Long-term Work Zone Research Articles

Capacity characteristics of long-term work zones on signalized intersection approaches

This study explored the capacity characteristics of five long-term WZ configurations at a major signalized intersection in Toronto. In total, 1,766 cycles and 22,057 inter-vehicle headway observations were recorded using over 140 h of real-time traffic videos. The saturation flow rate ranged from 1318.7 to 1767.3 pc/hr/ln across the study sites. Interestingly, the Highway Capacity Manual WZ model was found to significantly overestimate the traffic capacity at the study sites. The analysis assessed the hypothesis that the saturation headway is further compressed when long queues are present on site. The average saturation headway during oversaturated conditions was found to be shorter by 5 to 11% across the study sites as compared to undersaturated conditions. Other influential factors such as day versus night and late-merge were assessed. The saturation flow under daytime conditions was higher by 3 to 5% as compared to nighttimes. Vehicles merging late from the closed lanes had a shorter headway as compared to vehicles approaching from the open lane by around 8 to 10%. Probability distribution functions of the saturation headway were developed, the best-fit curve for all cases was found to be the three-parameter lognormal distribution. The study also developed multiple regression equations to estimate WZ capacity reduction induced by heavy vehicles for a wide range of heavy vehicle percentages. On average, oversaturated conditions yielded a 5.4% additional flow reduction as compared to undersaturated conditions for the same HV%. Moreover, the impact of different snow conditions on the saturation flow was estimated. The fully slushy, partly slushy, and bare-and-wet snow categories resulted in headway elongation of 35.1 to 42%, 21.2 to 23.4%, and 6.2 to 12.6%, respectively. The study explains how the findings can assist transportation agencies and practitioners in improving the policies, practices, and guidelines related to WZ activities and planning.

Impact of Construction Work Zone on Urban Traffic Environment

Abstract Objectives Traffic management is challenging during construction because of the effects of traffic congestion, travel time, delay, and queue length. Long-term work zones on urban roads lead to many problems such as speed, inconvenience, and economic losses to drivers, which are focused on in previous studies. Methods Moreover, due to the construction work zone (CWZ), the impact on environmental factors such as air quality and noise levels was not focused on. Because of the building work zones, this research focused on comprehending how traffic congestion measurements and environmental factors affect urban traffic management. Findings The present research uses TransCAD to estimate air pollution due to increased traffic in the urban areas. Furthermore, three nonlinear AI-based models (ANFIS, FFNN, and SVR) and one linear black box model were developed to predict the noise level in the city, in which each contained the total traffic and speed as well as the ratio of heavy vehicles in the traffic. Novelty For traffic control, a variety of techniques are available, including video data analysis, infrared sensors, inductive loop detection, wireless sensor networks, etc. These are all practical techniques for efficient traffic management. It is necessary to conduct studies on the amount of traffic, the topography, accidents, time delays, and the level of safety offered in the work area. Construction operations are facilitated by the implementation of traffic flow, and during this process, long-term CWZs are inevitable. Therefore, the proposed model accomplishes the goal, namely that only analytical research and a few traffic diverter signs point drivers to alternate routes to their destinations.

Improved Practices for Temporary Work Zone Guide Signs

Freeway reconstruction projects often involve adding lanes and improving entrance and exit ramps. Sign supports for overhead guide signs are sometimes removed early in the project to make way for construction activities. In addition, roadside guide signs may need to be relocated and replaced with temporary guide signs. The Manual on Uniform Traffic Control Devices provides guidance for work zone guide signs in Part 6, stating that temporary guide signs shall have black legend and border on an orange background. But permanent guide signs follow Part 2 of the MUTCD, which prescribes white legend and border on a green background for guide signs in general. Thus, many long-term freeway work zones may have guide signs in both color schemes that change throughout the project as the construction work progresses. The constrained conditions often seen in these work zones can also result in guide signs that use a variety of fonts, font sizes, sign sizes, and placement positions. This paper describes the human factors study that was performed to assess motorist understanding of various work zone guide signage strategies. Based on the results, the researchers were able to develop recommendations for long-term work zone guide sign design and placement to improve uniformity for the traveling public.

Bi-level optimization of long-term highway work zone scheduling considering elastic demand

Purpose More and more work zone projects come with the needs of new construction and regular maintenance-related investments in transportation. Work zone projects can have many significant impacts socially, economically and environmentally. Minimizing the total impacts of work zone projects by optimizing relevant schedules is extremely important. This study aims to analyze the impacts of scheduling long-term work zone activities. Design/methodology/approach Optimal scheduling of the starting dates of each work zone project is determined by developing and solving using a bi-level genetic algorithm (GA)–based optimization model. The upper level sub-model is to minimize the total travel delay caused by work zone projects over the entire planning horizon, whereas the lower level sub-model is a traffic assignment problem under user equilibrium condition with elastic demand. Findings Sioux Falls network is used to develop and test the proposed GA-based model. The average and minimum total travel delays (TTDs) over generations of the proposed GA algorithm decrease very rapidly during the first 20 generations of the GA algorithm; after the 20th generations, the solutions gradually level off with a certain level of variations in the average TTD, showing the capability of the proposed method of solving the multiple work zone starting date optimization problem. Originality/value The proposed model can effectively identify the near-optimal solution to the long-term work zone scheduling problem with elastic demand. Sensitivity analysis of the impact of the elastic demand parameter is also conducted to show the importance of considering the impact of elastic demand parameter.

