Urban dispersal events are processes where an unusually large number of people leave the same area in a short period. Early prediction of dispersal events is important in mitigating congestion and safety risks and making better dispatching decisions for taxi and ride-sharing fleets. Existing work mostly focuses on predicting taxi demand in the near future by learning patterns from historical data. However, they fail in case of abnormality because dispersal events with abnormally high demand are non-repetitive and violate common assumptions such as smoothness in demand change over time. Instead, in this paper we argue that dispersal events follow a complex pattern of trips and other related features in the past, which can be used to predict such events. Therefore, we formulate the dispersal event prediction problem as a survival analysis problem. We propose a two-stage framework (DILSA), where a deep learning model combined with survival analysis is developed to predict the probability of a dispersal event and its demand volume. We conduct extensive case studies and experiments on the NYC Yellow taxi dataset from 2014-2016. Results show that DILSA can predict events in the next 5 hours with F1-score of 0.7 and with average time error of 18 minutes. It is orders of magnitude better than the state-ofthe-art deep learning approaches for taxi demand prediction.
@cite_4: 
@cite_22: In big cities, taxi service is imbalanced. In some areas, passengers wait too long for a taxi, while in others, many taxis roam without passengers. Knowledge of where a taxi will become available can help us solve the taxi demand imbalance problem. In this paper, we employ a holistic approach to predict taxi demand at high spatial resolution. We showcase our techniques using two real-world data sets, yellow cabs and Uber trips in New York City, and perform an evaluation over 9,940 building blocks in Manhattan. Our approach consists of two key steps. First, we use entropy and the temporal correlation of human mobility to measure the demand uncertainty at the building block level. Second, to identify which predictive algorithm can approach the theoretical maximum predictability, we implement and compare three predictors: the Markov predictor (a probability-based predictive algorithm), the Lempel-Ziv-Welch predictor (a sequence-based predictive algorithm), and the Neural Network predictor (a predictive algorithm that uses machine learning). The results show that predictability varies by building block and, on average, the theoretical maximum predictability can be as high as 83 . The performance of the predictors also vary: the Neural Network predictor provides better accuracy for blocks with low predictability, and the Markov predictor provides better accuracy for blocks with high predictability. In blocks with high maximum predictability, the Markov predictor is able to predict the taxi demand with an 89 accuracy, 11 better than the Neural Network predictor, while requiring only 0.03 computation time. These findings indicate that the maximum predictability can be a good metric for selecting prediction algorithms.
@cite_7: Informed driving is increasingly becoming a key feature for increasing the sustainability of taxi companies. The sensors that are installed in each vehicle are providing new opportunities for automatically discovering knowledge, which, in return, delivers information for real-time decision making. Intelligent transportation systems for taxi dispatching and for finding time-saving routes are already exploring these sensing data. This paper introduces a novel methodology for predicting the spatial distribution of taxi-passengers for a short-term time horizon using streaming data. First, the information was aggregated into a histogram time series. Then, three time-series forecasting techniques were combined to originate a prediction. Experimental tests were conducted using the online data that are transmitted by 441 vehicles of a fleet running in the city of Porto, Portugal. The results demonstrated that the proposed framework can provide effective insight into the spatiotemporal distribution of taxi-passenger demand for a 30-min horizon.
@cite_8: 
@cite_15: Predicting taxi demand throughout a city can help to organize the taxi fleet and minimize the wait-time for passengers and drivers. In this paper, we propose a sequence learning model that can predict future taxi requests in each area of a city based on the recent demand and other relevant information. Remembering information from the past is critical here, since taxi requests in the future are correlated with information about actions that happened in the past. For example, someone who requests a taxi to a shopping center, may also request a taxi to return home after few hours. We use one of the best sequence learning methods, long short term memory that has a gating mechanism to store the relevant information for future use. We evaluate our method on a data set of taxi requests in New York City by dividing the city into small areas and predicting the demand in each area. We show that this approach outperforms other prediction methods, such as feed-forward neural networks. In addition, we show how adding other relevant information, such as weather, time, and drop-offs affects the results.
@cite_12: In this paper, we use time-series modeling to forecast taxi travel demand, in the context of a mobile application-based taxi hailing service. In particular, we model the passenger demand density at various locations in the city of Bengaluru, India. Using the data, we first shortlist time-series models that suit our application. We then analyse the performance of these models by using Mean Absolute Percentage Error (MAPE) as the performance metric. In order to improve the model performance, we employ a multi-level clustering technique where we aggregate demand over neighboring cells geohashes. We observe that the improved model based on clustering leads to a forecast accuracy of 80 per km2. In addition, our technique obtains an accuracy of 89 per km2 for the most frequently occurring use case.
@cite_17: The taxi is a flexible transportation system that everyone can move to any destination. However, in Japan, the charge for the taxi is more expensive than other transportation facilities. The taxi business is in a very tough situation because the cost of crude oil suddenly increased in addition to the influence of the oversupply of the taxi market. Recently, the application of Information Technologies has advanced on taxi industries (e.g., the fare payment by non-contact IC and car navigation system). One of the technologies that gain such the attention is a probe system which can store a large amount of customer trajectory data. The probe system will improve the profitability of taxi companies if the demand in the future can be forecasted from the statistics. Therefore, in this paper, we try to forecast the taxi demands from the taxi probe data by a neural network (i.e., multilayer perceptron). First, we analyze the statistics of the taxi demands and make the training data set for the neural network. Then, the back-propagation learning is applied to the neural network to reveal the relationship of regions in the Tokyo(i.e., 23-words, Mitaka-shi, and Musashino-shi). Finally, we report our discussion about the result.
has been studied closely in recent years, due to access to public taxi datasets @cite_22 . To the best of our knowledge none of the proposed methods directly address the prediction problem in case of anomaly. State-of-the-art methods for predicting taxi demand use historical data and time series analysis. @cite_4 propose a deep learning framework which captures the spatial and temporal dependencies to predict taxi demand. @cite_15 formulate an LSTM Network to learn the regular pattern of taxi demand. @cite_22 show the regular taxi demand is highly predictable and test different algorithms to approach the maximum accuracy. @cite_8 used spatial clustering to predict demand hotspots. They predict areas with high density of demand using DBSCAN. Such areas, despite having high demand, are part of the regular pattern. @cite_7 used streams of taxi data as time series to predict taxi demand in the next 30-minute period. @cite_12 used time series analysis to solve the demand prediction problem, giving recommendations to drivers. @cite_17 used a simple multi-output ANN to predict demand, using features created from recent demand, time and weather information.