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Suggested Citation:"Appendix D: Safe System Operations and Maintenance Practices." National Academies of Sciences, Engineering, and Medicine. 2025. A Guide to Applying the Safe System Approach to Transportation Planning, Design, and Operations. Washington, DC: The National Academies Press. doi: 10.17226/29147.
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APPENDIX D
Safe System Operations and Maintenance Practices
Appendix D provides data on how respondents appraised various Safe System operations and maintenance practices. See Table D-1 for scores related to each practice’s feasibility and impact.
Interpretive categorization of Z-scores (Feasibility and Impact columns), with a mean of zero (0) and standard deviation of one (1).
| Categories | Z-scores |
|---|---|
| High | > 1 SD above mean |
| Moderate | < 1 and > 0 |
| Low | > −1 and < 0 |
| Very Low | < −1 SD below mean |
Note: SD = standard deviation round the mean score of zero (0).
Page 80
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Suggested Citation:"Appendix D: Safe System Operations and Maintenance Practices." National Academies of Sciences, Engineering, and Medicine. 2025. A Guide to Applying the Safe System Approach to Transportation Planning, Design, and Operations. Washington, DC: The National Academies Press. doi: 10.17226/29147.
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Table D-1. Operations and Maintenance practice feasibility and impact scores (n = 33).
| Practice | Feasibility | Impact | Category |
|---|---|---|---|
| Installing leading pedestrian intervals with right-turn-on-red restrictions in areas with high pedestrian activity. | 0.750 | 0.545 | Moderate Feasibility/Moderate Impact |
| Removing roadside objects that pose a danger when impacted on a lane departure. | 0.291 | 0.597 | Moderate Feasibility/Moderate Impact |
| Including crash risk potential in prioritizations of resurfacing schedules (e.g., prioritizing surfaces with low skid resistance for resurfacing). | 0.418 | 0.327 | Moderate Feasibility/Moderate Impact |
| Providing an exclusive signal phase for pedestrians in areas in high pedestrian volumes (e.g., pedestrian scramble or “Barnes Dance”). | 0.067 | 0.286 | Moderate Feasibility/Moderate Impact |
| Developing joint action plans with emergency services partners to integrate operational planning with emergency services planning. | 0.200 | 0.091 | Moderate Feasibility/Moderate Impact |
| Integrating asset management and crash analyses to determine when roadway conditions have degraded to the point that they are increasing the likelihood and severity of crashes. | 0.062 | 0.155 | Moderate Feasibility/Moderate Impact |
| Improving signal progression on designated routes for emergency vehicles with predetermined signal linking plans. | 0.134 | 0.039 | Moderate Feasibility/Moderate Impact |
| Providing longer green times for cyclists at shared path crossings. | 0.338 | −0.236 | Moderate Feasibility/Low Impact |
| Employing an active or passive equipment maintenance and replacement system. | 0.166 | −0.127 | Moderate Feasibility/Low Impact |
| Developing a traffic guidance scheme that details the use of specific traffic control devices (e.g., signs, barriers) during crash events. | 0.444 | −0.410 | Moderate Feasibility/Low Impact |
| Keeping a detailed inventory on the condition of the agencies’ transportation assets (e.g., bridges, tunnels, pavements, signs, signals, sidewalks, street furniture, vegetation). | −0.040 | −0.002 | Low Feasibility/Low Impact |
| Routinizing network-comprehensive (including bike and sidewalk networks) winter road clearance operations (e.g., snow and ice clearing, salt spreading where applicable). | 0.025 | −0.073 | Moderate Feasibility/Low Impact |
| Providing extended clearance intervals for passively detected pedestrians at signalized intersections. | −0.046 | −0.053 | Low Feasibility/Low Impact |
| Implementing variable speed limits (VSL) on roads with high pedestrian activity at certain times and high potential for significant pedestrian-motor vehicle conflicts (e.g., school zones). | −0.332 | 0.162 | Low Feasibility/Moderate Impact |
| Incorporating roadway features beyond pavement and safety infrastructure (e.g., drainage features, street furniture, vegetation) into asset management programs. | −0.056 | −0.162 | Low Feasibility/Low Impact |
| Combining passive pedestrian detection and accessible pedestrian signals to help pedestrians with low vision safely traverse intersections. | −0.236 | 0.008 | Low Feasibility/Moderate Impact |
| Implementing VSL in the vicinity of traffic incidents. | −0.579 | 0.169 | Low Feasibility/Moderate Impact |
| Extending clearance intervals for passively detected cyclists at signalized intersections. | −0.145 | −0.334 | Low Feasibility/Low Impact |
| Implementing driving safety support systems to avoid sign and signal violations and collisions. | −0.546 | −0.039 | Low Feasibility/Low Impact |
| Implementing VSL during adverse weather conditions. | −0.346 | −0.372 | Low Feasibility/Low Impact |
| Implementing VSL at nighttime in alcohol-serving districts. | −0.569 | −0.572 | Low Feasibility/Low Impact |
Page 79
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Suggested Citation:"Appendix D: Safe System Operations and Maintenance Practices." National Academies of Sciences, Engineering, and Medicine. 2025. A Guide to Applying the Safe System Approach to Transportation Planning, Design, and Operations. Washington, DC: The National Academies Press. doi: 10.17226/29147.
×
Page 80
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Suggested Citation:"Appendix D: Safe System Operations and Maintenance Practices." National Academies of Sciences, Engineering, and Medicine. 2025. A Guide to Applying the Safe System Approach to Transportation Planning, Design, and Operations. Washington, DC: The National Academies Press. doi: 10.17226/29147.
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