Deterministic and Stochastic Capacity in Work Zones: Findings from a Long-Term Work Zone

AbstractThis paper describes the development of a breakdown probability model for a long-term work zone in a suburban area. It was found that the Gompertz distribution best describes the breakdown ...

Crash severity analysis of nighttime and daytime highway work zone crashes.

IntroductionEgypt’s National Road Project is a large infrastructure project which presently aims to upgrade 2500 kilometers of road networks as well as construct 4000 kilometers of new roads to meet today’s need. This leads to an increase in the number of work zones on highways and therefore a rise in hazardous traffic conditions. This is why highways agencies are shifting towards night construction in order to reduce the adverse traffic impacts on the public. Although many studies have investigated work zone crashes, only a few studies provide comparative analysis of the difference between nighttime and daytime work zone crashes.MethodsData from Egyptian long-term highway work zone projects between 2010 and 2016 are studied with respect to the difference in injury severity between nighttime and daytime crashes by using separate mixed logit models.ResultsThe results indicate that significant differences exist between factors contributing to injury severity. Four variables are found significant only in the nighttime model and four other variables significant in the daytime model. The results show that older and male drivers, the number of lane closures, sidewise crashes, and rainy weather have opposite effects on injury severity in nighttime and daytime crashes. The findings presented in this paper could serve as an aid for transportation agencies in development of efficient measures to improve safety in work zones.

Identifying the Factors Contributing to Injury Severity in Work Zone Rear-End Crashes

Egypt’s National Road Project is a large infrastructure project aiming to upgrade the existing network of 2500 kilometers as well as constructing new roads of 4000 kilometers to meet today’s need. Increasing highway work zones eventually direct the challenges for traffic safety and mobility. Realizing the need for mitigating the impact of such a challenging scenario, this paper aims to investigate and identify the factors of work zone rear-end crash severity. In this regard, a random parameter ordered probit model was applied to analyze data on the Egyptian long-term highway work zone projects during the period of 2010 to 2017. The factors of speeding and foggy weather conditions are found to be the key indicators for modeling the random parameters. Besides, during the weekend and at nighttime, there is a higher risk of rear-end crash in work zones, while heavy and passenger vehicles are at greater risk in this regard. It is anticipated that the findings of this study would facilitate transport agencies in developing effective measures to ensure safe mobility across work zones.

Characteristics and Temporal Stability of Recurring Bottlenecks

This study applies and updates a method which identifies and quantifies the extent of traffic congestion from recurring freeway bottlenecks. Additionally, the spatiotemporal stability of bottlenecks over an extended period was tested. Over time congestion at bottlenecks may increase, may decrease, or may migrate to other nearby locations. Analysis of stability is important since prioritizing and applying treatments at bottlenecks is a multiyear process. In addition, a robust method for selecting sensitivity based parameters to identify and quantify bottleneck effects is presented. Subsequently, a systematic framework is developed for tracking and archiving the spatiotemporal changes in the recurring bottlenecks. The proposed method is demonstrated on a case study on Interstate 40 in North Carolina using three years of probe data. A congestion speed ratio detection threshold of 0.7 and a probability of activation threshold of 33% for the study area were determined from a sensitivity test to ascertain their recurrence. The method identified 13 bottlenecks with their impacts ranging from 35 to 3,278 mi-hours of congestion per year. Eight bottlenecks either newly emerged or had their queues merged or shifted between successive years. Even spatially stable bottlenecks had significant variation in their activation frequency and queue length. Exploration of the changes in bottleneck severity and locations revealed the influence of a long-term work zone in the area and the effect of the rapid growth in traffic demand. Local agencies can use this method to shortlist recurring bottlenecks and track changes to plan mitigation strategies.

Impact Assessment of Long-Term Work Zones in Arterial Roads on Commercial Activities in Dammam Metropolitan Area, Saudi Arabia

This paper assesses the impact of long-term work zones in arterial roads on commercial activities in Dammam Metropolitan area. The study focuses on two cases of long-term work zones in arterials in two major cities in Dammam Metropolitan Area. The first case is a work zone with full lanes closure on Prince Mohamed Bin Fahad Road at the south east entrance of Dammam city. The second case is a work zone with full lanes closure on King Abdul-Aziz Road at the northern entrance of Al-Khobar City. Data collection relies on field survey including questionnaires to affected business owners and managers. The questionnaire has been developed to assess the impact before and during road works period, in the work zone, on mobility and accessibility to commercial activities. Field survey includes 201 commercial activities at two work zone locations. Answers have been registered in Excel spreadsheet. Data analysis includes percentages of change, means, and standard deviation of dependent variables before and during the presence of the work zone. It was found that long-term work zones on arterials have multiple negative impacts on workers, sales, and customers. These impacts are related to lack of mobility, accessibility and reduction of parking availability during work period. Also, restaurants and travel agencies were the most effected activities by work zone presence, while banks were the least effected.

