Traditional railway signal visibility check requires manual on-site measurement, which not only consumes a lot of human resources, but also may introduce error due to human factors. Based on BIM, the signal visibility check software simulates the driver's view, and scans along the alignment, intelligently combines the driver's view, the signal orientation and the signal display range together, and dynamically calculates the relative positions among the signal and the surrounding facilities and equipment.

This innovative method can accurately determine whether the driver's sight is blocked within the signal display distance, so as to find and deal with the signal display blind zone, and adjust and optimize the signal position promptly. This application relieves the tedious on-site measuring workload, reduces labor and material consumption, and significantly improves the accuracy and efficiency of the signal position design.

Fig.1 The workflow of signal visibility check based on BIM

• Start the signal visibility check software: click the signal visibility check button, and the system pops up the detection parameter setting dialog box. The user needs to set several key detection parameters in this dialog box, such as the driver's view height, the divergence angle of the signal, the display distance of the signal, and detection accuracy or step length. These parameters are used for the subsequent blind area detection calculations.

Fig.2 Interface of the signal visibility check system

• Select alignment: After parameters are set, the prompt information in the lower left corner of the operation interface guides the user to "Select Center Line/Alignment".

Fig.3 Diagram of "Select Center Line/Alignment" prompt

• Select Signal Shared Unit: when the user selects the center line, the system prompts "Select Signal Shared Unit". And the user needs to select signal shared units to be detected on the interface, namely the 3D model of the signal. This is to ensure that the detection can be performed for specific signals.

Fig.4 Diagram of "Select Signal Shared Unit" prompt

• Automatic Drawing of Signal Display Blind Zones: after the center line and signal shared units are selected, the program automatically draws the signal display blind zone in line with the previously set parameters. When drawing the blind zone, the program uses specific colors to indicate all areas where the driver cannot see the signal(red area in Figure 5). Moreover, the system also marks the specific mileage of all blind area boundaries, so that the designer can comprehend the particular scope of blind zones with a clearer perspective.

Fig.5 Diagram of Detection Flow of Signal Blind Zone

• Result Inspection and Optimization: After the check is completed, the designer optimizes the signal or adjusts the locations of other equipment and facilities that may affect the signal display aligning with the blind zone generated by the software, to ensure that the signal reaches its best display.

• Cut down labour and material resources: By a simulated driver’s view along the alignment, it no longer requires massive labour for on-site measurements like the traditional way, thereby saving labour and cost.
• Improved work efficiency: Automatic scanning and calculation process replaces manned operations, and significantly improves the work efficiency of the signal visibility check.
• Improved accuracy: intelligently merges calculating driver’s view, signal orientation and display distance, and dynamically determines the relative positions of the signal and sight obstacles, which is more accurate than traditional methods and so reduces human error.
• Timely troubleshooting and dealing with problems: the software can automatically draw the signal display blind zones, helping designers to find problems of the signal display in time such as blind zones, to quickly adjust and optimize.
• Optimized signal design: the designer can optimize the positions of signals or adjust the equipment that may affect the signal display attested by the blind zone generated by the software, to ensure the signal display reaches its best performance.