Figure 4.
The horizontal bar chart depicts the top 20 technology keywords extracted from 4,352 railway patents between 1990 and 2023. The x-axis shows Frequency Count, and the y-axis lists Technology Keyword. Structure has the highest frequency at 495, followed by Rail at 450 and Control at 320. Signal records 295 and Prevention records 270. Electrical appears at 205, Truck at 198, Track at 175, Brake at 168, and Device at 160. Sensor shows 145, Measurement 133, Urban 130, Construction 118, High-speed 110, Manufacturing 103, Test 101, Speed 99, Circuit 95, and Concrete has the lowest frequency at 80.Visualization of top 20 technology keywords by frequency