Open Closure

Advancing safety in short-term utility work zones: Assessing the role of work zone intrusion alert technologies (WZIATs)

<b>Objective:</b> Work zone safety is one of the top priorities for transportation agencies. In recent years, a considerable volume of research has sought to determine work zone crash characteristics and causal factors. Unlike other non–work zone–related safety studies (on both crash frequency and severity), there has not yet been a comprehensive review and assessment of methodological approaches for work zone safety. To address this deficit, this article aims to provide a comprehensive review of the existing extensive research efforts focused on work zone crash-related analysis and modeling, in the hopes of providing researchers and practitioners with a complete overview.<b>Methods:</b> Relevant literature published in the last 5 decades was retrieved from the National Work Zone Crash Information Clearinghouse and the Transport Research International Documentation database and other public digital libraries and search engines. Both peer-reviewed publications and research reports were obtained. Each study was carefully reviewed, and those that focused on either work zone crash data analysis or work zone safety modeling were identified. The most relevant studies are specifically examined and discussed in the article.<b>Results:</b> The identified studies were carefully synthesized to understand the state of knowledge on work zone safety. Agreement and inconsistency regarding the characteristics of the work zone crashes discussed in the descriptive studies were summarized. Progress and issues about the current practices on work zone crash frequency and severity modeling are also explored and discussed. The challenges facing work zone safety research are then presented.<b>Conclusions:</b> The synthesis of the literature suggests that the presence of a work zone is likely to increase the crash rate. Crashes are not uniformly distributed within work zones and rear-end crashes are the most prevalent type of crashes in work zones. There was no across-the-board agreement among numerous papers reviewed on the relationship between work zone crashes and other factors such as time, weather, victim severity, traffic control devices, and facility types. Moreover, both work zone crash frequency and severity models still rely on relatively simple modeling techniques and approaches. In addition, work zone data limitations have caused a number of challenges in analyzing and modeling work zone safety. Additional efforts on data collection, developing a systematic data analysis framework, and using more advanced modeling approaches are suggested as future research tasks.

Mitigation strategies for work zone congestion are used by transportation agencies to manage or reduce congestion through a work zone as part of the project's transportation management plan. The objective of this research is to assist agencies’ strategy selection by identifying strategies used by state transportation agencies (STAs) nationwide and their experiences. An online survey was developed to identify current, past, and future strategy implementation for projects similar to four developed scenarios: rural reconstruction, rural resurfacing, urban reconstruction, and urban resurfacing projects. The survey received 42 responses from individuals representing 28 states (responses were received from multiple districts or regions from a few states). It was found that agencies used several strategies to address different aspects of mobility and safety. Strategy selection varied between facility location and work activity. STAs also provided strategies that failed to meet expectations and identified strategies their agency plans to implement in the future. Based on the survey results and gaps in current literature, recommendations for strategy selection and future research are provided.

Transportation agencies across the U.S. are expending a great deal of effort to improve highway work zone safety. Among those efforts is a special fund for work zone enforcement established by the Indiana Department of Transportation (INDOT). The allocation of enforcement funding was based on expert knowledge and weights and scores applied to work zone characteristics considered relevant to traffic safety. The objective of the reported project was to develop a rational and defendable tool for programming police enforcement that maximizes the safety benefits of police enforcement in INDOT work zones.\nTo understand what affects work zone safety, the research team carried out an extensive literature review, designed field experiments to evaluate the effect of selected enforcement strategies on drivers’ behavior in work zones, and developed speed models incorporating the effect of police enforcement. The estimated speeds were used to derive CMFs that express the effect of the police enforcement strategy on work zone safety. Finally, the research team combined all of the developed components in a method of predicting the costs and the safety benefits in works zones under various enforcement strategies. This last method was included in the optimization tool for programming police enforcement in a group of planned work zones.\nThe described project developed an optimization tool implemented in a Microsoft Excel spreadsheet with the OpenSolver add-in. The tool is flexible, straightforward, and easy to use. The user should be able to quickly become familiar with the required input, results, and obtained solution.

