APPENDIX A
Glossary of Terms

This glossary provides an introduction to terms used for SUM and rural transportation. It provides a reference for the reader and establishes a consistent basis of use for terms found in the guide. The definitions in this glossary are not intended to serve as official definitions, though many are drawn from other glossaries or research papers on the subject matter.

The glossary is organized into sets of terms related to (1) SUM, (2) rural public transit, and (3) transportation technology and services that are relevant to on-demand and/or rural transportation. In some cases, the definitions were taken verbatim from works cited at the end of this chapter; in some cases, the definitions have been paraphrased.

SUM Terminology

• Bikesharing: A service that provides travelers on-demand, short-term access to a shared fleet of bicycles, usually for a fee. Bikesharing service providers may own, maintain, and provide charging (if applicable) for the bicycle fleet (SAE International 2021).
• Carsharing: A service that provides the traveler with on-demand, short-term access to a shared fleet of motor vehicles typically through a membership; the traveler pays a fee for use. Carsharing service providers typically own and maintain the vehicle fleet and provide insurance, gasoline/charging, and parking (SAE International 2021).
• Concurrent sharing: Sharing of the same transportation vehicle, device, or service by travelers from different households and/or different traveling parties in a simultaneous manner (SAE International 2021).
• Microtransit: A technology-enabled transit service that typically uses shuttles or vans to provide pooled on-demand transportation with dynamic routing (SAE International 2021).
• Mobility as a service (MaaS): A concept envisioning integrated mobility where travelers can access multiple transportation modes over a single digital interface. MaaS primarily focuses on passenger mobility, allowing travelers to seamlessly plan, book, and/or pay for travel on a pay-as-you-go and/or subscription basis (SAE International 2021).
• Mobility management: Mobility management focuses on meeting individual customer needs through a wide range of transportation options and service providers. It also focuses on coordinating these services and providers to achieve a more efficient transportation service delivery system (FTA 2025).
• Mobility on demand (MOD): A concept envisioning an interconnected and coordinated mobility ecosystem to meet the needs of all users by providing for the safe, reliable, and efficient movement of travelers and goods. MOD offers users personalized mobility and goods delivery options upon request, matched with coordinated network strategies of service providers and operations managers (SAE International 2021).

• On-demand transportation: The ability to reserve or dispatch a service upon user request (SAE International 2021).
• Ride services: Services that provide the traveler with access to rides where the traveler is the passenger and not the operator of the vehicle (SAE International 2021).
• Scooter sharing: A service that provides the traveler on-demand, short-term access to a shared fleet of scooters for a fee. Scooter sharing service providers typically own, maintain, and provide fuel/charging (if applicable) for the scooter fleet. Service providers may also provide insurance (SAE International 2021).
• Sequential sharing: Sharing of the same transportation vehicle, device, or service by travelers from different households and/or different traveling parties one after the other (i.e., in a sequential manner) (SAE International 2021).
• Shared micromobility: The shared use of a bicycle, scooter, moped, or other low-speed vehicle or device that provides travelers with short-term access on an as-needed basis (SAE International 2021).
• Shared mobility: The shared use of a travel mode that provides travelers with access to the mode on an as-needed basis (SAE International 2021).
• Taxi: A service that provides the traveler pre-arranged and/or on-demand access to a ride service in a motor vehicle for a fee for use. Travelers can typically access this ride by scheduling trips in advance, by street hail, or by e-hail (SAE International 2021).
• Transportation network company (TNC)/ridehailing/ridesourcing: A service that provides the traveler with pre-arranged and/or on-demand access to a ride for fee using a digitally enabled application or platform (e.g., a smartphone app) to connect travelers with drivers using personal, rented, or leased motor vehicles. Digitally enabled applications are typically used for booking, electronic payment, and providing ratings (SAE International 2021).

