Improving Pedestrian Safety at Night (2025)

Chapter: Appendix A: Exposure Context for Pedestrian Fatalities

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Suggested Citation: "Appendix A: Exposure Context for Pedestrian Fatalities." National Academies of Sciences, Engineering, and Medicine. 2025. Improving Pedestrian Safety at Night. Washington, DC: The National Academies Press. doi: 10.17226/29225.
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APPENDIX A.

Exposure Context for Pedestrian Fatalities

It is important to understand the underlying influence of exposure on pedestrian fatalities. Exposure can be represented in a variety of ways, but we gathered data on pedestrian and motor vehicle activity levels for this analysis. Currently, the best available national-level data on both pedestrian and motor vehicle travel at different times of day comes from the National Household Travel Survey (NHTS) (FHWA 2017). This survey provides the start times for trips made between pairs of origins and destinations by different types of transportation (it also includes trips made for exercise or recreational purposes). While these trips are not coded by daylight versus darkness, we analyzed the proportion of trips starting between 6:00 pm and 5:59 am as a rough approximation of nighttime trips.

While the NHTS is a large national survey, analyses of trips and miles traveled for specific modes by time of day are limited by a relatively small sample size. These data have even more variability when they are further divided by other travel or demographic characteristics. Despite these and other limitations, the NHTS can provide a high-level picture of pedestrian and vehicle activity levels by time of day. Figures A1-A3 summarize temporal patterns in pedestrian trips and vehicle miles traveled Note: We analyzed pedestrian trips rather than pedestrian miles traveled because the 2017 NHTS pedestrian miles traveled data includes some large outlier values. We think that the pedestrian trip data are more accurate.

Page 152
Suggested Citation: "Appendix A: Exposure Context for Pedestrian Fatalities." National Academies of Sciences, Engineering, and Medicine. 2025. Improving Pedestrian Safety at Night. Washington, DC: The National Academies Press. doi: 10.17226/29225.
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The title of the graph is “Pedestrian Trips and V M T by Hour of Day (N H T S 2009, 2017).” The horizontal axis shows hours from 0 to 24 in increments of 1. The vertical axis shows percentage values from 0 to 12 in increments of 2. The graph consists of four lines representing pedestrian trips and vehicle miles in 2017 and 2019, respectively. The line representing 2017 pedestrian trips (22 percent from 6 p to 6 a) begins at (0, 0.1), reaches its highest point of (11.5, 8), and ends at (23, 0.7). The line representing 2009 pedestrian trips (25 percent from 6 p to 6 a) begins at (0, 0.2), reaches its highest point of (17.5, 7.9), and ends at (23, 0.7). The line representing 2017 vehicle miles (20 percent from 6 p to 6 a begins at (0, 0.15), reaches its highest point of (16.5, 9.5), and ends at (23, 0.7). The line representing 2009 vehicle miles (22 percent from 6 p to 6 a) begins at (0, 0.2), reaches (16.5, 8), and ends at (23, 1.1). Note that the coordinate values are approximate.
Figure A1. Proportion of U. S. Pedestrian Trips and Vehicle Miles Traveled by Hour of Day, 2009 and 2017
The line graph is titled “Pedestrian Trips by Hour of Day By Month, 2017 N H T S.” The horizontal axis shows hours from 0 to 23 in increments of 1. The vertical axis shows percentage values from 0 to 10 in increments of 2. The graph consists of 13 lines representing January to December and Total. Each line is represented by a different color. All 13 lines begin around (0, 0.1) and end around (23, 0.5). The highest percentage values in each month and total are as follows: January: 10 percent. February: 9.9 percent. March: 8.7 percent. April: 10.1 percent. May: 8.5 percent. June: 9.2 percent. July: 8.5 percent. August: 6.7 percent. September: 8.6 percent. October: 8.75 percent. November: 10 percent. December: 10.4 percent. Total: 8.2 percent. Note that the percentage values are approximate.
Figure A2. Proportion of US Pedestrian Trips by Hour of Day by Month, 2017
Page 153
Suggested Citation: "Appendix A: Exposure Context for Pedestrian Fatalities." National Academies of Sciences, Engineering, and Medicine. 2025. Improving Pedestrian Safety at Night. Washington, DC: The National Academies Press. doi: 10.17226/29225.
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The line graph is titled “Percentage of Walk Trips Between 6:00 p m and 5:59 a m, 2017 N H T S.” A box within the graph reads, “In 2017, 22 percent of all walk trips started between 6:00 p m and 5:59 a m (compared to 25 percent in 2009).” The horizontal axis shows months from January to December in increments of 1. The vertical axis shows percentage values from 0 to 35 in increments of 5. The line in the graph begins at 20 percent in January, reaches 19.9 percent in March, reaches its highest point of 30.5 percent in June, then reaches 26 percent in August, 15.1 percent in October, and ends at 18 in December. Note that the coordinate values are approximate.
Figure A3. Proportion of US Pedestrian Trips between 6 pm and 6 am by Month, 2017
Page 151
Suggested Citation: "Appendix A: Exposure Context for Pedestrian Fatalities." National Academies of Sciences, Engineering, and Medicine. 2025. Improving Pedestrian Safety at Night. Washington, DC: The National Academies Press. doi: 10.17226/29225.
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Page 152
Suggested Citation: "Appendix A: Exposure Context for Pedestrian Fatalities." National Academies of Sciences, Engineering, and Medicine. 2025. Improving Pedestrian Safety at Night. Washington, DC: The National Academies Press. doi: 10.17226/29225.
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Page 153
Suggested Citation: "Appendix A: Exposure Context for Pedestrian Fatalities." National Academies of Sciences, Engineering, and Medicine. 2025. Improving Pedestrian Safety at Night. Washington, DC: The National Academies Press. doi: 10.17226/29225.
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Page 153
Next Chapter: Appendix B: Detailed Summary of Descriptive Statistics
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