Estimated time of arrival (ETA) is one of the most important services in intelligent transportation systems (ITS). Precise ETA ensures proper travel scheduling of passengers as well as guarantees efficient decision-making on ride-hailing platforms, which are used by an explosively growing number of people in the past few years. Recently, machine learning-based methods have been widely adopted to solve this time estimation problem and become state-of-the-art. However, they do not well explore the personalization information, as many drivers are short of personalized data and do not have sufficient trajectory data in real applications. This data sparsity problem prevents existing methods from obtaining higher prediction accuracy. In this article, we propose a novel deep learning method to solve this problem. We introduce an auxiliary task to learn an embedding of the personalized driving information under multi-task learning framework. In this task, we discriminatively learn the embedding of driving preference that preserves the historical statistics of driving speed. For this purpose, we adapt the triplet network from face recognition to learn the embedding by constructing triplets in the feature space. This simultaneously learned embedding can effectively boost the prediction accuracy of the travel time. We evaluate our method on two large-scale real-world datasets from Didi Chuxing platform. The extensive experimental results on billions of historical vehicle travel data demonstrate that the proposed method outperforms state-of-the-art algorithms.

With millions of people using ride-hailing platforms for daily travel, estimated time of arrival (ETA) has become a significant problem in intelligent transportation systems and attracted considerable attention recently. Deep learning-based ETA methods have achieved promising results using massive spatial-temporal data. However, we find that the prediction accuracy is not satisfactory in practical applications due to the prevalent data sparsity problems. Instead of focusing on the average prediction performance as many other methods, this study aims to alleviate the data sparsity problems in ETA to enhance user experience. In general, the data sparsity problems arise from two aspects. The first is the road network, where many links are only traversed by few floating cars. The second aspect is drivers, where many drivers’ trajectories are too scarce (e.g., with only 3 trip records). To alleviate the sparsity in road network, we propose a Road Network Metric Learning framework for ETA (RNML-ETA), where an auxiliary metric learning task is used to improve the link-embedding, especially for links with insufficient data. A novel triangle loss is proposed to improve metric learning effectiveness for links. Experiments on massive real-world data show that RNML-ETA outperforms competing methods by promoting the cold links with limited data. Furthermore, we propose a novel unified framework to Alleviate Data Sparsity problems in ETA (ADS-ETA) by extending RNML-ETA with an additional auxiliary task for driver ID embedding. Results with extensive experiments demonstrate that ADS-ETA can effectively alleviate the data sparsity problems caused by road network and driver sparsity.

Estimated time of arrival (ETA) is one of the most important services in intelligent transportation systems (ITS) and becomes a challenging spatial-temporal (ST) data mining task in recent years. Nowadays, deep learning based methods, specifically recurrent neural networks (RNN) based ones are adapted to model the ST patterns from massive data for ETA and become the state-of-the-art. However, RNN is suffering from slow training and inference speed, as its structure is unfriendly to parallel computing. To solve this problem, we propose a novel, brief and effective framework mainly based on feed-forward network (FFN) for ETA, FFN with Multifactor Attention (FMA-ETA). The novel Multi-factor Attention mechanism is proposed to deal with different category features and aggregate the information purposefully. Extensive experimental results on the real-world vehicle travel dataset show FMA-ETA is competitive with state-of-the-art methods in terms of the prediction accuracy with significantly better inference speed.

Multi-horizon time series forecasting plays an important role in many industrial and business decision processes. To grasp complex and various patterns across different time series is the crucial step in achieving promising performance. However, most deep learning-based forecasting approaches simply take series-specific static (i.e. time-invariant) covariates as input features, which can fail to capture the complex pattern variation for each possible time series. In this paper, we propose a novel multiplicative attention-based architecture to tackle such forecasting problem. Our modification to multi-head attention layers leverages the series-specific covariates to build flexible attention functions for each possible time series. This improvement contributes to greater representation capacity to grasp different patterns across related time series. Experiment results demonstrate that our approach achieves state-of-the-art performance on a variety of real-world datasets.

Deep convolutional neural networks have achieved great success in many computer vision tasks. However, they can be attacked by adversarial examples which are input-data with small intentional feature perturbations to fool machine learning models. This vulnerability to adversarial examples poses a potential threat to their widespread application, especially in security-sensitive scenarios. In this paper, we revisit adversarial examples in the frequency domain referring to the computational theory of edge detection, and propose a noveldensely high-frequency convolution neural network(DiFNet) to effectively defend against adversarial attacks. DiFNet introduces classical edge detection operations into the network structure to enhance the detection ability for high-frequency components in the image. It works well to defend against the imperceptible perturbations attacks even without adversarial examples. Experiments demonstrate that DiFNet outperforms handcraft-designed CNNs in terms of prediction accuracy with improved robustness against state-of-the-art adversarial attacks (FGSM, PGD, etc.).