Rural Public Transit Terminology

• ADA Accessible Vehicles in Fleet: Active vehicles in the [revenue service] fleet which meet all ADA accessibility requirements (FTA 2014).
• American Indian/Alaska Native: A person having origins in any of the original peoples of North and South America (including Central America) and who maintains tribal affiliation or community attachment. This category includes people who indicate their race as “American Indian or Alaska Native” or report entries such as Navajo, Blackfeet, Inupiat, Yupʼik, or Central American Indian groups or South American Indian groups (Wells 2021).
• Bus: A transit mode comprised of rubber-tired passenger vehicles operating on fixed routes and schedules over roadways. Vehicles are powered by [fuel types such as] diesel, gasoline, battery, [or] alternative fuel engines contained within the vehicle (FTA 2014).
• Carpooling: The formal or informal sharing of rides between drivers and travelers with similar origin-destination pairings using vehicles of two to six passengers (SAE International 2021).
• Complementary paratransit service: Transportation service required by the ADA for individuals with disabilities who are unable to use fixed route transportation systems. This service must be comparable to the level of service provided to individuals without disabilities who use the fixed route system and meet the requirements specified in Sections 37.123-137.133 of Transportation Services for Individuals with Disabilities (Part 37), Code of Federal Regulations, Title 49, Volume 1. The complementary services must be origin-to-destination service (demand response) or on-call demand response service to an accessible fixed route where such service enables the individual to use the fixed route bus system for his or her trip. Service must be provided in a corridor ¾ of a mile on either side of the bus routes (FTA 2014).
• Curb-to-curb: An operational model in which the traveler is picked up and dropped off at the curb or roadside (SAE International 2021).

• Cutaway: A vehicle in which a bus body is mounted on the chassis of a van or light-duty truck. The original van or light-duty truck chassis may be reinforced or extended. Cutaways typically seat 15 or more passengers, and typically may accommodate some standing passengers (FTA 2014).
• Demand response: A transit mode comprised of passenger cars, vans or small buses operating in response to calls from passengers or their agents to the transit operator, who then dispatches a vehicle to pick up the passengers and transport them to their destinations. A demand response operation is characterized by [vehicles that] do not operate over a fixed route or on a fixed schedule except, perhaps, on a temporary basis to satisfy a special need. Typically, the vehicle may be dispatched to pick up several passengers at different pickup points before taking them to their respective destinations and may even be interrupted en route to these destinations to pick up other passengers (FTA 2014).
• Deviated fixed route service: Transit service that operates along a fixed alignment or path at generally fixed times, but may deviate from the route alignment to collect or drop off passengers who have requested the deviation (FTA 2014).
• Dispatching and supervising: [Operations staff whose] component activities include providing supervision and clerical support for revenue vehicle movement control activities, dispatching operators and vehicles from the operating station, monitoring transit operations in communications and control centers, supervising transit operations along transit routes, and controlling the return of operators and vehicles to the operating station. These may be accomplished by conventional means or through the use of advanced technologies including automatic vehicle location, transit operations software and automated demand response dispatching systems (FTA 2014).
• Door-through-door: An operational model in which the traveler is picked up inside the building and dropped off inside the door of their destination. Typically, traveler assistance is provided (SAE International 2021).
• Door-to-door: An operational model in which the traveler is picked up at the door of their origin and dropped off at the door of their destination (SAE International 2021).
• Federally recognized tribe: A federally recognized tribe is an American Indian or Alaska Native tribal entity that is recognized as having a government-to-government relationship with the United States, with the responsibilities, powers, limitations, and obligations attached to that designation, and is eligible for funding and services from the Bureau of Indian Affairs (Wells 2021).
• Fixed-route services: Services provided on a repetitive, fixed schedule basis along a specific route with vehicles stopping to pick up and deliver passengers to specific locations; each fixed route trip serves the same origins and destinations, such as rail and bus; unlike demand responsive and vanpool services (FTA 2014).
• Indian reservation: A federal Indian reservation is an area of land reserved for a tribe or tribes under treaty or other agreement with the United States, executive order, or federal statute or administrative action as permanent tribal homelands, and where the federal government holds title to the land in trust on behalf of the tribe (Wells 2021).
• Intercity bus: Regularly scheduled public service using an over-the-road bus that operates with limited stops between two urbanized areas or that connects rural areas to an urbanized area. Intercity bus mode should only be used by private, intercity bus providers (FTA 2014).
• Minivan: A light-duty vehicle having a typical seating capacity of up to seven passengers plus a driver. A minivan is smaller, lower and more streamlined than a full-sized van, but it is typically taller and has a higher floor than a passenger car. Minivans normally cannot accommodate standing passengers (FTA 2014).
• Mobility hub: Public transportation access points with frequent transit service, connections to shared and on-demand modes, services, and enabling infrastructure such as bikesharing,

