A Glossary for the  of Transportation

Updated January 6, 2018

This glossary is a work in process. Future versions will be posted to 3rev.ucdavis.edu/glossary and will reflect both clarifications and addition.

Feedback is appreciated, and can be directed to 3rev@ucdavis.edu.

Glossary Objective:

The 3 Revolutions in vehicle sharing, automation, and electrification are bringing transformational changes in how people and goods move in our communities. Amid the rapid pace of these changes, the nomenclature is struggling to keep up.

It is for this reason we drafted (and will continue to update) this 3 Revolutions glossary. It should be noted this glossary was originally meant to be an internal document, intended for our team to be confident we were using a common playbook. However, we decided to share this glossary- not only to reflect the spirit of sharing among the revolutionary changes occurring in transportation, but also to seek review and input from the broader transportation community.

We invite you to join us in getting closer to ensuring that the meanings of the words we use are well-understood by those who read them.

Note: The terms are listed here nested into a set of four categories, a) Shared Vehicles and Trips, b) Automated Vehicles, c) Connected Vehicles, and d) Electric Vehicles.

Shared Vehicles and Trips:

POOLING. The term pooling describes any travel situation where riders who would not otherwise travel together share a vehicle for all or part of a trip. This includes traditional carpooling and vanpooling, which includes pre-arranged groups of people traveling from similar origins along similar routes or to similar destinations, and more flexible examples of casual carpooling, where riders and drivers are matched in real time at given pick-up destinations. More recently, pooling also includes dynamic ridesharing, which matches pooled trips in using mobile apps that can efficiently fill vacant seats. Note: Carsharing and ridesourcing may be – but are not necessarily examples of pooling.

RIDESHARING. Two definitions for this term are included here. The stark differences between these definitions create considerable confusion around the “true’ meaning of the term, and amidst this dissonance the term is best avoided.

  1. The textbook definition of ridesharing is a type of pooled travel wherein additional passengers join an existing trip, maximizing vehicle occupancy. This definition of ridesharing is synonymous with carpooling, vanpooling, real-time ridesharing or dynamic ridesharing, and pooling, and these synonyms are more appropriate descriptions of this type of pooled trip.
  2. The slang definition of ridesharing is not pooled travel and describes a paid ride-for-hire service typically using a personally owned vehicle to provide a taxi-like service to a passenger or a number of passengers traveling together (i.e. Lyft, UberX). This term is also referred to as ridesourcing (described below), ride-hailing or on-demand ride service, which are more appropriate descriptions of the service provided.

RIDEHAILING. This word was introduced to replace the slang usage of the term ridesharing. It is a service that connects drivers – of otherwise non-commercial vehicles – with passengers who are willing to pay for rides, much like traditional taxi service. Ridehailing services are not necessarily considered examples of pooling since they are often still used by individual riders or used by groups that were already traveling together. Some providers offer pooled ridesourcing, which is an example of true ridesharing. Ridesourcing operators are also referred to as Transportation Network Companies (TNCs); they usually match demand and supply services through an online platform. Ridesourcing is also referred to as ride-hailing, e-hailing, or on-demand ride service.

CARSHARING. A service for people to gain short-term access to drive cars they do not own. Carsharing services allow users to pick-up and drop-off vehicles either at the same location, or at different locations, which is then called one-way carsharing or point-to-point carsharing. Carsharing memberships may be restricted to people within a specific area, group or population. Some carsharing services are peer-to-peer, with individuals allowing others to use their personal vehicles rather than primarily business-owned vehicles.  

BIKESHARING. A service in which members gain access to bicycles for short-term or short-distance trips. Bikesharing services usually allow pick-up and drop-off of bikes at different locations within a perimeter that offers the service. More recently, other hybrid or dockless systems allow bikes to be parked anywhere (including a dock for hybrid systems) within a service area providing more flexibility to their members.  Maintenance and operation costs included in the membership or usage fees are covered by the operators.

COURIER NETWORK SERVICES (CNS). A for-hire service that allows to connect senders to receivers through an online platform to schedule and pay for delivery of goods or packages (including food). The vehicles used for distribution depend on the size and characteristics of the product and delivery time (i.e. bikes, passenger vehicles, vans, trucks, or even walking). Some ridesourcing companies have expanded their services to include CNS.

