A Guide to Applying the Safe System Approach to Transportation Planning, Design, and Operations (2025)

Chapter: Appendix D: Safe System Operations and Maintenance Practices

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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
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
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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Page 79
Page 80
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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