• scooter sharing, carsharing, microtransit, carpooling, on-demand air mobility, taxis, TNCs, electric vehicle charging, etc. (SAE International 2021).
• Operators: The personnel (other than security agents) scheduled to be aboard vehicles in revenue operations. [These include vehicle operators and] transit agency employees that are aboard vehicles to assist riders in boarding and alighting, securing wheelchairs, etc., typically [older adults] and persons with disabilities (FTA 2014).
• Paratransit: Types of passenger transportation which are more flexible than conventional fixed-route transit but more structured than the use of private automobiles. Paratransit includes demand response transportation services, shared-ride taxis, carpooling and vanpooling, and jitney services. Most often refers to wheelchair-accessible, demand response service (FTA 2014).
• Personal vehicles in service: Vehicles that are used by the transit provider to transport passengers in revenue service but are owned by private individuals, typically an employee of the agency or a volunteer driver (FTA 2014).
• Subscription demand response: [Service for customers in demand response transportation] where there are ongoing reservations for scheduling consistent passenger trips. These subscription services are for categorical programs, such as Medicaid, Meals-on-Wheels, sheltered workshops, independent living centers and any social service agency programs (FTA 2014).
• Tribal affiliation: Tribal affiliation means an association with federally recognized Indian tribes or bands (Wells 2021).
• Tribe: A social group composed chiefly of numerous families, clans, or generations having a shared ancestry and language (Wells 2021).
• Urbanized area (UZA): An incorporated area with a population of 50,000 or more that is designated as such by the U.S. Department of Commerce, Bureau of the Census. The Census Bureau delineates urban areas after each decennial census by applying specified criteria to decennial census and other data (FTA 2014).
• Vanpooling: The formal or informal sharing of rides between drivers and travelers with similar origin-destination pairings using vehicles of seven to 15 passengers who share the cost of a van and operating expenses, and may share driving responsibility (SAE International 2021).
• Volunteer drivers: Individuals who drive vehicles in revenue service to transport passengers for the transit provider but are not employees of the transit provider and are not compensated for their labor (FTA 2014).
• Zone-to-zone: An operational model in which the traveler is required to meet the driver at a certain location and is dropped off at a certain location. Both locations are situated within the defined boundaries of the designated service area (SAE International 2021).

Technology and Service Terminology

• Application programming interface (API): Set of rules and protocols that allows two software programs or systems to communicate with each other. APIs act as intermediaries between systems, allowing them to exchange data (Goodwin 2024).
• Automatic vehicle location (AVL): The central software used by dispatchers for operations management that periodically receives real-time updates on fleet vehicle locations. In most modern AVL systems this involves an onboard computer with an integrated Global Positioning System (GPS) receiver and mobile data communications capability (Parker 2008).
• Computer-aided dispatch (CAD): Software [that] provides decisions support tools used by transit dispatchers and supervisors to monitor operations in real time, allowing them to manage the operations proactively (handling delays, disruptions in service and incidents as they occur).

