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From page 29... ... 27 As a fi rst step in reliability monitoring data collection, agencies need to thoroughly evaluate the existing data sources in their region and determine how they can be leveraged to support travel time computations. After this step, agencies can take appropriate measures to determine how these sources can be integrated into the reliability monitoring system and identify where existing infrastructure should be supplemented with additional sensors or data sources. Read the entire page →
From page 30... ... 28 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY Public agencies typically own and operate the infrastructure-based detectors and the AVI systems (used for tolls) , and private, third-party sources often own and operate the AVL systems (although transit agencies are increasingly using AVL systems) Read the entire page →
From page 31... ... 29 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY Values across a screenline FullOrigin Time stamp Figure 2.2. Types of infrastructure-based data collection sources. Read the entire page →
From page 32... ... 30 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY at a frequency of one-half mile or less, they are suggested for inclusion in a reliability monitoring system. If detectors are placed less frequently on key routes, agencies may want to consider either installing more detectors or supplementing the existing detection with AVI sensors. Read the entire page →
From page 33... ... 31 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY and occupancy data with a granularity that depends on the sensor's setting. Sensors in a dual configuration can also directly report speed values. Read the entire page →
From page 34... ... 32 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY of interest in reliability calculations, processing and filtering is required to ensure that reliability computations are based on representative travel times for a given route. Techniques to perform this data processing are described in Chapter 3, and an example is illustrated in the Sacramento–Lake Tahoe, California, case study in Chapter 4. Read the entire page →
From page 35... ... 33 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY The advantage of LPR is that it can collect trip time samples from vehicles without requiring the presence of any specific device within the vehicle. However, this method has several drawbacks. Read the entire page →
From page 36... ... 34 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY RFID is an alternative for areas that do not have electronic toll collection if agencies distribute RFID tags to volunteer drivers. This was done in San Antonio, Texas, as part of the TransGuide traffic monitoring program, where 30,000 tags were distributed in the first 10 months of operation (9) Read the entire page →
From page 37... ... 35 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY example of using AVL equipment to analyze transit performance is illustrated in the San Diego, California, case study in Chapter 4. Global Positioning Satellite Any vehicle equipped with a global positioning satellite (GPS) Read the entire page →
From page 38... ... 36 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY PRIVATE SECTOR–BASED SOURCES Interview results from this project established that many public transportation agencies are interested in obtaining data from private sources in order to save time and money on data collection and processing. Although these private sources can provide data for facilities that are otherwise unmonitored (such as arterials) Read the entire page →
From page 39... ... 37 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY Data Transparency Although some providers may supply metadata on the data quality (e.g., a ranking scale) , the methods for quality assessment remain opaque. Read the entire page →
From page 40... ... 38 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY Five types of tables are commonly used in reliability monitoring systems: 1. Configuration information. Read the entire page →
From page 41... ... 39 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY Database design usually takes the form of a schema that formally describes the database structure, including the tables, their relationships, and constraints on data value types and lengths. Appendix A presents sample tables that can store information generated during all steps of the reliability monitoring computation process, from the raw data to the travel time density functions and reliability metrics. Read the entire page →
From page 42... ... 40 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY Transit incidents, such as bus collisions or disablements, can disrupt the operations of a transit system and cause major delays. Such incidents are increasingly being detected by the AVL systems used by transit agencies. Read the entire page →
From page 43... ... 41 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY scheduled and unscheduled construction events. Another option is to manually obtain construction-related information from changeable message sign logs or feeds. Read the entire page →
From page 44... ... 42 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY events. Similarly, although there may be no event at the location being examined, the query must look for events on intersecting facilities, as well as downstream of the location being examined. Read the entire page →
From page 45... ... 43 GUIDE TO ESTABLISHING MONITORING PROGRAMS FOR TRAVEL TIME RELIABILITY 6. Texas Transportation Institute. Read the entire page →

From page 29...

... 27 As a fi rst step in reliability monitoring data collection, agencies need to thoroughly evaluate the existing data sources in their region and determine how they can be leveraged to support travel time computations. After this step, agencies can take appropriate measures to determine how these sources can be integrated into the reliability monitoring system and identify where existing infrastructure should be supplemented with additional sensors or data sources.