Recently, deep learning have achieved promising results in Estimated Time of Arrival (ETA), which is considered as predicting the travel time from the origin to the destination along a given path. One of the key techniques is to use embedding vectors to represent the elements of road network, such as the links (road segments). However, the embedding suffers from the data sparsity problem that many links in the road network are traversed by too few floating cars even in large ride-hailing platforms like Uber and DiDi. Insufficient data makes the embedding vectors in an under-fitting status, which undermines the accuracy of ETA prediction. To address the data sparsity problem, we propose the Road Network Metric Learning framework for ETA (RNML-ETA). It consists of two components: (1) a main regression task to predict the travel time, and (2) an auxiliary metric learning task to improve the quality of link embedding vectors. We further propose the triangle loss, a novel loss function to improve the efficiency of metric learning. We validated the effectiveness of RNML-ETA on large scale realworld datasets, by showing that our method outperforms the state-of-the-art model and the promotion concentrates on the cold links with few data.

Traffic forecasting influences various intelligent transportation system (ITS) services and is of great significance for user experience as well as urban traffic control. It is challenging due to the fact that the road network contains complex and time-varying spatial-temporal dependencies. Recently, deep learning based methods have achieved promising results by adopting graph convolutional network (GCN) to extract the spatial correlations and recurrent neural network (RNN) to capture the temporal dependencies. However, the existing methods often construct the graph only based on road network connectivity, which limits the interaction between roads. In this work, we propose Geographic and Long-term Temporal Graph Convolutional Recurrent Neural Network (GLT-GCRNN), a novel framework for traffic forecasting that learns the rich interactions between roads sharing similar geographic or longterm temporal patterns. Extensive experiments on a real-world traffic state dataset validate the effectiveness of our method by showing that GLT-GCRNN outperforms the state-of-the-art methods in terms of different metrics.

Computing estimated time of arrival (ETA) is one of the most important services for online ride-hailing platforms like DiDi and Uber. With billions of service queries per day on such platforms, a fast inference ETA module ensures the efficiency of the overall decision system to guarantee satisfied user experience, as well as saving significant operating cost. In this paper, we develop a novel ETA learning system named as CompactETA, which provides an accurate online travel time inference within 100 microseconds. In the proposed method, we encode high order spatial and temporal dependency into sophisticated representations by applying graph attention network on a spatiotemporal weighted road network graph. We further encode the sequential information of the travel route by positional encoding to avoid the recurrent network structure. The properly learnt representations enable us to apply a very simple multi-layer perceptron model for online real-time inference. Evaluation of both offline experiments and online A/B testing verifies that CompactETA reduces the inference latency by more than 100 times compared to a state-of-the-art system, while maintains competing prediction accuracy.

The estimated time of arrival (ETA) is a critical task in the intelligent transportation system, which involves the spatiotemporal data. Despite a significant amount of prior efforts have been made to design efficient and accurate systems for ETA task, few of them take structural graph data into account, much less the heterogeneous information network. In this paper, we propose HetETA to leverage heterogeneous information graph in ETA task. Specifically, we translate the road map into a multi-relational network and introduce a vehicle-trajectories based network to jointly consider the traffic behavior pattern. Moreover, we employ three components to model temporal information from recent periods, daily periods and weekly periods respectively. Each component comprises temporal convolutions and graph convolutions to learn representations of the spatiotemporal heterogeneous information for ETA task. Experiments on large-scale datasets illustrate the effectiveness of the proposed HetETA beyond the state-of-the-art methods, and show the importance of representation learning of heterogeneous information networks for ETA task.

The dramatic development of shared mobility in food delivery, ridesharing, and crowdsourced parcel delivery has drawn great concerns. Specifically, shared mobility refers to transferring or delivering more than one passenger/package together when their traveling routes have common sub-routes or can be shared. A core problem for shared mobility is to plan a route for each driver to fulfill the requests arriving dynamically with given objectives. Previous studies greedily and incrementally insert each newly coming request to the most suitable worker with a minimum travel cost increase, which only considers the current situation and thus not optimal. In this paper, we propose a demand-aware route planning (DARP) for shared mobility services. Based on prediction, DARP tends to make optimal route planning with more information about requests in the future. We prove that the DARP problem is NP-hard, and further show that there is no polynomial-time deterministic algorithm with a constant competitive ratio for the DARP problem unless P=NP. Hence, we devise an approximation algorithm to realize the insertion operation for our goal. With the insertion algorithm, we devise a prediction based solution for the DARP problem. Extensive experiment results on real datasets validate the effectiveness and efficiency of our technique.

