Congestion behavior and tolls in a bottleneck model with stochastic capacity

In this paper we investigate a bottleneck model in which the capacity of the bottleneck is assumed stochastic and follows a uniform distribution. The commuters’ departure time choice is assumed to follow the user equilibrium principle according to mean trip cost. The analytical solution of the proposed model is derived. Both the analytical and numerical results show that the capacity variability would indeed change the commuters’ travel behavior by increasing the mean trip cost and lengthening the peak period. We then design congestion pricing schemes within the framework of the new stochastic bottleneck model, for both a time-varying toll and a single-step coarse toll, and prove that the proposed piecewise time-varying toll can effectively cut down, and even eliminate, the queues behind the bottleneck. We also find that the single-step coarse toll could either advance or postpone the earliest departure time. Furthermore, the numerical results show that the proposed pricing schemes can indeed improve the efficiency of the stochastic bottleneck through decreasing the system’s total travel cost

Modeling Airline Frequency Competition for Airport Congestion Mitigation

Demand often exceeds capacity at congested airports. Airline frequency competition is partially responsible for the growing demand for airport resources. We propose a game-theoretic model for airline frequency competition under slot constraints. The model is solved to obtain a Nash equilibrium using a successive optimizations approach, wherein individual optimizations are performed using a dynamic programming-based technique. The model predictions are validated against actual frequency data, with the results indicating a close fit to reality. We use the model to evaluate different strategic slot allocation schemes from the perspectives of the airlines and the passengers. The most significant result of this research shows that a small reduction in the total number of allocated slots translates into a substantial reduction in flight and passenger delays and also a considerable improvement in airlines' profits

Tradable credit scheme for rush hour travel choice with heterogeneous commuters

This article proposes a tradable credit scheme for managing commuters travel choices. The scheme considers bottleneck congestion and modal split in a competitive highway-transit network with heterogeneous commuters who are distinguished by their valuation of travel time. The scheme charges all auto travelers who pass the bottleneck during a peak-time window in the form of mobility credits. Those who avoid the peak-time window, by either traveling outside the peak-time window or switching to the transit mode, may be rewarded credits. An artificial market is created so that the travelers may trade these credits with each other. We formulate the credit price and the rewarded and charged credits under tradable credit scheme. Our analyses indicate that the optimal tradable credit scheme can achieve nearly 40% efficiency gains depending on the level of commuters heterogeneity. In addition, this scheme distributes the benefits among all the commuters directly through the credit trading. Our results suggest that in assessing the efficiency of tradable credit scheme, it is important to take into account the commuters heterogeneity. Numerical experiments are conducted to examine the sensitivity of tradable credit scheme designs to various system parameters

Transient activation of dopaminergic neurons during development modulates visual responsiveness, locomotion and brain activity in a dopamine ontogeny model of schizophrenia

It has been observed that certain developmental environmental risk factors for schizophrenia when modeled in rodents alter the trajectory of dopaminergic development, leading to persistent behavioural changes in adults. This has recently been articulated as the "dopamine ontogeny hypothesis of schizophrenia". To test one aspect of this hypothesis, namely that transient dopaminergic effects during development modulate attention-like behavior and arousal in adults, we turned to a small-brain model, Drosophila melanogaster. By applying genetic tools allowing transient activation or silencing of dopaminergic neurons in the fly brain, we investigated whether a critical window exists during development when altered dopamine (DA) activity levels could lead to impairments in arousal states in adult animals. We found that increased activity in dopaminergic neurons in later stages of development significantly increased visual responsiveness and locomotion, especially in adult males. This misallocation of visual salience and hyperactivity mimicked the effect of acute methamphetamine feeding to adult flies, suggesting up-regulated DA signaling could result from developmental manipulations. Finally, brain recordings revealed significantly reduced gamma-band activity in adult animals exposed to the transient developmental insult. Together, these data support the idea that transient alterations in DA signaling during development can permanently alter behavior in adults, and that a reductionist model such as Drosophila can be used to investigate potential mechanisms underlying complex cognitive disorders such as schizophrenia

Reduction in Local Ozone Levels in Urban São Paulo Due to a Shift from Ethanol to Gasoline Use

It has been proposed that lower NOx emission fuels such as ethanol can mitigate air pollution from vehicles burning oil-based hydrocarbons. Yet, existing modeling and laboratory studies, even those seeking to simulate the same environment, vary in their predictions of how gasoline/ethanol blends affect atmospheric pollutant concentrations, including ozone. Importantly, ambient concentrations have not been evaluated during an actual – as opposed to hypothetical – shift in fuel mix in a real-world environment. Here, we report the first such study, for the subtropical megacity of São Paulo, Brazil. We combine detailed street-hour level data on regulated pollutant concentrations, meteorology, and traffic with fuel shares from a consumer demand model to compare concentrations across subsamples that differ only in the fuel mix but are otherwise similar in meteorology, anthropogenic activity, and biogenic emissions. As the gasoline share of the bi-fuel light-duty vehicle fleet rose by 62 percentage points, we estimate a robust and statistically significant reduction of about 20% in ozone concentrations, and less precise increases in NO and CO concentrations. We propose that our “model-free” analysis potentially accounts for the interaction between anthropogenic and biogenic emissions and caution that successful strategies against ozone pollution require knowledge of the local chemistry and analysis beyond the presently monitored pollutants, most notably fine particles