Document Library

NCHRP Web-Only Document 432: Impacts and Performance of State DOT Resilience Efforts, from TRB's National Cooperative Highway Research Program, supplements NCHRP Research Report 1159 by providing detailed methods, tools, and case examples for evaluating transportation system resilience. The document supports state DOTs in developing performance-based approaches to assess and improve the effectiveness of resilience initiatives and investments.

State departments of transportation are increasingly prioritizing resilience to address disruptions from extreme weather, economic shifts, and population changes. NCHRP Research Report 1159: Measuring Impacts and Performance of State DOT Resilience Efforts* provides guidance on using resilience performance measures to evaluate and justify investments in transportation system resilience. Supplemental NCHRP Web-Only Document 432: Impacts and Performance of State DOT Resilience Efforts provides additional resources for state DOTs in developing performance-based approaches to assess and improve the effectiveness of resilience initiatives and investments.

The Safe System Approach (SSA) is a comprehensive framework that emphasizes shared responsibility, proactive design to accommodate human error, and the management of kinetic energy to prevent serious injuries and fatalities among roadway users. The SSA offers the potential for broader safety impacts than siloed or isolated safety efforts.

NCHRP Web-Only Document 451: Developing a Toolkit to Institutionalize the Safe System Approach documents the research effort underlying the development of NCHRP Research Report 1181: Toolkit for Institutionalizing the Safe System Approach.

NCHRP Research Report 1181: Toolkit for Institutionalizing the Safe System Approach, presents 30 tools designed to support the broader institutionalization of the SSA. These tools assist transportation agencies in assessing, refining, and aligning their systems, funding strategies, decision-making processes, and project delivery practices with Safe System principles. The report provides practical, proven, and emerging strategies to support meaningful implementation across departments and levels of government. It also serves as a valuable companion to existing SSA guidance by offering hands-on tools and real-world examples that help address common institutional challenges and support sustained safety outcomes within a transformed safety culture.

Artificial intelligence—especially machine learning—is rapidly entering safety-critical domains where failures can harm people, the environment, or property. This report examines how to integrate ML safely into physical systems and outlines research priorities for safety, testing, and evaluation. It argues that rigorous safety-engineering practices must be adapted to ML, requiring changes in research, training, and engineering workflows. The authors urge a shift from judging algorithms by accuracy alone to ensuring system-level safety and reliability.

This guide from TRB’s National Cooperative Highway Research Program offers strategies for state DOTs and partner agencies to build and sustain a strong risk management culture. It emphasizes preparing for evolving challenges—from infrastructure failures to supply chain disruptions—using the Key Bridge collapse in Baltimore as a recent example.

This study evaluated winter salt application efficiency on Open Graded Friction Course (OGFC) and Dense Graded (DG) pavements along I-95 in Needham, Massachusetts, to provide evidence-based winter maintenance guidance for MassDOT. The methodology incorporated field site instrumentation, maintenance tracking, direct friction measurements, crash data analysis, and an internet-based survey. However, a full data analysis was hindered by gaps in crash records and photographs, alongside unseasonably mild winters during 2023–2024 and 2024–2025. Furthermore, the survey revealed that only 12.5% of respondents currently utilize OGFC in their states, citing concerns regarding snow and ice, durability, cost, and performance failures.

Based on the limited data collected, both OGFC and DG pavement surfaces responded similarly to winter maintenance treatments regarding pavement temperature and friction. Due to the incomplete crash data and limited direct friction measurements, safety implications could not be fully investigated, and no changes to winter maintenance application rates could be recommended. Overall, the study indicates that OGFC and DG pavement types perform comparably when subjected to the same winter maintenance practices.

NCHRP Web-Only Document 413: Applying the Safe System Approach to Transportation Planning, Design, and Operations is supplemental to NCHRP Report 1135: A Guide to Applying the Safe System Approach to Transportation Planning, Design, and Operations.

NCHRP Synthesis 652: Traffic Capacity Level of Service: Adaptations and Usage provides resources for state DOTs to evaluate and improve the LOS practices and policies

NCHRP Research Report 1135: A Guide to Applying the Safe System Approach to Transportation Planning, Design, and Operations, provides information for state departments of transportation and other transportation agencies to apply the holistic Safe System approach.

NCHRP Web-Only Document 431: Snapshots of Planning Practices, provides a series of illustrated "snapshots" as as a resource for transportation-planning practice development. This supplemental web-only document provides information for realistic practice implementation and program advancement and was published accompanying NCHRP Research Report 1158: Developing Snapshots for Transportation Planning.

NCHRP Research Report 1158: Developing Snapshots for Transportation Planning, chronicles the process of developing four Snapshots of Planning Practices. Snapshots are concise and visually appealing documents that report on current planning practices in use by transportation agencies across four practice areas: Complete Streets, Data Sharing for Performance Management, Collaboration on Local Freight Delivery, and Economic Analysis to Support Decision-Making.