HIGHWAY WORK ZONE SAFETY
Construction Equipment Visibility
The computer simulation procedure for developing Blind Area Diagrams was conducted using Pro-Engineer (Pro/E) CAD software. Caterpillar Inc., who conducted this procedure, provided the Pro-Engineer machine files for simulation. The Seat Index Point (SIP) coordinates were included in the Pro/E machine file for easy placement of the light test device. Maya software was used to generate the eye-point light sources, the shadows (visibility blockages), and the intersection of the shadows with the three horizontal planes (ground, 900 mm, 1500 mm). Mirrors simulated in this software were used to determine the indirect visibility areas.
Simulation Test Procedure
- Initial machine placement: The test engineer places the center of the SIP measuring device directly above the center of the visibility test circle. The best practice is to use the coordinate offsets obtained from the Pro/E model and then locate the machine geometry in the Maya software. The 20 mm forward offset of the filament center point in the location of the machine is maintained in the machine geometry Pro/E file.
- The test engineer positions the implement attachments as described in ISO 5006. The position depends on the type and size of the machine being tested.
- The test engineer positions two light sources at 680 mm above and 20 mm in front of the SIP. This point is used as the center point about which the light sources will pivot. Also, the test engineer adjusts the light source spacing for the sector of vision being recorded according to ISO 5006.
- The test engineer positions the “support bar” between the light sources perpendicular to the visibility blockage being measured. A technique called “focusing” is used to ensure that the light bar is perpendicular to the vertical blockage. The light bar is “focused” when the dark shadow, if there is one, is at its minimum width. If there is no dark shadow, the blockage does not create a masking for the given filament spacing. Horizontal blockages are created by hoods, fenders, the bottom edges of windows, etc. and do not have a single point perpendicular to the blockage. In this case, the light bar is rotated to positions that will reasonably capture the masking.
- Once a blockage has been “focused” and a blind area exists, the test engineer saves the rendered file to disk with a descriptive name of the blockage. The rendered image will be a “pie slice” since the lights in the Maya setup file have been truncated to illuminate only the geometry that is being evaluated at the time.
- The test engineer repeats steps 4 and 5 until all sectors and objects have been rendered.
- The test engineer measures indirect visibility areas of mirrors.
- The test engineer creates a new “ground plane” 900 mm above the true ground plane.
- Repeat steps 4 -7.
- The test engineer creates a new “ground plane” 1500 mm above the true ground plane.
- Repeat steps 4 -7.
- The test engineer uses PhotoShop to assemble the pie-shaped renderings into a composite image for each reference plane.