Floating car data also known as floating cellular data, is a method to determine the traffic speed on the road network. It is based on the collection of localisation data, speed, direction of travel and time information from mobile phone

Mobile phone

A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...

s in vehicles that are being driven. These data are the essential source for traffic information and for most intelligent transportation system

Intelligent transportation system

The term intelligent transportation systems refers to information and communication technology that improve transport outcomes such as transport safety, transport productivity, travel reliability, informed travel choices, social equity, environmental performance and network operation...

s (ITS). This means that every vehicle with an active mobile phone acts as a sensor for the road network. Based on these data, traffic congestion

Traffic congestion

Traffic congestion is a condition on road networks that occurs as use increases, and is characterized by slower speeds, longer trip times, and increased vehicular queueing. The most common example is the physical use of roads by vehicles. When traffic demand is great enough that the interaction...

 can be identified, travel times can be calculated, and traffic reports can be rapidly generated. In contrast to traffic camera

Traffic camera

A traffic camera is a video camera which observes vehicular traffic on a road. Typically, these are put along major roads such as highways, freeways, motorways, autoroutes and expressways, as well as arterial roads, and are connected with optical fibers buried alongside or even under the road,...

s, number plate recognition systems, and sensor loops embedded in the roadway, no additional hardware on the road network is necessary.

Different types are possible:

• Floating cellular data = cellular network
  Cellular network
  A cellular network is a radio network distributed over land areas called cells, each served by at least one fixed-location transceiver known as a cell site or base station. When joined together these cells provide radio coverage over a wide geographic area...
  
   data-based (CDMA, GSM, UMTS, GPRS): No special devices/hardware are necessary: every switched-on mobile phone becomes a traffic probe and is as such an anonymous source of information. The location of the mobile phone is determined using (1) triangulation
  Triangulation
  In trigonometry and geometry, triangulation is the process of determining the location of a point by measuring angles to it from known points at either end of a fixed baseline, rather than measuring distances to the point directly...
  
   or (2) the hand-over data stored by the network operator. As the GSM localisation is less accurate than GPS based systems, lots of devices have to be tracked and complex algorithms need to be used to extract high-quality data. For example, care must be taken not to misinterpret cellular phones on a high speed railway track that runs parallel to the road as incredibly fast journeys along the road. However, the more congestion, the more cars, the more phones and thus more probes. In metropolitan areas where traffic data are most needed the distance between antennas is lower and thus the accuracy increases. FCD based on mobile phones believe to have significant advantages over GPS-based or conventional methods such as cameras or street embedded sensors: No infrastructure or hardware is needed to be built in cars or along the road. It is much less expensive, offers more coverage of more streets, it is faster to set up (no work zones) and needs less maintenance. In 2007, GDOT accomplished a breakthrough milestone by demonstrating in Atlanta that such system can emulate very well road sensors data for section speeds.
• Electronic toll collection device data: ETC
  Electronic toll collection
  Electronic toll collection , an adaptation of military "identification friend or foe" technology, aims to eliminate the delay on toll roads by collecting tolls electronically. It is thus a technological implementation of a road pricing concept...
  
   transponders, which are uniquely identifiable, may be read not only at toll
  Toll road
  A toll road is a privately or publicly built road for which a driver pays a toll for use. Structures for which tolls are charged include toll bridges and toll tunnels. Non-toll roads are financed using other sources of revenue, most typically fuel tax or general tax funds...
  
   collection points (e.g. toll bridges) but also at many non-toll locations. This is used as a method to collect traffic flow data (which is anonymized) for the San Francisco Bay Area
  San Francisco Bay Area
  The San Francisco Bay Area, commonly known as the Bay Area, is a populated region that surrounds the San Francisco and San Pablo estuaries in Northern California. The region encompasses metropolitan areas of San Francisco, Oakland, and San Jose, along with smaller urban and rural areas...
  
  's 5-1-1
  5-1-1
  5-1-1, initially designated for road weather information, is a transportation and traffic information telephone hotline in some regions of the United States and Canada. Travelers can dial the three-digit telephone number 5-1-1 on traditional landline telephones and most mobile phones. It is an N11...
  
   service.
• Global Positioning System
  Global Positioning System
  The Global Positioning System is a space-based global navigation satellite system that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites...
  
  -based: A small number of cars (typically cars driving in a fleet, such as courier services and taxi drivers) are equipped with a box that contains a GPS receiver. The data are then communicated with the service provider using the regular on-board radio unit or via cellular network data (more expensive).

It is possible that FCD could be used as a surveillance

Surveillance

Surveillance is the monitoring of the behavior, activities, or other changing information, usually of people. It is sometimes done in a surreptitious manner...

method, although the companies deploying FCD systems give assurances that all data are anonymized in their systems, or kept sufficiently secure to prevent abuses.