With the rapid development of smart mobile devices, the car-hailing platforms (e.g., Uber or Lyft) have attracted much attention from both the academia and the industry. In this paper, we consider an important dynamic car-hailing problem, namely maximum revenue vehicle dispatching (MRVD), in which rider requests dynamically arrive and drivers need to serve as many riders as possible such that the entire revenue of the platform is maximized. We prove that the MRVD problem is NP-hard and intractable. To handle the MRVD problem, we propose a queueing-based vehicle dispatching framework, which first uses existing machine learning algorithms to predict the future vehicle demand of each region, then estimates the idle time periods of drivers through a queueing model for each region. With the information of the predicted vehicle demands and estimated idle time periods of drivers, we propose one batch-based vehicle dispatching algorithm to efficiently assign suitable drivers to riders such that the expected entire revenue of the platform is maximized during each batch processing. Through experiments over real data sets, we demonstrate the efficiency and effectiveness of our proposed framework.

One crucial task in intelligent transportation systems is estimating the duration of a potential trip given the origin location, destination location as well as the departure time. Most existing approaches for travel time estimation assume that the route of the trip is given, which does not hold in real-world applications since the route can be dynamically changed due to traffic conditions, user preferences, etc. As inferring the path from the origin and the destination can be time-consuming and nevertheless error-prone, it is desirable to perform origin-destination travel time estimation, which aims to predict the travel time without online route information. This problem is challenging mainly due to its limited amount of information available and the complicated spatiotemporal dependency. In this paper, we propose a MUlti-task Representation learning model for Arrival Time estimation (MURAT). This model produces meaningful representation that preserves various trip properties in the real-world and at the same time leverages the underlying road network and the spatiotemporal prior knowledge. Further-more, we propose a multi-task learning framework to utilize the path information of historical trips during the training phase which boosts the performance. Experimental results on two large-scale real-world datasets show that the proposed approach achieves clear improvements over state-of-the-art methods

Vehicle travel time estimation or estimated time of arrival (ETA) is one of the most important location-based services (LBS). It is becoming increasingly important and has been widely used as a basic service in navigation systems and intelligent transportation systems. This paper presents a novel machine learning solution to predict the vehicle travel time based on floating-car data. First, we formulate ETA as a pure spatial-temporal regression problem based on a large set of effective features. Second, we adapt different existing machine learning models to solve the regression problem. Furthermore, we propose a Wide-Deep-Recurrent (WDR) learning model to accurately predict the travel time along a given route at a given departure time. We then jointly train wide linear models, deep neural networks and recurrent neural networks together to take full advantages of all three models. We evaluate our solution offline with millions of historical vehicle travel data. We also deploy the proposed solution on Didi Chuxing's platform, which services billions of ETA requests and benefits millions of customers per day. Our extensive evaluations show that our proposed deep learning algorithm significantly outperforms the state-of-the-art learning algorithms, as well as the solutions provided by leading industry LBS providers.

In this paper, we present a homotopy regularization algorithm for boosting. We introduce a regularization term with adaptive weight into the boosting framework and compose a homotopy objective function. Optimization of this objective approximately composes a solution path for the regularized boosting. Following this path, we can find suitable solution efficiently using early stopping. Experiments show that this adaptive regularization method gives a more efficient parameter selection strategy than regularized boosting and semi supervised boosting algorithms, and significantly improves the performances of traditional AdaBoost and related methods.

This paper presents an active learning strategy for boosting. In this strategy, we construct a novel objective function to unify semi-supervised learning and active learning boosting. Minimization of this objective is achieved through alternating optimization with respect to the classifier ensemble and the queried data set iteratively. Previous semi-supervised learning or active learning methods based on boosting can be viewed as special cases under this framework. More important, we derive an efficient active learning algorithm under this framework, based on a novel query mechanism called query by incremental committee. It does not only save considerable computational cost, but also outperforms conventional active learning methods based on boosting. We report the experimental results on both boosting benchmarks and real-world database, which show the efficiency of our algorithm and verify our theoretical analysis.