Emphasis on work zone safety and improving the identification of work zone problems has been increased by recent legislation and federal programs. There is a critical need for better data related to highway work zone safety. Results are presented of an investigation to (a) determine what is known about the magnitude of highway work zone crashes, (b) examine characteristics of highway work zone crashes using the Highway Safety Information System, (c) investigate how work zone accidents are reported on police accident report forms and within state accident report systems, (d) identify critical voids in the knowledge of the relative safety of work zones, and (e) examine possible ways to address unfulfilled information needs related to work zone safety. Deficiencies of data reporting practices and issues of data needs pertaining to work zone safety are discussed. Recommendations to improve data collection and fulfill information needs are presented, including suggested data elements to be added to police accident report forms.

Highway work zone safety has been a concern nationwide and will likely draw ever increasing attention as more highway funds are invested in the maintenance of existing highways. To improve work zone safety, the Indiana Department of Transportation (DOT) established a special fund for work zone patrolling, and this study was commissioned to help the Indiana DOT achieve the maximum safety benefits within its budget constraint. With help from the Indiana DOT, a survey of project engineers was conducted to collect work zone information. The findings from the survey were linked with other available data. A random-effect negative binomial model was developed to identify the contributing factors and to estimate crash frequency in highway work zones. The results from the model provided insight for better understanding of crashes in work zones. Various factors, including roadway information, traffic volume, work zone–specific features, and police presence, were identified as things that affect crash frequency in work zones. These and other findings will be used to plan police enforcement activities in future Indiana DOT work zones.

The Federal Highway Administration (FHWA) reported between 2016 and 2017, fatal crashes in work zones increased by 3%, while fatal crashes outside of work zones decreased by 1.5%. The FHWA also reported that work zones account for approximately 10% of the nation’s overall congestion and 24% of unexpected interstate delays. This paper reports on a study of 23 construction work zones that covered approximately 150 centerline miles of Indiana interstate roadway in the summer of 2019. Approximately 50% of all interstate crashes for the period of May to September 2019 occurred within or in an approach upstream or downstream of one of these work zones. Commercially available vehicle hard-braking event data is used for the study and geofenced to the work zone approaches and limits. This research examined 196,215 hard-braking events over a 2-month period in the summer of 2019 and 3132 crashes over the same 2-month period in 2018 and 2019 for the 23 interstate work zones. The study found there were approximately 1 crash/mile for every 147 hard-braking events in and around a construction site. The R2 was approximately 0.85. The paper concludes by recommending that hard-braking event data be used by agencies to quickly identify emerging work zone locations that show relatively large number of hard-braking events for further evaluation.

Median openings are an effective traffic organization mode for freeway crossover work zones, and their length is one of the most important control indicators to ensure traffic safety in work zones. In this paper, a theoretical calculation model of the median opening length was established according to the lane-changing demands of vehicles crossing through the median opening of the freeway. Based on the calculation model, the influencing factors of the median opening length were analyzed, and the calculation values of the median opening length under different speed limits, median widths and cross slopes were proposed. A naturalistic driving experiment of drivers’ safety and comfort, with 48 participants at four opening lengths of 40, 70, 100 and 130 m in a typical freeway work zone, was carried out based on the calculated length values and the driving workload, expressing drivers’ safety and comfort. It was found that the median opening length of the freeway had a positive correlation with the vehicles’ running speed and the drivers’ driving workload: the shorter length reduced the running speed of the vehicles and led to uncoordinated running speeds in the work zone; the longer length caused driver tension and led to the vehicles’ running speed and speed variability being too high. The research results indicated that the median opening length of freeway work zones is an important factor affecting the vehicle running speed, driving workload and speed limit compliance rate.

Mobile construction operations that are conducted at night and do not employ positive barrier systems present significant safety hazards for workers and motorists. As part of several research studies on the effectiveness of traffic control devices to enhance work zone safety, the authors investigated the impacts of construction equipment and operations on safety and exposed how a contractor could use the construction operations advantageously to benefit work zone safety. Five preservation (re-paving) projects on high-speed roadways were selected for data collection. On each project, traffic speeds were recorded prior to and at multiple points within the work zones while the work was conducted. The results reveal that the presence of large construction equipment in the work area impacts driver speed. Vehicles begin to slow down approximately 0.2 to 0.6 mi. before reaching the paver, and then increase over approximately the same distance after the paver. The amount of decrease in speed ranged from approximately 5 to 25 mph. In addition, the lateral distance between vehicles and construction equipment was also found to impact vehicle speeds. The findings reveal that contractors can utilize the presence of equipment and strategically-planned operations to benefit safety in work zones. While the findings are applicable to mobile construction operations on high-speed roadways, it is expected that equipment could be used and operations planned strategically on other types of projects, such as building projects, to benefit safety in a similar manner.

