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Summary 3  crashes by 15% to 53%. Experimental studies of work-zone-intrusion alarm systems have shown mixed results, and limitations of some of these systems have been documented. A limited number of economic studies have shown benefit-cost ratios for smart work zone technologies ranging from 2.1 to 10. As indicated by the survey results, the perceived performance of smart work zone tech- nologies by state DOTs varies based on the type of technology. Traveler information systems, queue warning, and dynamic lane merge received the highest DOT performance ratings for smart work zone technologies, while notification of construction equipment entering or exiting and work zone intrusion alarms were rated the lowest for performance. The vari- ability in the DOT performance ratings for smart work zone technologies suggests a wide range of DOT experiences. Smart work zone technologies are also sometimes assessed with performance measures, which are used by state DOTs for different purposes and to varying degrees. Performance measures collected for smart work zone technologies are most often used by DOTs to identify and mitigate project-level concerns, evaluate the performance of smart work zone technologies, and improve work zone policy and procedures. Crash statistics and queue length are the most frequently employed performance measures for assessing safety and operational impacts of smart work zone technologies, respectively. The level of utilization of performance measures for smart work zone technologies varies between state DOTs, with practices such as generating dashboards for work zone projects or tracking perfor- mance measures for state routes or high-priority projects regardless of whether they include smart work zone technologies. Some state DOTs are not yet ready to set and use perfor- mance measures for smart work zone technologies. The synthesis noted some state DOT considerations for the future use of smart work zone technologies. First, there is significant DOT interest in using smart arrow boards and other devices to mark the beginning and end of the work zone to provide real-time information regarding work zone locations and generate data for possible future operational and safety analyses. These work zone location technologies have already been implemented by almost one-quarter of DOTs, and approximately half of DOTs plan to implement such technologies in the future. In addition, DOTs are exploring the future use of other smart work zone tech- nologies, such as license plate readers, temporary overheight detection, pull-off detection, downstream speed notification, excessive speed warning, electronic workers-present speed limit, connected temporary traffic signals, and applications for connected and automated (or autonomous) vehicles (CAVs) and commercial vehicles (CVs). Research and advancement of innovative smart work zone technologies continues to evolve. Various technologies for possible future use in smart work zones have been devel- oped and evaluated, such as smartphone-based alert systems, connected vehicle applica- tions, proximity alert systems for construction and workers, and automatic devices for cone placement and removal in work zones. This synthesis also identified some gaps in existing knowledge and future research needs to enhance practices for smart work zone technologies within the United States. Sugges- tions for future research include the following: ⢠Performance evaluations and economic analysis studies to demonstrate the safety benefits of smart work zone technologies. ⢠The development of a handbook on field implementation to help increase awareness, build contractor and state DOT expertise, and improve consistency. ⢠Research to advance implementation of supplemental warning systems for drivers, such as smartphone-based alert systems.
4 Use of Smart Work Zone Technologies for Improving Work Zone Safety ⢠Development of additional technologies for marking work zone locations, such as simple plug-and-play devices that can be attached to existing equipment. ⢠Creation of a guidance document for the development and use of performance measures for smart work zone technologies. ⢠The implementation of a national clearinghouse similar to the Crash Modification Factors (CMF) Clearinghouse or National Work Zone Safety Information Clearinghouse that includes data on smart work zone deployments to facilitate the sharing of knowledge among state DOTs.
