5 research outputs found
Big Data Analytics for Network Level Short-Term Travel Time Prediction with Hierarchical LSTM and Attention
The travel time data collected from widespread traffic monitoring sensors
necessitate big data analytic tools for querying, visualization, and
identifying meaningful traffic patterns. This paper utilizes a large-scale
travel time dataset from Caltrans Performance Measurement System (PeMS) system
that is an overflow for traditional data processing and modeling tools. To
overcome the challenges of the massive amount of data, the big data analytic
engines Apache Spark and Apache MXNet are applied for data wrangling and
modeling. Seasonality and autocorrelation were performed to explore and
visualize the trend of time-varying data. Inspired by the success of the
hierarchical architecture for many Artificial Intelligent (AI) tasks, we
consolidate the cell and hidden states passed from low-level to the high-level
LSTM with an attention pooling similar to how the human perception system
operates. The designed hierarchical LSTM model can consider the dependencies at
different time scales to capture the spatial-temporal correlations of
network-level travel time. Another self-attention module is then devised to
connect LSTM extracted features to the fully connected layers, predicting
travel time for all corridors instead of a single link/route. The comparison
results show that the Hierarchical LSTM with Attention (HierLSTMat) model gives
the best prediction results at 30-minute and 45-min horizons and can
successfully forecast unusual congestion. The efficiency gained from big data
analytic tools was evaluated by comparing them with popular data science and
deep learning frameworks
Spatial-Temporal Deep Embedding for Vehicle Trajectory Reconstruction from High-Angle Video
Spatial-temporal Map (STMap)-based methods have shown great potential to
process high-angle videos for vehicle trajectory reconstruction, which can meet
the needs of various data-driven modeling and imitation learning applications.
In this paper, we developed Spatial-Temporal Deep Embedding (STDE) model that
imposes parity constraints at both pixel and instance levels to generate
instance-aware embeddings for vehicle stripe segmentation on STMap. At pixel
level, each pixel was encoded with its 8-neighbor pixels at different ranges,
and this encoding is subsequently used to guide a neural network to learn the
embedding mechanism. At the instance level, a discriminative loss function is
designed to pull pixels belonging to the same instance closer and separate the
mean value of different instances far apart in the embedding space. The output
of the spatial-temporal affinity is then optimized by the mutex-watershed
algorithm to obtain final clustering results. Based on segmentation metrics,
our model outperformed five other baselines that have been used for STMap
processing and shows robustness under the influence of shadows, static noises,
and overlapping. The designed model is applied to process all public NGSIM
US-101 videos to generate complete vehicle trajectories, indicating a good
scalability and adaptability. Last but not least, the strengths of the scanline
method with STDE and future directions were discussed. Code, STMap dataset and
video trajectory are made publicly available in the online repository. GitHub
Link: shorturl.at/jklT0