Traffic Capacity Level of Service: Adaptations and Usage (2025)
Chapter: Abbreviations and Acronyms
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Appendix D: State Guides and Reference Documents
Suggested Citation:
"Abbreviations and Acronyms." National Academies of Sciences, Engineering, and Medicine. 2025. Traffic Capacity Level of Service: Adaptations and Usage. Washington, DC: The National Academies Press.
doi: 10.17226/29143.
Abbreviations and Acronyms
| 3R | Resurfacing, Restoration, and Rehabilitation |
| AADT | Annual Average Daily Traffic |
| AASHTO | American Association of State Highway and Transportation Officials |
| ACP40 | Highway Capacity and Quality of Service Standing Committee |
| APM | Analysis Procedures Manual |
| ARR | Access Revision Request |
| ATDM | Active Traffic and Demand Management |
| BLTS | Bicycle Level of Traffic Stress |
| CAF | Capacity Adjustment Factor |
| CAV | Connected and Automated Vehicle |
| D | Directional Distribution Factor |
| DDI | Diverging Diamond Interchange |
| DHV | Design Hourly Volume |
| DOT | Department of Transportation |
| ETT | Experienced Travel Time |
| FHWA | Federal Highway Administration |
| GMA | Growth Management Act |
| HCM | Highway Capacity Manual |
| HCS | Highway Capacity Software |
| HERS-ST | Highway Economic Requirements System |
| IACR | Interchange Access Change Request |
| IAR | Interchange Access Request |
| ICAT | Intersection Control Assessment Tool |
| ICE | Intersection Control Evaluation |
| LOS | Level of Service |
| LRITP | Long-Range Intermodal Transportation Plan |
| LTS | Level of Traffic Stress |
| MAP-21 | Moving Ahead for Progress in the 21st Century Act |
| MOE | Measure of Effectiveness |
| MPO | Metropolitan Planning Organization |
| NASEM | National Academies of Sciences, Engineering, and Medicine |
| NCHRP | National Cooperative Highway Research Program |
| NHS | National Highway System |
| OLOS | Operational Level of Service |
| PCE | Passenger Car Equivalent |
| PHF | Peak-hour Factor |
| PLTS | Pedestrian Level of Traffic Stress |
| PPEAG | Planning and Preliminary Engineering Applications Guide |
Suggested Citation:
"Abbreviations and Acronyms." National Academies of Sciences, Engineering, and Medicine. 2025. Traffic Capacity Level of Service: Adaptations and Usage. Washington, DC: The National Academies Press.
doi: 10.17226/29143.
| PTI | Planning Time Index |
| QSR | Queue-Storage Ratio |
| RTOR | Right-turn-on-red |
| SAF | Speed Adjustment Factor |
| SRA | Strategic Regional Arterial |
| TDM | Transportation Demand Management |
| TIA | Traffic Impact Analysis |
| TIP | Transportation Improvement Program |
| TRB | Transportation Research Board |
| TSP | Transportation System Plan |
| TWSC | Two-way Stop-controlled |
| v/c | Volume-to-Capacity Ratio |
| VHT | Vehicle hours Traveled |
| VMT | Vehicle miles Traveled |
Suggested Citation:
"Abbreviations and Acronyms." National Academies of Sciences, Engineering, and Medicine. 2025. Traffic Capacity Level of Service: Adaptations and Usage. Washington, DC: The National Academies Press.
doi: 10.17226/29143.
Abbreviations and acronyms used without definitions in TRB publications:
| A4A | Airlines for America |
| AAAE | American Association of Airport Executives |
| AASHO | American Association of State Highway Officials |
| AASHTO | American Association of State Highway and Transportation Officials |
| ACI–NA | Airports Council International–North America |
| ACRP | Airport Cooperative Research Program |
| ADA | Americans with Disabilities Act |
| APTA | American Public Transportation Association |
| ASCE | American Society of Civil Engineers |
| ASME | American Society of Mechanical Engineers |
| ASTM | American Society for Testing and Materials |
| ATA | American Trucking Associations |
| CTAA | Community Transportation Association of America |
| CTBSSP | Commercial Truck and Bus Safety Synthesis Program |
| DHS | Department of Homeland Security |
| DOE | Department of Energy |
| EPA | Environmental Protection Agency |
| FAA | Federal Aviation Administration |
| FAST | Fixing America’s Surface Transportation Act (2015) |
| FHWA | Federal Highway Administration |
| FMCSA | Federal Motor Carrier Safety Administration |
| FRA | Federal Railroad Administration |
| FTA | Federal Transit Administration |
| GHSA | Governors Highway Safety Association |
| HMCRP | Hazardous Materials Cooperative Research Program |
| IEEE | Institute of Electrical and Electronics Engineers |
| ISTEA | Intermodal Surface Transportation Efficiency Act of 1991 |
| ITE | Institute of Transportation Engineers |
| MAP-21 | Moving Ahead for Progress in the 21st Century Act (2012) |
| NASA | National Aeronautics and Space Administration |
| NASAO | National Association of State Aviation Officials |
| NCFRP | National Cooperative Freight Research Program |
| NCHRP | National Cooperative Highway Research Program |
| NHTSA | National Highway Traffic Safety Administration |
| NTSB | National Transportation Safety Board |
| PHMSA | Pipeline and Hazardous Materials Safety Administration |
| RITA | Research and Innovative Technology Administration |
| SAE | Society of Automotive Engineers |
| SAFETEA-LU | Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (2005) |
| TCRP | Transit Cooperative Research Program |
| TEA-21 | Transportation Equity Act for the 21st Century (1998) |
| TRB | Transportation Research Board |
| TSA | Transportation Security Administration |
| U.S. DOT | United States Department of Transportation |
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