• By having the CAD system notify operations staff of problems by exception, it allows staff to focus on areas of concern without the need to personally monitor operations to identify issues (Schweiger 2016).
• Dedicated fleet: Vehicles used exclusively for public transit service of a modal classification (FTA 2014).
• Demand-response scheduling and dispatch software: Software that supports demand-response booking (reservations), scheduling, and manifest generation prior to trip completion, and trip validation, billing and reporting after trip completion. Integration with a CAD/AVL system and onboard MDTs/tablets provide the software with the capability to better support same day scheduling adjustments, implement electronic manifests and collect, in real-time, data on completed trips (Schweiger 2016).
• Directly operated: Transportation service provided directly by a transit agency, using their employees to supply the necessary labor to operate the revenue vehicles. This includes instances where an agencyʼs employees provide purchased transportation services to the agency through a contractual agreement (FTA 2014).
• First-mile/last-mile service: A [transport] service designed to connect people on either side of a transit system trip with their origin or destination. This type of service is most effective when connecting transit users to high-frequency services like buses or trains, so quick response times and coordinated schedule information are important for service attractiveness. Schedule span, on-time performance and peak productivity of either service should also be considered (AECOM and UrbanTrans North America 2023).
• Fleet sharing: Services that provide the traveler access to various types of shared vehicles or devices where the traveler is the operator (SAE International 2021).
• Free-floating model: An operational model in which a fleet of vehicles or devices that can be picked up and dropped off anywhere in the service area determined by the mobility provider and/or regulatory agency (SAE International 2021).
• Gap filler service: A [transport] service designed to increase mobility in a specific geographical area with minimal or nonexistent transit service, especially when street infrastructure, network connectivity and naturally occurring barriers make fixed route service unfeasible. These services often exist independently and work to connect riders to essential locations and services within a geographical area (AECOM and UrbanTrans North America 2023).
• General Transit Feed Specification (GTFS): A data format that provides a standardized way to share public transportation information. GTFS feeds are made up of text files that model different aspects of transit information (GTFS 2025).
• GTFS-Flex: An extension of GTFS that helps users discover flexible transit services in trip planning applications. It models non-fixed-route services like demand-responsive transportation and route deviation. GTFS-Flex helps riders find more transportation options and gives trip planners more categories of transit data to read (Schweiger 2016).
• Hybrid model: An operational model that blends characteristics of station-based and free-floating models that allows a fleet of vehicles or devices to be picked up and dropped off at either designated physical or digital stations and/or anywhere in the service area determined by the mobility provider and/or regulatory agency (SAE International 2021).
• Microtransit scheduling software: Software which contains algorithms that determine how trip origins, trip destinations, and other inputs are taken into account to produce the dynamic manifests that microtransit vehicle operators receive in the form of real-time trip details (Slosky et al. 2022).
• Mobility zones: Geographic areas with a network of shared mobility options that include either (1) predefined set of boundaries (e.g., neighborhood boundaries, school zones, etc.), or (2) a radius around a point or anchor location (e.g., mobility hub, public transit station, shared