MICROTRANSIT. A shuttle service with vans and/or small buses. Some microtransit service closely resemble public bus service, offering rides via fixed routes, but with fixed schedules. Others may provide flexible routes and/or demand-responsive or on-demand scheduling.

FLEXIBLE ROUTES allow users to call the microtransit shuttle from/to a given pick-up or drop-off location (i.e. to a specific bus stop, business, or home).

ON-DEMAND or DEMAND-RESPONSIVE service allows users to call a shuttle from a phone or using an app. This historically described paratransit service, and recently expanded to include taxi/ridesourcing service. On-Demand Microtransit typically includes pooling riders traveling from similar origins to similar destinations.  

PARATRANSIT. As used in the US, this is a demand-responsive service that allows users to call a ride directly from and to their chosen origin and destination, and is often offered by transit providers to conform with the Americans with Disabilities Act (ADA) which requires that the transit provider (or the local jurisdiction) provide comparable service (hours/locations) for people with disabilities who cannot use fixed-route public transit. The broader definition of paratransit is services similar to or related to transit, including carpooling, jitneys, etc.       

Automated Vehicles:

ADVANCED DRIVER ASSISTANCE SYSTEMS (ADAS). Integrated vehicle systems that improve vehicle driving operations, enhancing performance and safety. ADAS enable partial automation in a vehicle, resulting in a partially automated vehicle (SAE levels 1 to 3). Examples of ADAS include adaptive cruise control, lane departure warnings, parking assistance, surround view, forward collision avoidance, automatic emergency braking. ADAS generally does not include systems that are purely informational, such as GPS and navigation.

AUTOMATED VEHICLE (AV). This designation is commonly used for any vehicle with some level of technology that automates the act of human driving. It is largely synonymous with “autonomous”.

AUTONOMOUS VEHICLE. Same as automated, but technically means it is not “connected” to other vehicles or infrastructure. Originally used by Google, and now widely used to mean any automated vehicles. Autonomous vehicles with SAE level 4 technology are often referred to as selfdriving vehicles, while level 5 are referred to as  driverless.

DRIVERLESS VEHICLE. A vehicle that operates always without any input from a human driver. Driverless vehicles have an SAE level of 5 and are fully automated.

HIGHLY AUTOMATED VEHICLE (HAV). A vehicle that includes high levels of driving automation technology, enabling some or all operation without direct human control. HAVs have an SAE level of 4 or 5, and include both self-driving and driverless cars. HAVs may or may not have directly human operated controls (such as a steering wheel and pedals).

Society for Automotive Engineers (SAE) Levels of Driving Automation. Driving automation is a term used by the Society for Automotive Engineers (SAE) to describe the use of electronic or mechanical devices to perform driving operation tasks of a vehicle. SAE J3016 defines the levels of automation from 0 to 5.

Level 0 (no driving automation): All driving tasks are performed by the human driver.
Level 1 (assisted driving): Requires the interaction of both the human driver and one or more automated systems to perform driving tasks associated with steering and acceleration or deceleration. Other driving tasks are performed by the driver.
Level 2 (partial driving automation): Driving tasks associated with steering and acceleration or deceleration are performed completely by an automated system. The driver is responsible for monitoring the driving environment and responding appropriately.
Level 3 (conditional driving automation): An automated system performs all routine driving tasks. The driver is responsible for intervening only in unusual circumstances, such as in an accident or emergency context.
Level 4 (self-driving): An automated system performs all routine driving tasks, and has additional functionalities that enable automated response to unusual circumstances. Driver intervention is never expected or required, but it is still possible for a driver to assume temporary manual control (for instance, in the case of a system failure).
Level 5 (driverless): All driving tasks are performed by an automated system. It is not normally possible for a driver to assume manual control.

X-AS-A-SERVICE (XaaS). A term adopted from the software community that refers to any function provided to a user without the user needing to understand or manage the implementation of that service. An example of software-as-a-service is a web application, since web applications are managed by their providers rather than installed on personal computers and managed by their users. “Transportation-as-a-service (TaaS)” is the general application of XaaS to transportation. Specific transportation examples include:

VEHICLE-AS-A-SERVICE (VaaS): This term refers to the provision of vehicle fleets to companies, institutions, or the public. Rental car companies are an example of businesses engaged in VaaS because they provide vehicles to users while handling most fleet management and maintenance. Future examples of VaaS will likely rely on driving automation technology to provide vehicles more quickly, conveniently, and reliably. Also known as car-as-a-service.

