Runway Protection Zones (RPZs) Risk Assessment Tool Users’ Guide (2016)

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

24 Runway Protection Zones (RPZs) Risk Assessment Tool Users’ Guide it to both accelerated stop distance available (ASDA) and landing distance available (LDA), as shown in Figure 4.3. A user can verify the ASDA and the LDA before proceeding and can finetune the measured distances, if needed. In the dialog box shown in Figure 4.3, a user must specify the visibility minimum and the approach category associated with each runway reference code (RRC) as was shown in Figure 1.1. Categories are defined in the FAA Advisory Circular 150/5300-13A (Change 1), “Airport Design,” (February 26, 2014). RPZ_RAT automatically populates appropriate dimensions for the approach and departure RPZs according to the current FAA design standards and, upon selecting the inputs, displays the trapezoidal RPZs on the map. The tool will draw a yellow line and a blue line over the centerline of the runway as shown in Figure 4.3 on the left. The yellow line represents the LDA and the blue line represents the ASDA. Initially, these lines will overlap, assuming LDA and ASDA are equal. If, for example, there is a dis- placed threshold, a user can edit either one by right-clicking on the runway name in the sidebar and choosing Edit LDA or Edit ASDA, as shown in Figure 4.4. If Edit LDA is selected, the software will allow the user to move either end of the yellow line as shown on the left in Figure 4.5. After moving the upper end of the LDA to the new location in this example, the user clicks on the line to complete the edit. As shown in the figure on the right, the software automatically moves the approach RPZ and updates the LDA measurement according to the new landing threshold selected. When input of the runway data is complete, the tool initially assigns the same LDA and ASDA lines to the opposite runway and reverses the beginning and the end points of the lines. Opposite Figure 4.3. Entering runway data. þÿRunway Protection Zones (RPZs) Risk Assessment Tool Users  Guide Copyright National Academy of Sciences. All rights reserved.

Figure 4.4. Editing properties of a runway. Figure 4.5. Editing declared distances (LDA, ASDA) for a displaced threshold. þÿRunway Protection Zones (RPZs) Risk Assessment Tool Users  Guide Copyright National Academy of Sciences. All rights reserved.

26 Runway Protection Zones (RPZs) Risk Assessment Tool Users’ Guide runway declared distances could be similarly edited. To finalize the opposite runway input, the user must assign the appropriate visibility minimum and approach category. This is done by right-clicking on the opposite runway name and choosing Edit Properties. The tool updates the map by adding the approach and departure RPZs of the opposite runway. 4.4 Generating RPZ Crash Likelihood Contours After the steps discussed in prior sections are completed, a user can run the tool to generate the RPZ crash likelihood contours. The contours are expected to display the likelihood of a crash at any location within the RPZs. The tool is based on geographic information system (GIS) information and generates a grid system around the airport to conduct the risk analysis. Cells of the grid system that intersect the RPZs are geographically referenced, and the software calculates the distances of the cells from the runway ends and the extended centerline to conduct the risk assessment. The density of the grid system is controlled by the user by setting a cell square footage in Analysis settings. Usually, a grid system with cells of 10,000 square feet (100 feet by 100 feet) provides meaningful first estimates. A more refined grid of 100-square-foot cells (10 feet by 10 feet) provides sufficient resolution for the final analysis. The software runs the analysis for the cells within the RPZs as well as the cells through which the RPZ passes. A denser grid system provides more accurate results because the boundaries of the RPZ are more accurately approximated. Ideally, the user will always adopt the larger cell size initially. When the software set up is complete and approximate numbers are reasonable, the user should regenerate a denser grid system with smaller cells. Depending on airport size and number of runways, it may require several hours for the tool to regenerate the grid and to complete the analysis. When the grid system is generated, the software is ready to conduct the analysis, and the Run Analysis option becomes active in the sidebar. Depending on the number and the size of the RPZs and the land uses identified, as well as the number of movements in the NOD file, and the user’s computer speed, running the analysis may take only a few minutes to hours to complete. If an attempt is made to access the software while it is running, the status at the top ribbon may change to “Not Responding.” This is not an indication of a software crash, but rather a message that the tool is inaccessible before the analysis is complete. Upon completion of the analysis, the software color-codes each grid cell based on the values calculated for the crash likelihoods. Areas colored with darker shades imply a higher likelihood of an incident or accident than areas colored with lighter shades. Figure 4.6 presents a grid system with 25-foot by 25-foot cells. The crash likelihood contours and color-coded cells are illustrated on the right side of the figure. As expected, locations closer to the end of the runway and closer to the extended centerline have higher likelihoods of a crash than locations on the farther corners of the RPZ. The tool also generates a Microsoft Excel output file with detailed results and graphs which are discussed later in this guide. þÿRunway Protection Zones (RPZs) Risk Assessment Tool Users  Guide Copyright National Academy of Sciences. All rights reserved.

