The practices and guidelines presented in this report are intended as a reference document for states to improve the quality of traffic data collection and processing on high-volume routes especially. The guidelines are not intended as uniform standards that all states must follow, and they are not intended to replace existing successful practices. This report and the accompanying CD are intended to serve as a resource to state DOTs by providing information on best and common practices as well as a library of additional documents produced by state DOTs. While many of the practices are common and widely known, it is expected that this compendium assembles the various approaches being used to improve HPMS traffic data collection activities especially on high-volume routes. Following are general conclusions from this examination of current data collection and processing practices.
The definition of high-volume traffic routes varies from agency to agency. In fact, no state has a definition based solely on traffic volume. Rather high-volume locations are defined in terms of the difficulty in installing data-collecting equipment with safety of traffic personnel mentioned as the primary concern. It is recommended that states have adopted several practices to improve data collection, processing, and reporting for such routes. The practices are grouped into four major categories: (i) general, (ii) data collection equipment (iii) data collection, and (iv) data processing, quality control, and quality assurance. Descriptions of these practices are provided in Chapter 3 and illustrate how states address the issues and challenges, and include sources of further information and contacts.
Training and guidelines for field personnel involved in installing and removing equipment was identified as crucial by many states. Approaches like ramp balancing on limited access freeways, coordinating equipment installation with construction activities, and use of safety procedures are some strategies used by state DOTs to improve their data collection efforts. It was also noted that data and resource sharing is becoming an increasingly common practice among state agencies.
The use of ITS generated data for HPMS reporting is increasing. Several states like Florida, Ohio, Michigan, and Illinois have successfully used ITS data for HPMS reporting. Other states are experimenting with using ITS data sources for HPMS reporting. While quality concerns exist, ITS data have great potential especially to supplement short-term counts.
Inductive loops and pneumatic road-tubes are the prevalent equipment of choice among the state DOTs. Equipment problems were common to all states interviewed, regardless of the type of equipment and traffic conditions. Several strategies are identified to improve data collection including the use of maintenance contracts, installation guidelines, the use of advanced technologies and techniques.
Non-intrusive equipment are being tested by many states for data collection. Various technologies ranging from microwave, acoustic, laser, etc have been investigated by 10 of the 13 states interviewed. Descriptions of non-intrusive data collection equipment identify the limitations, advantages, and evaluation results and provide a guide to technology selection.
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