Travel Time Data Collection: Techniques and Applications, Study notes of Software Project Management

Download Travel Time Data Collection: Techniques and Applications and more Study notes Software Project Management in PDF only on Docsity! Traffic Engineering And Management 11. Travel Time Data Collection Chapter 11 Travel Time Data Collection 11.1 Introduction Travel time can be defined as the period of time to transverse a route between any two points of interest. It is a fundamental measure in transportation. Travel time is also one of the most readily understood and communicated measure indices used by a wide variety of users, includ- ing transportation engineers, planners, and consumers. Travel time data is useful for a wide range of transportation analyses including congestion management, transportation planning, and traveler information. Congestion management systems commonly use travel time-based performance measures to evaluate and monitor traffic congestion. In addition, some metropoli- tan areas provide real-time travel time prediction as part of their advanced traveler information systems (ATIS). Travel time data can be obtained through a number of methods. Some of the methods involve direct measures of travel times along with test vehicles, license plate match- ing technique, and ITS probe vehicles. Additionally, various sensors (e.g. inductance loop detectors, acoustic sensors) in ITS deployment collect a large amount of traffic data every day, especially in metropolitan areas. Such data can be used for travel time estimation for extensive applications when direct measurements of travel times are not available [19]. Travel time, or the time required to traverse a route between any two points of interest, is a fundamental measure in transportation. Travel time is a simple concept understood and communicated by a wide variety of applications for transportation engineers and planners. Several data collection techniques can be used to collect travel times. These techniques are designed to collect travel times and average speeds on designated roadway segments or links. Following are the different techniques available for the travel time data collection. • Test Vehicle Techniques • License Plate Matching Techniques • ITS Probe Vehicle Techniques Dr. Tom V. Mathew, IIT Bombay 1 April 2, 2012 Traffic Engineering And Management 11. Travel Time Data Collection • Emerging and Non-Traditional Techniques 11.2 Test Vehicle Techniques Travel time data using active test vehicles in combination with varying levels of instrumenta- tion: manual (clipboard and stopwatch), an electronic distance measuring instrument (DMI), or a global positioning system (GPS) receiver. It involves the use of data collection vehicle within which an observer records cumulative travel time at predefined checkpoints along a travel route. Then this information converted to travel time, speed, and delay for each segment along the survey route. There are several different methods for performing this type of data collection, depending upon the instrumentation used in the vehicle. These vehicles are instrumented and then sent into the field for travel time data collection, they are sometimes referred to as “active” test vehicles [16]. Advantages • Advanced test vehicle techniques (e.g., DMI or GPS use) result in detailed data. • Low initial cost. Disadvantages • Sources of possible error from either human or electric sources that require adequate quality control, • Data storage difficulties. 11.3 License Plate Matching Techniques Travel times by matching vehicle license plates between consecutive checkpoints with varying levels of instrumentation: tape recorders, video cameras, portable computers, or automatic license plate character recognition [16]. Advantages • Travel times from a large sample of motorists, very simple technique. • Provides a continuum of travel times during the data collection period. Dr. Tom V. Mathew, IIT Bombay 2 April 2, 2012 Traffic Engineering And Management 11. Travel Time Data Collection Leased Phone Lines Reader Unit Antenna I.D. Date Stamp, Time Stamp Tag I.D. #, Reader Unit Microwave Radio Wave, or Coaxial Cable, Tag I.D. # Antenna Spacing Varies, Typically 2−5 km AVI tag Central Computer Toll Plaza, Sign Bridge, Overpass, or Gantry Antenna Transceiver Tag I.D. # Figure 11:2: AVI Vehicle-to-Roadside Communication Process, Source: Travel Time Detection Hand Book, [16] Vehicle Location Unit Ground−Based Radio Tower Time Stamp Time Stamp Time Stamp Time Stamp Request Vehicle Location Central Computer Vehicle I.D. Vehicle I.D. Vehicle I.D. Vehicle I.D. Figure 11:3: Ground-Based Radio Navigation Communication Process, Source: Travel Time Detection Hand Book, [16] Dr. Tom V. Mathew, IIT Bombay 5 April 2, 2012 Traffic Engineering And Management 11. Travel Time Data Collection 11.5 Cellular Geo-location This experimental technology can collect travel time data by discretely tracking cellular tele- phone call transmissions. Cellular telephones are also useful to collect travel time data. Two techniques have been applied using cellular technology: cellular telephone reporting and cellular geolocating [16]. 11.5.1 Cellular Telephone Reporting An operator at the central control facility records each driver’s identification, location, and time, by monitoring the time between successive telephone calls, travel time or travel speed between reporting locations are determined. It is useful for assessment of current traffic conditions and for collecting travel time data during delays or accidents. The cellular telephone reporting method is recommended for short-term studies with low accuracy requirements. 11.5.2 Cellular Geolocation The cellular geolocating methodology discreetly tracks cellular telephone calls to collect travel time data and monitor freeway conditions. This technique utilizes an existing cellular telephone network, vehicle locating devices, and a central control facility to collect travel time data. All vehicles equipped with cellular telephones are potential probe vehicles. The system automati- cally detects cellular telephone call initiations and locates the respective probe vehicle within a few seconds. Advantages • Driver recruitment not necessary • No in-vehicle equipment to install • Large potential sample Disadvantages • Low accuracy • Privacy issues • Infrastructure dependent Dr. Tom V. Mathew, IIT Bombay 6 April 2, 2012 Traffic Engineering And Management 11. Travel Time Data Collection 11.6 Emerging and Non-Traditional Techniques Emerging or non-traditional techniques are based on using “point” vehicle detection equipment, such as inductance loop detectors or video cameras. Travel time estimation algorithms have been developed based upon measurable point parameters such as volume, lane occupancy, or vehicle headways. Image matching algorithms are used to match vehicle images or signatures captured at two consecutive observation points. Following are some of the methods used in emerging techniques [16]. 11.6.1 Extrapolation Method Estimates average travel time by spot speeds, applied for short roadway segments between de- tection devices. It is more suitable for low accuracy application. The most accurate method to measure vehicle speed with loop detectors is to place two detectors in series, which is referred to as “speed trap” or “loop trap”. The accuracy of inductance loop speed traps is dependent upon the trap length, inductance loop wire type, and consistency in design. Many inductance loop detectors are single loops; primary application is to collect vehicle counts and lane occupancy. Many research attempts have been made to utilize speed-flow relationships to estimate vehicle speeds from single loop detectors. The following 11.1 and 11.2 equations have been used to estimate spot speeds from single loop detectors [16]. Spotspeed = volume laneoccupancy × g (11.1) where, g = speed correction factor (based upon assumed vehicle length, detector configuration, and traffic conditions). Traveltime = LinkLengthinkm Spotspeedinkm hr × 3600 sec hr (11.2) 11.6.2 Vehicle Signature Matching Calculates travel time by matching unique vehicle signatures between sequential observation points. These methods can utilize a number of point detectors such as inductance loop detec- tors, weigh-in motion sensors, video cameras, and laser scanning detectors. Vehicle signatures between two consecutive locations to provide a link based travel time and speed. It provides alternative to ITS probe vehicle based on travel time measurement, in which a probe vehicle is identified and matched between two locations using a unique identification number. Dr. Tom V. Mathew, IIT Bombay 7 April 2, 2012