30th Highest Hourly Volume

An engineering standard used to determine the size of highways. Refers to the hourly volume of vehicle traffic that will be reached only thirty times or in a year, or, for 30 hours out of the total 8,760 hours in the “design” year. From research published in A Policy on Geometric Design of Rural Highways from the American Association of State Highway Officials (AASHO) in 1965. More information: US DOT (2018)

85th Percentile Speed

An engineering standard used to determine legal speed limits. Refers to the speed at or below which 85 percent of the drivers travel on a road segment based on observed study. More Information: Strong Towns (2018)


People’s ability to reach desired services and activities, which is the ultimate goal of most transport activity. Can be contrasted to mobility, which is usually more narrowly about physical movement, and transportation, which often has a connotation of being about motor vehicles, especially private passenger cars. Related, accessible design (also called universal design) can refer to
facilities that are designed to accommodate people with disabilities. More information: Litman (2022)

Active Transportation

Self-propelled, human-powered transportation. Usually means walking and bicycling. Also called Active Travel and Active Mobility. More Information: Brand et al. (2021)

Automated Vehicles

Automated vehicles are those in which information and communication technology effect safety-critical control functions (e.g., steering, throttle, or braking) without direct driver input. At the most basic level, automated vehicle technology includes driver assistance technologies like adaptive cruise control and lane-keeping assist systems. The maturity of the technology is usually described on a spectrum between levels 0 to 5, where 5 represents true independent autonomy by the vehicle anywhere in all conditions. The safety and workability of the technology beyond level 1 is still experimental, in part because a human driver needs to notice and react to at least some external events and conditions by taking over with manual operation. More information: US DOT (2023), SAE International (2022), Koopman (2021), Zipper (various).

Avoid-Shift-Improve (ASI)

An evidence-based management framework for structuring policies and investments for transportation climate action. Refers to first seeking to avoid travel such as by making communities more walkable and locating housing and destinations near one another, next shift to more efficient modes such as public transit, and finally improve vehicle equipment, especially through transportation. All elements are considered essential for deep decarbonization, they are featured in order of decarbonization potential, and they each interact with one another. The ASI is a main strategy according to the Intergovernmental Panel on Climate Change. More Information: SLOCAT Partnership on Sustainable, Low Carbon Transport (2021)

Electric Bikes (E-bikes)

E-bikes are bicycles with battery-electric motors that provide pedal-assist and/or standalone throttle power. E-bikes are usually grouped in one of three classes. Class 1 is rider assistance up to 20 MPH, Class 2 is essentially Class 1 plus a throttle for exclusive power, and Class 3 is rider assistance up to 28 MPH. E-bikes come in a variety of sizes and formats, including front-loaders (i.e., bakfiets), longtails (and midtails, or something in between a conventional frame and long tail), three-wheelers, and four-wheelers. The term “pedalec” usually refers to an e-bike that only generates power when the cyclist is pedaling. Outside of the class system, e-bikes can can also be constituted with retrofit equipment. E-bikes can be privately owned or part of public sharing systems. They can be considered both active transportation considered micromobility. More Information: People for Bikes (2023)


A measure of climate pollution from transportation to compare impacts in a standard way across modes. Stands for grams of carbon dioxide equivalents per megajoule. Sometimes refers to direct emissions from the transportation activity only, which involves a simple calculation using readily-available fuel economy and carbon content data, and sometimes includes those emissions plus wider lifecycle emissions (usually vehicle manufacturing, vehicle end-of-life considerations, upstream fuel production impacts, and some other impacts). California’s Low Carbon Fuel Standard, one of the nation’s most rigorous regulations for transportation climate pollution, uses the lifecycle gCo2e/MJ measure and hosts an information where the data and calculations are made available. The term can also be expressed in different units (e.g. pounds instead of grams, or kWH instead of MJ).

Greenhouse Gas (GHG) Emissions Inventory

A list of emission sources and the associated emissions quantified using standardized methods. The GHG Protocol provides most generally-accepted systems.


Lev nev

often implicitly refers to shared


Diff connoations, connectivity, presence of, whole system

Transportation Climate Action

Mobility first, resource efficient mobility options enabled by technology, especially electrification and mobility tech. People first and focus on demand management

Zero Emission Vehicle (ZEV)

and why not actually zerowarr


American Association of State Highway and Transportation Officials (AASHTO)


Bicycle Infrastructure Including Bikeways and Bicycle Parking

Bus Rapid Transit (BRT)

Car Dependence

Car Sewer

Climate Resilience in Transportation

Compact Development

Complete Streets

Cost of Transportation



Demand Charges

Demand-Side Management

Design and Construction Standards

Door Zone

Driver Assistance Technologies

Equity in Transportation

Farebox Ratio

Four Es

First-Mile, Last Mile (FMLM)

Frontover and backover

Gentle Density

Green Book

High Comfort

High Stress

Innovative Mobility



Jobs-Housing Balance

Land Use

Level of Service (LOS)

Lifecycle Assessment 


Mixed-Use Development

Mobility-as-a-Service (MaaS)

Mobility Hub

Mobility Wallet


Mode Share

Mode Shift

Manual on Uniform Traffic Control Devices (MUTCD)

Particulate Matter

Public Transportation

Science-Based Targets (SBTs)

Slip Turn

Speed Bumps and Speed Humps

Speed Reduction Mechanisms

Streetlight Data

Streets vs Roads

Supply-Side Management

Systemic Safety

Three Revolutions

Traffic Calming

Transit-Oriented Development (TOD)

Transportation Demand Management (TDM(

Transportation Network Company (TNC)

Transportation Master Plan (TMP)

Transportation Technology

Total Cost of Ownership 

Traffic Calming 


Technology Readiness Level (TRL)

Turn Radius

Vision Zero

Vehicle Miles Travled (VMT)

Vertical Take-off and Landing (VTOL)

Woodlands-Urban Interface (WUI)



Updated February 3, 2023

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