Editing Floating car data

{{Short description|Speed data collected by vehicles}}

'''Floating car data''' ('''FCD''') in [[Traffic engineering (transportation)|traffic engineering]] and [[Road traffic control|management]] is typically timestamped geo-localization and speed data directly collected by moving vehicles, in contrast to traditional traffic data collected at a fixed location by a stationary device or observer. In a physical interpretation context, FCD provides a [[Continuum mechanics#Lagrangian description|Lagrangian]] description of the vehicle movements whereas stationary devices provide an [[Continuum mechanics#Eulerian description|Eulerian]] description. The participating vehicle acts itself consequently as a moving sensor using an onboard [[GPS receiver]] or cellular phone. The most common and widespread use of FCD is to determine the [[traffic speed]] on the [[road network]]. Based on these data, [[traffic congestion]] can be identified, travel times can be calculated, and [[traffic report]]s can be rapidly generated. In contrast to stationary devices such as [[traffic camera]]s, [[number plate recognition]] systems, and [[induction loop]]s embedded in the roadway, no additional hardware on the road network is necessary.

==Floating cellular data==
'''Floating cellular data''' is one of the methods to collect floating car data. This method uses [[cellular network]] data ([[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]] or (2) the hand-over data stored by the network operator. As [[GSM localisation]] is less accurate than GPS based systems, many phones must be tracked and complex algorithms used to extract high-quality data. For example, care must be taken not to misinterpret cellular phones on a [[high speed railway]] track near 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 [[cell site]]s is lower and thus precision increases. Advantages over GPS-based or conventional methods such as cameras or street embedded sensors include: No infrastructure or hardware 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]] demonstrated in Atlanta that such system can emulate very well road sensors data for section speeds. A 2007 study by [[George Mason University|GMU]] investigated the relationship between vehicle free flow speed and geometric variables on urban street segments using FCD.<ref>Ali, A. T., Flannery, A., & Venigalla, M. M. (2007). Prediction models for free flow speed on urban streets. Transportation Research Board 86th Annual Meeting. Washington D.C. 2007. (No. 07-1954).</ref>

==Vehicle re-identification==
[[File:TransCore RFID reader and antenna.jpg|thumb|[[RFID]] [[E-ZPass]] reader attached to the pole and its antenna (right) used in traffic monitoring in New York City by using vehicle re-identification method]]

Vehicle re-identification methods require sets of detectors mounted along the road. In this technique, a unique serial number for a device in the vehicle is detected at one location and then detected again (re-identified) further down the road. Travel times and speed are calculated by comparing the time at which a specific device is detected by pairs of sensors. This can be done using the [[MAC address]]es from [[Bluetooth]] devices,<ref>Tarnoff, Philip John, Bullock, Darcy M, Young, Stanley E, et al. ''Continuing Evolution of Travel Time Data Information Collection and Processing'','''Transportation Research Board Annual Meeting 2009 Paper #09-2030'''
TRB 88th Annual Meeting Compendium of Papers DVD</ref> or using the [[radio-frequency identification]] (RFID) serial numbers from [[Electronic Toll Collection]] (ETC) transponders (also called "toll tags").

The ETC transponders, which are uniquely identifiable, may be read not only at [[toll road|toll]] 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]]'s [[5-1-1]] service.<ref>[http://www.bayareafastrak.org/dynamic/signup/terms.html FasTrak Application and License Agreement] {{webarchive|url=https://web.archive.org/web/20140503091454/http://www.bayareafastrak.org/dynamic/signup/terms.html |date=2014-05-03 }}, '''Toll Tags:''' section, last subsection: ''You agree that the Toll Tag may be read to provide anonymous traffic flow data to the Metropolitan Transportation Commission’s ‘511’ project, a real time traffic information service. No information identifying a FasTrak account, person or vehicle using the Toll Tag will be collected by the Metropolitan Transportation Commission or ‘511’.''</ref>

In [[New York City]]'s Midtown in Motion<ref>{{cite web|url=http://www1.nyc.gov/office-of-the-mayor/news/257-11/mayor-bloomberg-new-real-time-traffic-management-system-reduce-congestion-midtown|title=Mayor Bloomberg Announces New, Real-time Traffic Management System To Reduce Congestion In Midtown Manhattan|quote=Cameras, Microwave Motion Sensors and E-ZPass Readers Provide Real-Time Information Used in Wireless Adjustments to Traffic Signals|date=July 18, 2011|access-date=April 15, 2018|publisher=[[Government of New York City|City of New York]]|archive-date=April 16, 2018|archive-url=https://web.archive.org/web/20180416012234/http://www1.nyc.gov/office-of-the-mayor/news/257-11/mayor-bloomberg-new-real-time-traffic-management-system-reduce-congestion-midtown|url-status=dead}}</ref> program, its adaptive traffic control system also use RFID readers to track movement of [[E-ZPass]] tags as a means of monitoring traffic flow. The data is fed through the government-dedicated broadband wireless infrastructure to the traffic management center to be used in adaptive traffic control of the traffic lights.<ref>{{cite news|title=New York's award-winning traffic control system|url=http://www.itsinternational.com/sections/nafta/features/new-yorks-award-winning-traffic-control-system/|accessdate=3 May 2014|newspaper=ITS International|date=January–February 2013}}</ref>

==Global Positioning System==
A small number of cars (typically [[fleet vehicle]]s 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]] method, although the companies deploying FCD systems give assurances that all data are anonymized in their systems, or kept sufficiently secure to prevent abuses.

== See also ==
* [[Traffic count]]

== References ==
{{Reflist}}

{{Authority control}}

[[Category:Advanced driver assistance systems]]
[[Category:Intelligent transportation systems]]
[[Category:Speed sensors]]
[[Category:Surveillance]]
[[Category:Transportation engineering]]