Yi-Cheng Chen, Yu-Shuen Wang, Wen-Chieh Lin, Wei-Xiang Huang, I-Chen Lin.
EuroVis 2015 (Computer Graphics Forum, Vol. 34, No. 3).
(a) Our system draws color-coded charts of a region within a time span to convey traffic situations.
(b) By a simple click, our system plots the locations of the visualized VDs on the map to reveal the geography and helps experts make sense of traffic situations
Our system provides semantic zoom for users to explore traffic events at different scales. From left to right are the color-coded charts at local, meso, and global scales.
Visualization of vehicle detection (VD) data is essential because the data play an important role in traffic control and policy development. Most previous works focus on visualizing trajectories obtained from global positioning system (GPS), which are detailed but less representative. In contrast, VD data report the traffic statistic at each sensing site during a time span, including speed, flow, and occupancy of each lane, which contain comprehensive traffic information for analysis. In this work, we visualize three-year VD data of freeways in Taiwan. The visualization depicts the traffic situation at a site over time using a color-coded chart that extends from left to right over time. The charts are vertically stacked and horizontally aligned according to VD’s located mileage and data time, respectively, to provide global insight. Our system allows semantic zoom, which changes the chart appearance in a continuous manner, to enable macro- and micro- scopic visualizations. Analysts can explore events that span an area with different sizes and that persist a time span with various lengths. To ensure the feasibility of our visualization, before the system design, we conducted a study with experts who work in the national freeway bureau and the institute of transportation of Taiwan. We also showed our results to the experts after the prototype system was built. The feedback shows that our VD data visualization is helpful to traffic control and policy development.