5  Background Highway work zones have the potential to create significant operational and safety impacts. Mitigating these impacts continues to be a challenge for departments of transportation (DOTs) from the 50 states and the District of Columbia as a result of growing traffic demand and increased work zone activity to address the deterioration of existing infrastructure. One strategy to mitigate these impacts involves the use of smart work zone technologies such as traveler information systems, queue warning systems (QWSs), variable speed limit systems, dynamic lane merge, notification warnings of entering or exiting construction equipment, work zone intrusion alarms, and work zone location technologies. The use of smart work zone technologies helps DOTs to manage traffic and operations and disseminate information to drivers in work zones in an effort to improve mobility and safety for motorists, construction workers, and other users of the transportation system. As a result of the more widespread implementation of smart work zone technologies, there is a need for greater understanding of DOT practices regarding the use and effectiveness of these technologies, especially with respect to improving safety for motorists, construction workers, and other users of the transportation system. Objectives and Scope The objectives of the synthesis were to review and document state DOT practices regarding the use of smart work zone technologies to improve safety for motorists, construction workers, and other users of the transportation system. The scope of the synthesis includes the following topics: ⢠Dynamic warning systems (e.g., queue warning, travel time through the work zone, dynamic lane merge, work zone intrusion alarm, truck entering systems) to provide accurate notifica- tions to drivers and workers regarding work zone activity; ⢠Variable speed limit systems (e.g., radar feedback signs) to reduce vehicle speed differential in advance of and within a work zone; ⢠Integration of smart technologies with crowdsourcing systems to provide data for dynamic warning systems; ⢠Work zone location technologies; ⢠Performance measures (e.g., metrics, crash reduction, and delay reduction) for assessing the effectiveness of smart work zone technologies; ⢠Measures of return on investment in smart work zone technologies; and C H A P T E R 1 Introduction
6 Use of Smart Work Zone Technologies for Improving Work Zone Safety ⢠Data transmission issues concerning the availability of cellular service and bandwidth for the deployment of smart work zone technologies. Definitions For the purposes of this synthesis, the following definitions are used: ⢠Department of transportation: An agency from the 50 states or the District of Columbia that is responsible for implementing smart work zone technologies. ⢠Smart work zone technologies: Systems that use specialized components, such as sensors, communications, software, and electronic equipment, to manage traffic and operations and disseminate information to drivers in work zones in an effort to improve both safety and mobility in work zones for motorists, workers, and other users of the transportation system. Types of Smart Work Zone Technologies The synthesis includes all types of smart work zone technologies meeting the definition in the previous section. The more common types of smart work zone technologies are briefly described in the following list (Scriba and Atkinson 2014, Ullman et al. 2014), and figures showing example layouts for these technologies are provided after the definitions. ⢠Traveler information systems (Figure 1) disseminate data to motorists (e.g., travel times, delay, road closures, presence of work zone) regarding real-time travel conditions in advance of and within a work zone. ⢠Queue warning systems (Figure 2) monitor work zone congestion and alert approaching motorists to slowed or stop traffic. ⢠Dynamic lane-merge systems (Figure 3) such as dynamic early merge and dynamic late merge (zipper merge), encourage motorists to merge at specific locations in advance of a lane closure based on operating conditions. Under dynamic early merge, drivers are encouraged to merge early when there is no traffic congestion to ensure the smooth flow of traffic. Dynamic late merge can be used during periods of high congestion to reduce queues and maximize capacity. ⢠Dynamic speed limit systems, also known as variable speed limit systems (Figure 4), pro- vide speed limits to motorists, typically using digital speed limit signs, based on current traffic conditions in an effort to reduce vehicular speed differential in advance of and within a work zone. ⢠Work zone data collection technologies, including Work Zone Data Exchange (WZDx) stan- dards, collect various types of information for work zones (Figure 5), including worker pres- ence, activity type, and traffic volumes for work zones. ⢠Work zone location technologies, such as smart arrow boards (Figure 6), transmit real-time data regarding the position of the work zone that can be disseminated to motorists. ⢠Work zone intrusion alarms (Figure 7) alert construction workers that an errant vehicle has crossed into the work area. ⢠Notification of construction equipment entering/exiting systems (Figure 8) alert motorists that slow-moving construction equipment is entering or exiting the work area through the use of sensors and portable changeable message signs (PCMSs). Other types of smart work zone technologies include automated speed enforcement, speed feed- back signs, automated systems to install raised pavement markers, automated cone deployment systems, moveable barriers, remotely operated lane closure systems, portable traffic monitoring devices, incident management systems, and sequential warning lights.
