistic fuzzy sets and applications in expert systems” [Appl. Soft Comput., 2016(38) 988–999]

Abstract This commentary points out the major mistakes in “a new generalized improved score function of interval-valued intuitionistic fuzzy sets and applications in expert systems”, which were initially proposed by Garg [Appl. Soft Comput., 2016(38) 988–999]. Firstly, some related basic mathematical symbols are introduced. Secondly, Gargs research results are reviewed. Subsequently, the errors of the generalized weighted averaging operators and the restrictiveness of the generalized score function proposed by Garg are discussed by using four counter-cases. Thereafter, the sources that lead to the errors of the operators and the restrictiveness of the score function are revealed. Finally, this commentary also points out some typo-grammatical errors in the commented paper.

Could green taxation measures help incentivise future Chinese car drivers to purchase low emission vehicles

The paper begins with a brief review of evidence related to the different types of ‘green’ taxation measures that have been introduced by governments worldwide as a means to lessen the environmental consequences of private car ownership by incentivising the purchase of Low Emission Vehicles (LEVs). An overview is then provided of current understanding of individuals’ car purchasing decisions, highlighting gaps in knowledge that exist with current explanatory models. Based on these gaps in knowledge and to investigate the potential of various taxation measures in influencing individuals’ car purchasing decisions, an online survey was conducted with students from Dalian University of Technology, China. The questionnaire was designed to measure: (1) situational and psychological factors that would be important for their next car purchase; (2) the impacts of adapting current taxation measures to incentivise LEV purchases; (3) the potential role of a range of taxation measures on their decisions on type of future car purchases. K-Cluster means analysis was employed to identify population segments according to their psychological preparedness and importance attached to situational factors in their future decisions to purchase a LEV, or not. This resulted in three distinct segments – Pro-Greens (33.6% of sample), Maybe-Greens (20.2%) and No-Greens (46.2%). Pro-Greens were more psychologically prepared to purchase LEVs than the other two segments, whose future car purchasing decisions were primarily driven by situational factors (vehicle characteristics, performance, etc.). Pro-Greens were also more likely to be influenced by changes in current Chinese taxation measures (VAT and fuel duty), and also significantly more likely to be influenced by the introduction of future measures that would incentivise LEV purchases than the other two segments. In terms of future measures to incentivise future Chinese drivers LEV purchases and use, the introduction of a feebate system, a CO2 emissions VAT system, a distance based user charging scheme and annual road tax based on CO2 emissions would appear to have the greatest potential overall.

The environmental costs and economic implications of container shipping on the Northern Sea Route

ABSTRACT The Northern Sea Route (NSR) has tremendous potential for ocean shipping between Europe and Asia due to the savings from shorter transit time and distance. However, the Arctic area is environmentally vulnerable and thus there is a trade-off between NSR’s impacts on environment vs. its economic benefits, especially when compared with the traditional route, such as through the Suez Canal Route (SCR). This study estimates the market shares of different transport modes and alternative shipping routes for the container transport market between Europe and Asia, and the resulting environmental costs. Our result suggests that NSR can be a viable option under the status quo. However, its environmental costs tend to be higher than SCR due to small ship size and low load factor in the present, thus the development of NSR would lead to worse environment outcomes. If these issues can be resolved, NSR can benefit from lower operational and environmental costs, which will lead to higher market share and social welfare. Otherwise, increased use of NSR may lead to higher total environment costs than the status quo.