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

<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.

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.

This article discusses the state of the art in work zone safety in the United States (US). It describes how work zones are places where, perhaps more than anywhere else on the road network, mobility and safety are strongly linked. Historically, field crews and contractors wanted vehicles in work zones to move as slowly as possible. The article shows how the industry is starting to see a shift in such thinking with the realization that excessive delays or slow-downs not only affect traveler mobility but also gives rise to more instances of road rage and other undesirable behavior. Back in the early 2000s, the USDOT’s Federal Highway Administration (FHWA) decided that it was essential that state and highway agencies design and implement work zones which give adequate consideration to the traveler. As a result, the Work Zone Safety and Mobility Rule (Subpart J) was established. Subpart J decrees that state transportation agencies have a policy in place to consider and mitigate the safety and mobility impacts of work zones. Subpart J decrees that state transportation agencies have a policy in place to consider and mitigate the safety and mobility impacts of work zones. If there are to be significant delays as a result of work zone activity, a transportation management plan needs to be developed that encompasses the work zone itself, public information, diversions to other routes and modal shifts as appropriate. Since implementation of the Rule in 2004, state transportation agencies have worked steadily to comply, which has led to an overall improvement in the mindsets of both the public and private sectors.

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 impact of work zones on mean travel time and travel time reliability has gained attention as agencies focus on performance measurement. Travel time reliability in work zones often has been difficult for agencies to quantify because of the time and expense required to collect travel time data. Several private-sector companies have begun to sell travel time data; this availability has created an opportunity to examine cost-effectively work zone impacts on travel time reliability on a broader basis. The Virginia Department of Transportation recently acquired probe vehicle-based travel time data for 2010 from a private-sector data provider. These data were used to calculate measures of travel time reliability at 15 work zones and to examine factors that affected travel time reliability. Travel time reliability was quantified with 95th percentile travel time, a buffer index, and a planning time index. The work zones experienced a statistically significant degradation across all measures of travel time reliability as compared with baseline conditions. Work zone mean buffer index, planning time index, and 95th percentile travel time rates were higher by 48%, 18%, and 16%, respectively. Although lane closures occurred during off-peak periods, work zones that involved lane closures experienced increases in their mean buffer index, planning time index, and 95th percentile travel time with rates of 67%, 23%, and 22%, respectively. Annual average daily traffic per lane and the number of access points per mile were found to have the most obvious relationships with declines in reliability at work zones.

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

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

Pakistan has a population of over 199 million and total road network of approximately 264,400 kilometers that serve about 16.2 million vehicles of all types. According to WHO estimates, there were approximately 30,000 annual Road Crash Fatalities (RCF) in Pakistan in year 2010. Work zone crashes account for significant proportion of all traffic crashes in Pakistan due to higher crash rate as compared to other parts of the highway network. Highway work zone is referred to road area where highway construction, maintenance or activity related to utility maintenance takes place. Workers in highway work zone are exposed to a variety of hazards and face risk of injury and death from construction equipment as well as passing motor vehicles. Safety measures and better understanding of risks involved while moving through the work zone have significant effects on the overall safety climate at work zones. Mismanaged work zone traffic increases the travel time delays, safety issues, vehicle operating costs (VOC) and other associated costs. Performance measures for the work zone traffic management includes user costs (travel time delay, crash cost, VOC), incident response and clearance time, queue length and community complaint. Different work Zone Traffic Management methodologies are being practiced worldwide and extensive research has been carried out at international level on country specific highway work zone safety but in Pakistan very few studies have been carried out on highway work zones. This research aims to critically analyze the impacts of the different Work Zone Traffic Management methods and recommend the best option for Expressways / Motorways in Pakistan. For the purpose of research, the author has selected a section of Motorway (M-2). Two different work zone traffic management methods are being followed in rehabilitation of M-2 .i.e. Parallel / Adjacent Method and Median Cross-Over Method. Performance measures selected for purpose of analysis are Travel Time Delay, Crash Cost (Safety) and VOC and data collected on section of M-2. After critical analysis, it is concluded that Parallel/ Adjacent Method results in lesser Travel Time delay and lesser VOC due to higher operating speeds and thus has higher savings, whereas Median Cross over Methods yield more Crash Cost savings. Keeping in view the driving habits / skills, poor maintenance of vehicles in Pakistan and risk of fatal accidents involved in parallel /adjacent method, median cross over method is preferred.

Significant changes in road and traffic conditions in transition areas are key to traffic organization and guaranteeing safety in freeway work zones. Currently, most of the related studies on transition area use theoretical calculations, traffic and driving simulations, and the impact of different transition area conditions on drivers’ psychophysiological indicators and driving behavior are unclear. In this paper, the gap acceptance theory was used to establish a calculation method of the transition area length, and the transition area length was calculated under different closed lane widths, speed limits, and traffic volumes. Based on the results of our theoretical calculations, naturalistic driving experiments were conducted with 48 participants in 12 scenarios involving 3 lane closure forms and 4 transition area lengths, and the relationship of transition area with driving workload and vehicle speed was determined. A transition area that was too short or too long increased traffic safety risks. The overall experimental results were consistent with the theoretical calculation length, and the theoretical calculation model was reliable. Compared to unaffected straight-through vehicles, merging vehicles and vehicles affected by merging have lower speeds, higher driving workloads, and increased traffic safety risks. An increase in the number of lanes in the transition area will result in increased driving workloads and vehicle speeds. Based on the changes in vehicle deceleration points and driving workloads, the affected area of the transition area was measured. When the speed limit was 60 km/h, the upstream affected areas of the transition areas with four, three, and two lanes were 1000 m, 850 m, and 700 m, and the downstream affected areas were 450 m, 400 m, and 350 m. These research results can provide a reference for improving traffic organization and guaranteeing safety in freeway work zones.