MOBILITY-AS-A-SERVICE (MaaS) and TRANSPORTATION-AS-A-SERVICE (TaaS): The integration of transportation services into one commercially operated interface or application that provides end-to-end mobility options.

Connected Vehicles:

CONNECTED VEHICLES. Vehicles that are able to communicate, either directly or through intermediaries, with other vehicles, infrastructure, and devices. Automated vehicles may be connected, and connected vehicles may be automated, but they need not be integrated.

TYPES OF CONNECTIVITY: Vehicles can all use various communication protocols (4G, WiFi, dedicated short range communication (DSRC), etc.) to support their operation, such as for GPS applications, by communicating with the cloud for mapping and navigation, to report traffic or road conditions, and to obtain vehicle software updates. Some technologies (such as 4G and WiFi) connect through intermediaries (like cell towers or hotspots) while others (like DSRC) a direct communication protocols.

VEHICLE-TO-INFRASTRUCTURE (V2I). Examples of V2I connectivity include vehicle communication with traffic signals to time arrival at intersections with green lights, and smart lane markers that can be perceived even when visually obscured (for example by snow).

VEHICLE-TO-PEDESTRIANS/BICYCLISTS (V2P/B). Examples of V2P/B connectivity include warning non-drivers of dangerous situations, or preparing vehicles for a pedestrian or bicyclist the vehicle cannot yet perceive directly.

VEHICLE-TO-VEHICLE (V2V). V2V connectivity refers to communication established between vehicles to exchange information about the driving environment. This can include basic safety information such as the vehicle speed and direction or more detailed information such as road and traffic conditions. Because of the importance of low delays in these applications, most proposed approaches for V2V connectivity are direct between vehicles, rather than mediated through the cloud.

Vehicle-to-X (V2X). V2X connectivity is a general term for connectivity between vehicles and other services or entities. Automated vehicles may or may not be connected, and connected vehicles may or may not be automated. The two technology sets may support each other, with connectivity making some automation applications (for example, platooning) easier to achieve.

Electric Vehicles:

Electric or electrified transportation refers to a wide range of technologies that use electricity at some point to move a vehicle.

HYBRID ELECTRIC VEHICLE (HEV). A vehicle with an electric motor as well as an additional propulsion source (usually a liquid fuel such as gasoline). HEVs do not plug-in to the electric grid, so all energy used by the vehicle comes initially from the liquid fuel. Systems within the vehicle capture energy generated while driving  and use it to recharge the battery. There are multiple possible specific designs and levels of HEV electrification, ranging from mild to full (referring to the fraction of motive power that the electric motor can provide). Also referred to as simply a hybrid vehicle.

PLUG-IN ELECTRIC VEHICLE (PEV). A vehicle that runs partially or entirely using battery power, and is recharged through the electric grid. PEVs include:

ELECTRIC VEHICLES OR BATTERY ELECTRIC VEHICLES (EVs / BEVs): Vehicles that run on electricity stored in batteries and have an electric motor. They cannot run on liquid fuels.

PLUG-IN HYBRID ELECTRIC VEHICLES (PHEVs): PHEVs have both a gasoline- or diesel-powered engine and a battery-powered electric motor. PHEVs operate in two main modes: (1) the vehicle runs on electric power until the battery is exhausted, at which point the engine provides energy to power the batteries; or (2) the vehicle runs on electric power until the battery is exhausted, at which point both electric and gasoline modes are used. Some PHEVs are referred to as extended range electric vehicles (EREVs).

FUEL CELL ELECTRIC VEHICLE (FCEVs). FCEVs are similar to PEVs in that they run on electricity and have an electric motor. They differ in that they are powered by hydrogen stored in a tank that is converted to electricity by a fuel cell. Some FCEVs are fuel cell hybrid electric vehicles, which combine fuel-cell and battery systems and so can also be plugged into the electric grid. Also referred to as simply, fuel cell vehicles.

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