Getting Started with RPZ_RAT 27 Question: Assume tunneling a road passing through an RPZ is the only viable option to reduce risk and funding is sufficient only to tunnel a portion of the road, where should the road be tunneled? Answer: Start with areas of the road colored with the darkest shading. Extend the tunnel to areas with lighter shading as budget allows. When the analysis is complete, the tool prompts the user to name and save the Excel file. The likelihood contours are automatically saved on the project map. 4.5 Entering Land Uses and Conducting Risk Analysis To conduct the risk analysis, the land use data should be incorporated into the software. Given that the goal is to assess the risk to people on the ground, areas within the RPZ that may be occupied by people should be identified. A user can identify the location and dimen- sions of these land uses from airport layout plans, aerial surveys, or publicly available web sources such as Google Earth. The map feature of the tool can also be used to identify the land uses. The map feature of the tool is linked with ESRI ArcGIS maps and is updated as ESRI updates its maps. Figure 4.6. Grid system and crash likelihood contours. þÿRunway Protection Zones (RPZs) Risk Assessment Tool Users  Guide Copyright National Academy of Sciences. All rights reserved.

28 Runway Protection Zones (RPZs) Risk Assessment Tool Users’ Guide A user is not limited to analyzing what is seen on the tool map. Candidate or proposed changes to land uses may also be evaluated (e.g., a planned roadway or removal of a residential building) and its effect on the risk measured, hypothetically. There is no limitation to the shape of a land use that can be analyzed by RPZ_RAT. To add a land use, click on Create land use in the top ribbon which changes the mouse cursor to a hand. Then, follow the perimeter of the land use by making as many clicks as needed to mimic its shape as shown in Figure 4.7. To finish drawing the land use, click on the red dot. A dialog box opens to allow selection of the land use type from a dropdown menu. A user may also assign a name and a population density to the land use. After closing the dialog box, the tool displays the land use in the sidebar with the user-assigned name. The properties may be edited or the land deleted with a right click on its name. The tool does not allow modification to the shape of a land use. If adjustments are required, the user should delete the land use by a right click on its name and draw it again as a new land use. Also, when selecting a land use from the sidebar, the tool highlights the land use on the map. In establishing the population density within each land use, if the average population present within the land use and the area of the land use in square feet are known, the population density can be obtained by dividing the population by the area. The result can be directly entered in the tool. The user must follow the units of measurements identified in the tool. For the roadway example, length is entered in miles and vehicle speed is entered in miles per hour. Question: Can I enter a land use before generating the grid system? Does land use affect likelihood contours? Answer: You can input the land uses before generating the grid. In this case, the software generates the crash likelihood contours and performs the risk calculations associated with the land uses at the same time. If you only want to see the likelihood contours, you can generate the grid and run the analysis without entering the land use information. For roadways and railways, where it is harder to estimate the average number of people pres- ent at any given moment, a user may enter information such as AADT, length of the roadway Figure 4.7. Entering a land use (sample roadway). þÿRunway Protection Zones (RPZs) Risk Assessment Tool Users  Guide Copyright National Academy of Sciences. All rights reserved.