Predicting vehicle trajectories is crucial to ensuring automated vehicle operation efficiency and safety, particularly on congested multi-lane highways. In such dynamic environments, a vehicle's motion is determined by its historical behaviors as well as interactions with surrounding vehicles. These intricate interactions arise from unpredictable motion patterns, leading to a wide range of driving behaviors that warrant in-depth investigation. This study presents the Graph-based Interaction-aware Multi-modal Trajectory Prediction (GIMTP) framework, designed to probabilistically predict future vehicle trajectories by effectively capturing these interactions. Within this framework, vehicles' motions are conceptualized as nodes in a time-varying graph, and the traffic interactions are represented by a dynamic adjacency matrix. To holistically capture both spatial and temporal dependencies embedded in this dynamic adjacency matrix, the methodology incorporates the Diffusion Graph Convolutional Network (DGCN), thereby providing a graph embedding of both historical states and future states. Furthermore, we employ a driving intention-specific feature fusion, enabling the adaptive integration of historical and future embeddings for enhanced intention recognition and trajectory prediction. This model gives two-dimensional predictions for each mode of longitudinal and lateral driving behaviors and offers probabilistic future paths with corresponding probabilities, addressing the challenges of complex vehicle interactions and multi-modality of driving behaviors. Validation using real-world trajectory datasets demonstrates the efficiency and potential.

Obtaining an optimal stability condition is very important to benefit traffic flow operations for a mix of connected and automated vehicles (CAVs) and regular vehicles. In view of multiple spatial anticipations of CAV car-following models, this paper presents a stability analysis method for mixed CAV flow from the perspective of the uniform local platoon. Transfer function theory was used to derive the stability criterion of the uniform local platoon, based on which a stability chart of equilibrium speeds and CAV feedback coefficients was calculated. Numerical simulations were also performed on a segment of highway with an on-ramp using car-following models to evaluate the impacts of the stability analysis on fuel consumption and emissions [carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (${\mathrm{NO}}_{\mathrm{X}}$ )]. The stability chart indicates that by controlling CAV feedback coefficients, the optimal stability condition can be obtained, in which the uniform local platoon remains stable for all driving speeds. Moreover, the stability analysis method can reduce fuel consumption and traffic emissions.

An electric vehicle routing problem with charging time and variable travel time is developed to address some operational issues such as range limitation and charging demand. The model is solved by using genetic algorithm to obtain the routes, the vehicle departure time at the depot, and the charging plan. Meanwhile, a dynamic Dijkstra algorithm is applied to find the shortest path between any two adjacent nodes along the routes. To prevent the depletion of all battery power and ensure safe operation in transit, electric vehicles with insufficient battery power can be repeatedly recharged at charging stations. The fluctuations in travel time are implemented to reflect a dynamic traffic environment. In conclusion, a large and realistic case study with a road network in the Beijing urban area is conducted to evaluate the model performance and the solution technology and analyze the results.

Accurate and real-time traffic flow prediction nowadays shows more and more dependence on big transportation data. Deep learning, a powerful method for feature learning, has turned out to be an effective tool to cope with these explosive data. Recently, deep models, especially unsupervised models like deep belief networks (DBN) and stacked autoencoder (SAE), are being employed into the field of traffic research and have shown great prospect. However, there is still a vacancy in the exploration on comparing the performances of different kinds of deep architectures to find an optimal solution. In this paper, we set up two deep-learning-based traffic flow prediction models for feature extraction and performances comparison: One is a deep belief networks (DBN) based on restricted Boltzmann machines (RBMs) that have Gaussian visible units and binary hidden units, and the other is a DBN based on RBMs with all units being binary. A conclusion is drawn where the former one performs better in traffic flow prediction after a series of experiments.