• mobility station, government center, or a land use with high trip generation). While sizes may vary based on local context, typically most mobility zones are approximately of 3 to 5 square miles (5 to 8 square kilometers) (SAE International 2021).
• Non-dedicated vehicles: Vehicles not used exclusively for contracted service (FTA 2014).
• Non-scheduled services: Services provided on demand, rather than with predetermined fixed time points, i.e., a schedule. Non-scheduled services [in transit include] demand response, demand response taxi, vanpool, [and others] (FTA 2014).
• Purchased transportation: Transportation service provided to a public transit agency or governmental unit from a public or private transportation provider based on a written contract. The provider is obligated in advance to operate public transportation services for a public transit agency or governmental unit for a specific monetary consideration, using its own employees to operate revenue vehicles (FTA 2014).
• Replacement service: [A microtransit service that] is designed to take over for poor-performing bus service and could be preferred in cases where microtransit is more cost-effective than a fixed route. However, in most cases, microtransit is more expensive per trip than fixed route service. It is important to consider the service span, frequency and productivity of the fixed route being replaced to maintain service reliability (AECOM and UrbanTrans North America 2023).
• Rider application (rider app): A smartphone application in which a rider can plan, book, and/or pay for their transit or other mobility service. For demand-response services, riders can schedule, track and take, and may enable customer feedback (AECOM and UrbanTrans North America 2023).
• Ridesplitting/ridepooling: A concurrently shared commercial ride service in a motor vehicle where the traveler is matched with other riders traveling along a similar or identical route (SAE International 2021).
• Service area: Geographic area where the operation of a shared travel mode is allowed by either the mobility provider or regulatory agency (SAE International 2021).
• Short-term: Access to a mode of transportation for a limited period of time that is generally less than a day and measured in small time increments, such as in minutes and/or hours (SAE International 2021).
• Software as a service (SaaS): The capability provided to the consumer to use a providerʼs applications running on a cloud infrastructure. The applications are accessible from various devices through either an interface such as a web browser (e.g., web-based email), or a program interface. The consumer does not manage or control the underlying cloud infrastructure (Mell and Grance 2011).
• Station-based model: An operational model in which a fleet of vehicles or devices can only be picked up and dropped off at designated physical or digital stations within the service area determined by the mobility provider and/or regulatory agency (SAE International 2021).
• Turnkey model: In this model, also known as transportation as a service (TaaS), a contracted vendor provides microtransit technology, drivers, vehicles, and operations management (Parker 2008).
• Vehicle operator/driver app: Provides a demand-response driver with real-time trip details, including manifest and manifest changes, and navigation (AECOM and UrbanTrans North America 2023).
• Zonal-based microtransit: Model [that] operates as an on-demand transit service within a designated zone or service area. In this model, all locations and destinations within the service area are accessible to users unless previously noted as a limitation. Limitations are typically caused by land barriers, such as waterways or major highways. Flex route service does not have designated stops or deviations. It typically operates as a curb-to-curb rideshare, though passengers can sometimes be asked to utilize a designated pickup location within a close distance (AECOM and UrbanTrans North America 2023).

References

AECOM and UrbanTrans North America. (2023). Microtransit Literature Review & Case Studies. Portland, ME: GoMaine.

FTA. (2014, September 16). National Transit Database (NTD) Glossary. Retrieved from Federal Transit Administration: https://www.transit.dot.gov/ntd/national-transit-database-ntd-glossary. Last updated November 26, 2024.

FTA. (2025). Mobility Management. Retrieved from Federal Transit Administration: https://www.transit.dot.gov/ccam/mobility-management. Last updated July 7, 2025.

Goodwin, M. (2024, April 9). What Is an API? https://www.ibm.com/topics/api.

GTFS. (2025, January 10). GTFS: Making Public Transit Data Universally Available. https://gtfs.org/getting-started/what-is-GTFS.

Mell, P., and Grance, T. (2011). The NIST Definition of Cloud Computing: Recommendations of the National Institute of Standards and Technology: Special Publication 800-145. Gaithersburg, MD: National Institute of Standard and Technology “Glossary.” NIST Computer Security Resource Center. Available at https://csrc.nist.gov/glossary/term/software_as_a_service.

Parker, D. J. (2008). TCRP Synthesis 73: AVL Systems for Bus Transit: Update. Transportation Research Board of the National Academies, Washington, DC.

SAE International. (2021). JA3163 - Taxonomy of On-Demand and Shared Mobility: Ground, Aviation, and Marine. New York: SAE International.

Schweiger, C. L. (2016). ITS ePrimer: Module 7: Public Transportation. Retrieved from Intelligent Transportation Systems: Professional Capacity Building: https://www.pcb.its.dot.gov/ePrimer.aspx.

Slosky, J., Silver, F., Schnader, J., Schuchard, R., and Welch, D. (2022). Microtransit Definitions, Trends, and Applications: White Paper. Pasadena, CA: CALSTART.

Wells, A. (2021, November 1). Native American Glossary. National Institutes of Health: Office of Equity, Diversity, and Inclusion.

Abbreviations and Acronyms