TPA traffic & parking automation

Bluetooth Overview

 

Bluetooth is a telecommunications industry specification that defines the manner in which mobile phones, computers, personal digital assistants, car radios, and other digital devices can be easily interconnected using short-range wireless communications. One example of the use of this technology is the interconnection of a mobile phone with a wireless earpiece to permit hands-free operation. The technology received its unusual name in honor of Harald Bluetooth, king of Denmark, who united Norway and Denmark during the mid-tenth century.

 

The Bluetooth capability is implemented using a low cost transceiver chip, which exchanges information with other Bluetooth devices within a globally available frequency band of 2.45 GHz.  Each device has a unique 48-bit address.  Bluetooth transmission ranges include 10 meters (33 feet) for Class 2 radios and 100 meters (330 feet) for Class 1 radios.  However, the Bluetooth traffic detection technology described here has been able to increase these ranges through appropriate adjustments to receiver sensitivity and device placement. Because of its relatively low transmission power and narrow bandwidth, Bluetooth technology offers the advantages of low power requirements that permit the use of relatively small batteries and/or solar cells for field operation.  The challenge of the technology is the implementation of roadside monitoring equipment with the sensitivity and rapid acquisition time necessary to receive Bluetooth signals from high speed traffic.

 

Bluetooth transceivers continuously transmit their 48 bit ID (address) for the purpose of identifying a device with which to communicate.  This “inquiry mode” is used to establish a link with the “responding devices”.  Inquiries are made by a Bluetooth transceiver, even while it is already engaged in communication with another device.  The continuous nature of this process facilitates the identification of passing vehicles or pedestrians containing Bluetooth devices, since all equipped and activated devices will be transmitting inquiries as long as they have their discovery mode enabled.

 

In its most basic form, the Bluetooth technology calculates travel times by matching public Bluetooth wireless network IDs at successive detection stations.  The time difference of the ID matches provides an accurate measure of travel time and an average speed based on the distance between the successive stations. Accurate measurement of distance between successive Bluetooth data collection sites is accomplished using GPS equipment installed in the Bluetooth devices that record location as a header record for the collected data.

 

The use of Bluetooth technology offers a number of advantages over existing methods in the following ways:

 

Directly measures travel time and mean speed.  This is a leapfrog advance over existing point detection technology (inductive loops, radar detectors, image processors, etc.) commonly used by most transportation agencies.  The greater accuracy of the Bluetooth units results from the fact that travel times and mean speeds are measured directly by the equipment, while these variables must be inferred from the point detection technology using speed measurements at discrete locations.

 

Measures travel times and Origin-Destinations for a variety of modes (highway vehicles, rail, and pedestrian) since the Bluetooth devices are associated with people rather than vehicles.

 

Can be applied globally due to the proliferation of the Bluetooth standard protocol. Similar techniques are available that detect the passage of toll tags (such as EZPass).  However, adequate samples of toll tags are only available in the vicinity of toll facilities.

 

Simplifies field installation procedures because of the low-power and omni-directional antenna patterns.

 

Offers a greater degree of privacy than that which can be provided with toll tag tracking, license plate surveys or cellular telephone geolocation due to the fact that there are no databases of Bluetooth addresses that can be used to associate addresses with individual owners or their vehicles.

 

Off-line BluFax Unit

 

The off-line device can be readily moved to alternate data collection sites without requiring any permanent attachment or long-term power capability.  Off-line units might be used in the vicinity of construction zones, for collection of the before-and-after data associated with a particular project or event, evaluation and calibration of other data collection methods and devices, collection of Origin-Destination data in support of a specific planning study, etc. In their portable configuration, the off-line units contain an internal battery and can operate for up to a week without recharging. Data is stored to a removable memory card. In a typical application detectors are placed from two to four miles apart along a corridor for a desired time span. At the end of the data collection period, the units are collected, data is downloaded from the memory cards and the battery is recharged. The internals of the off-line unit is shown on the photo below.

Real-time BluFax Unit

 

The real-time device is intended for long-term installations that may be associated with ongoing traffic operations and other activities requiring the continuous reporting of traffic flows in real-time.  Real-time devices might be installed on the roadways surrounding a sports arena, on freeways where displays of travel times on variable message signs are to be posted, for monitoring traffic impacts of incidents, and on arterials for real-time updates of traffic signal timing.  Real-time devices can be solar powered and rely on wireless communication for transmission of real-time data to a location for processing and display.

 

Blustats Analysis Software

 

A license for the BLUESTATS traffic data analysis software is provided with each purchase of Traffax equipment. This software has been developed for convenient matching, filtering and displaying of travel times and speeds derived from the TRAFFAX Bluetooth (BluFax) units.

 

The BLUSTATS analysis software performs the following functions:

 

 

 

 

 

 

 

 

 

The example of a BLUSTATS graphic output is shown below. It displays a traffic travel time, mean speed, and a BluFax sensors detection rate on a segment of a Don Valley Parkway highway which is running through the centre of Toronto.

The BluFax monitoring system is capable of measuring traffic and pedestrian flows. The system can be used to collect high quality, high density travel times by sampling a portion of actual travel times from the traffic stream. By matching the MAC addresses of Bluetooth devices at two different locations, not only is accurate travel time measured, privacy concerns typically associated with probe systems are minimized. Bluetooth traffic monitoring is estimated to be 100 to 1000 times more economical than drive testing on a cost per data point basis.

The sensor unit of an off-line version of the BluFax monitoring system is shown on the photo below while being deployed along a road.

BluFax Traffic Monitoring System

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