Safety of work zones is a major area of concern since it is not always possible to maintain a level of safety comparable to that of a normal highway not under construction. Proper traffic control is critical to the safety of work zones. However, traffic control devices themselves may pose a safety hazard when impacted by errant vehicles. The impact performance of many work zone traffic control devices is mostly unknown, and little, if any, crash testing has been conducted in accordance with guidelines set forth in NCHRP Report 350. The Texas Department of Transportation (TxDOT) has, in recent years, sponsored a number of studies at the Texas Transportation Institute to assess the impact performance of various work zone traffic control devices, including plastic drums and sign substrates, temporary and portable sign supports, plastic cones, vertical panels, and barricades. The results, findings, conclusions, and recommendations are presented for temporary and portable sign supports, plastic drums, sign substrates for use with plastic drums, traffic cones, and vertical panels, whereas those for barricades are covered elsewhere. Most of the work zone traffic control devices satisfactorily met the evaluation criteria set forth in NCHRP Report 350 and are recommended for field implementation. However, some of the devices failed to perform satisfactorily and are not recommended for field applications. The results from these studies are being incorporated into the TxDOT barricade and construction standard sheets for use in work zones.

Highway work zones are associated with significant adverse impacts on safety. Mitigating these impacts can be achieved by implementing several countermeasures. This paper uses controlled experiments in a driving simulator to investigate the effects of physical and digital temporary traffic control countermeasures on work zone safety. These include variable message signs, dynamic speed displays, rumble strips, and lane widths. 116 participants were recruited for the experiment. A linear mixed-effects model was developed to capture the effects of these countermeasures on average travel speed and standard deviation of speeds in the advanced warning area and within the work zone itself. The results reveal that rumble strips installed within the work zone cause the strongest reduction in speeds. Narrower lanes cause smaller speed reductions. In general, the effects of temporary traffic control countermeasures on speeds were local and were not retained beyond their proximity.

Work zones are unique construction sites having multiple elements and complex scenarios. Existing studies have utilized crash data to explore the key factors contributing to work zone crashes. However, studies covering various elements comprehensively are missing, especially in Indiana. Also, there is a lack of studies exploring how to identify the representative scenarios from a large number of work zone crashes. Thus, this study aims to investigate the key factors contributing to work zone crashes covering multiple elements and propose a procedure to select representative scenarios based on crash data. Three Indiana crash data resources and the Natural Language Processing method were applied. There are several key findings. The key factors from multiple resources were summarized, including road conditions, work zone elements, and environment. Traffic activities were the top factors, followed by construction vehicles and weather conditions. Then, a seven-step procedure to extract the representative scenarios from crash records was proposed. Applying the procedure, two representative cases were identified from Indiana crash data. The study enhances the comprehensive understanding of work zone crashes based on large- scale data and helps improve safety for workers, drivers, and pedestrians.

Improving construction work zone safety using technology: A systematic review of applicable technologies

Key Factors Analysis of Work Zone Safety and Mobility based on Micro-simulation

Intelligent work zone (IWZ) systems use innovative technologies in real time to mitigate the negative impacts of work zones on the traveling public. The automatic queue detection (AQD) system is one type of IWZ being promoted by the Federal Highway Administration. Several field studies found that AQD systems were successful in reducing average travel speeds which led to a reduction in the number of rear-end crashes and in user costs. It has been shown that well-calibrated microsimulation models are appropriate analysis tools for traditional work zone traffic. To date, there are no tools in the literature that have been developed for AQD operations that have been calibrated and validated with empirical data. This paper aims to fill this gap by providing a comprehensive guideline for calibrating and validating a microsimulation model that can emulate traffic conditions and their impacts on freeway IWZ equipped with AQD systems. Specifically, the methodology includes (1) developing the base work zone model, (2) replicating the AQD warning messages, (3) calibrating the key simulation parameters using three types of data, and (4) validating the resulting simulation model using segment travel times. This comprehensive approach was demonstrated on a Nebraska work zone that was equipped with an AQD system. VISSIM simulation model was used for the underlying tool in the demonstration. The results presented in this paper are useful to both practitioners and scholars who wish to study the impact of the IWZ accurately through microsimulation.