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42 It was also noted that activities such as street repair or resur- SUGGESTIONS facing require the IPM system to be removed and reinstalled or lost. This is not unique to IPM system applications, but Based on the information gathered through this synthesis challenges the longevity of any type of roadway instrumen- effort, illuminated, active, IPM systems show potential for tation. Again, barrier- or post-mounted IPM systems are enhancing: (1) warning through school and construction less likely to be affected by roadway repair or resurfacing zones, at highwayrail crossings, at horizontal curves, and activities. during adverse weather; (2) guidance through multiple-turn lanes, at merge locations, and through tunnels; (3) regulation at intersection stop bars and where left turns are prohibited; Costs and (4) illumination at vehicle and truck inspection points and environmentally sensitive areas. Direct benefits of IPM Costs for IPM system applications range significantly, from systems in each of these applications cannot be quantified $5,000 to $100,000. Factors affecting cost include the length conclusively because few acceptable evaluations of recent and layout of the application and the subsequent number of IPM system applications have been performed, and a lack of markers required; specific features of the IPM system (e.g., installation, operation, and maintenance guidance is likely unidirectional or bidirectional displays and operational modes); confounding system performance. As such, suggestions to the availability and nature (e.g., solar) of power at the site; focus future research and accelerate successful applications the condition of the pavement and any remedial actions of IPM systems fall into two categories: (1) research and eval- required before IPM system installation; and traffic control uation and (2) standards and guidelines. requirements. In general, implementing agencies do not con- sider IPM systems to be a "low-cost" alternative to traditional traffic control devices and suggest that their use be limited to Research and Evaluation critical locations. Opportunities for federal funding to support IPM system implementation may be constrained by propri- · Development of a robust and standardized methodol- etary issues (i.e., FHWA typically requires system bids from ogy for evaluating IPM systems would help to ensure three or more vendors; patented products may not be approved that some level of consistency is achieved in the evalu- for widespread implementation). ation of these treatments. The functional breadth of more recent IPM system applications (i.e., to warn, guide, regulate, or provide illumination) requires an adaptable Perceived and Measured Effectiveness methodology that encompasses a wide range of perfor- mance measures. Few formal evaluations have been performed to determine · Agencies that currently operate IPM systems are the effectiveness of IPM systems in enhancing roadway safety, encouraged to evaluate their effectiveness and docu- operations, or aesthetics. Pedestrian crosswalk applications ment subsequent findings so that others can benefit have been most frequently studied; IPM systems have gen- from their experiences. In lieu of a standardized eval- erally been shown to increase vehicle driver awareness, uation methodology, agencies could focus on obtain- increase vehicle yielding, reduce vehicle approach speeds, ing a sufficiently large data sample over a reasonable reduce vehicle/pedestrian conflicts, and reduce pedestrian wait observation period to enhance the credibility of their times. findings. · Additional research, with the following focus, could Considering broader applications of IPM systems, addi- support subsequent development of IPM system guide- tional studies have generally shown a reduction in vehicle lines and standards: speeds, improved lane-tracking, increased road user aware- Equipment specifications addressing the illumina- ness, and high public acceptance. More recent studies have tion source, housing and lens, power source, system been conducted in response to FHWA's requirements for controller and enclosure; experimental status. Early results reported from these studies Operational specifications addressing system acti- show promise but are generally based on limited data and, as vation, marker color, marker flash rates, and chase such, cannot be considered conclusive. sequences; Installation methods including system layout and Implementing agencies provided significant anecdotal spacing; information through this synthesis effort purporting the effec- Maintenance requirements; tiveness of IPM systems in enhancing various aspects of road- Human factors (e.g., effects of glare and comprehen- way safety, operations, or aesthetics depending on the nature sion); and of the application. A high overall degree of IPM system Safety (e.g., overdriving and collision with nonillu- satisfaction was reported despite any installation or mainte- minated objects). nance challenges encountered. Further, implementing agencies · Development of an Internet-based clearinghouse could noted a high level of public support for and acceptance of support exchange of practical information (e.g., instal- IPM systems. lation lessons learned, annual maintenance costs, and
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43 warranty recommendations) regarding IPM system use · Warrants are likely not required or appropriate for IPM among public agencies. systems; IPM systems typically supplement existing traf- fic control treatments and/or devices. · Methods to describe the relationship between IPM sys- Standards and Guidelines tems and other ITS devices and systems and promote their use within ITS architectures and planning efforts could be · An expanded breadth and depth of coverage of IPM beneficial in encouraging implementation. These meth- systems within the MUTCD is encouraged. The breadth ods could consider how IPM systems would interface of IPM system application and subsequent function with communications protocols and other equipment, and suggests a similar required breadth in related standards how they could provide feedback to transportation system and guidelines. operators to report operational status.