Work Zone Coordination Software Tool

Faced with a growing number of work zones, transportation agencies are being challenged to effectively manage the impacts of these zones, alleviate congestion, and maintain the safety of motorists and workers without disrupting project schedules. Coordinating work zones has already been practiced by various state departments of transportation and transportation agencies, yet there are no universal department of transportation policies that address how agencies should coordinate or consolidate projects. In addition, only a few states utilize computer tools specific to regional or corridor-based work zone coordination. State departments of transportation mostly coordinate significant and long-term projects. However, the majority of roadway projects include minor repair, roadway maintenance, bridge maintenance, surveying, and landscape and utility work that require relatively short-term work zones. The Work Zone Coordination Software tool was developed to provide the New Jersey Department of Transportation with an easy-to-use tool to evaluate the feasibility and effectiveness of coordinating short- and long-term work zones and to measure the benefits. This online tool is implemented with a web-based user interface. It integrates all scheduled and active construction projects, identifies conflicts between work zone projects, and estimates the benefits of conflict mitigation. The Work Zone Coordination Software tool works with the New Jersey work zone database by automatically importing data to provide up-to-date information to its users. However, the tool is built on a flexible framework that allows the integration of any work zone database provided that it includes all the required information.

Optimizing scheduling of long-term highway work zone projects

Abstract The impacts of work zone activities can be summarized into the following types: safety impact (on both motorists and workers), mobility impact, economic considerations, environmental concerns, user cost as well as contractor’s maintenance cost. Various interest subjects may focus on different aspects of the six areas identified above. In this study, the impacts of scheduling long-term work zone activities are analyzed from the perspective of traffic agencies and jurisdictions. A bi-level genetic algorithm (GA)-based optimization model is formulated to determine the optimal starting date of each work zone project. The upper-level subprogram minimizes the total travel time over the entire planning horizon, while the lower-level subprogram is a user equilibrium (UE) problem where all users try to find the route that minimizes their own travel time. The demand, and the number of work zones as well as their durations are assumed to be fixed and given a priori. The proposed GA model is applied to the Sioux Falls network, which has 76 links and 24 origin–destination (O–D) pairs. The results of the numerical example indicate that the proposed model can effectively identify the near-optimal solution of the long-term work zone scheduling problem.

Driver injury severity analysis for two work zone types

The aim of this study is to examine whether the effects of factors contributing to the severity of driver injuries vary between long-term and short-term work zones. Multinomial logistic regression analysis is adopted to model the relationship between the influencing factors and drivers' injury and fatality risks. A case study is created using drivers' injury severity data from the NASS general estimate system, and two separate multinomial logistic regression models are developed. By comparing the model results, it is found that the light conditions, day of the week, age, gender, airbag availability, restraint use, vehicle age and most harmful event show homogeneous effects on the drivers' injury and fatality risks in the two work zone types. However, the weather, speed limit, traffic control device and number of lanes exhibit opposing effects on the drivers' injury and fatality risks in the two work zone types.

Micro-simulation of Desired Speed for Temporary Work Zone with a New Calibration Method

Nowadays, the studies of parameter calibration for long-term work zones are limited to driver behaviour and car-following parameters, and no research was found related to calibration of the desired speed distributions during temporary work zones. Obtaining realistic results from simulations of temporary work zones is difficult. Thus, it would be valuable for gaining more valid simulation data if a method of calibrating the desired speed distribution could be applied for traffic simulation model of highway temporary work zones. The calibration method was proposed in five steps: (1) collect and analyse data, (2) plot the travel speed cumulative frequency curves and calibrate the desired speed distribution, (3) conduct simulation runs, (4) validate the simulation results, and (5) propose a new calibration method, which was assessed by T-tests, and the results are very promising. Finally, a simplified calibration method called “Five-Point Method” is presented and the recommended values of five-point are given.

Capacity of Freeway Work Zones in Germany

Work zones considerably influence the traffic flow quality on freeways. In work zones, the capacity can be significantly reduced due to narrower lanes, a reduced number of traffic lanes, and unfavorable roadway geometry. In order to evaluate the impact of work zones on congestion occurrence and resulting delays as well as to allow for a consideration of alternative work zone layouts in the planning process, models to estimate the capacity of work zones are required. The paper presents results from a comprehensive study of work zone capacity on German freeways. In the analysis, a large number of short-term work zones with temporary lane closures as well as long-time work zones with and without a reduction of the number of lanes were covered. Data from loop or radar detectors upstream of the work zones were analyzed. For the capacity estimation of long-term work zones, both deterministic and stochastic approaches were used. In contrast to long-term work zones, traffic flow data measured at short-term work zones include only one traffic breakdown observation in most cases. This breakdown often occurs immediately after the lane closure, which means that the pre-breakdown volume does not represent the capacity of the work zone. Hence, valid capacity estimates could only be determined for the post-breakdown congestion outflow. The estimated capacities were analyzed regarding the influence of the traffic, geometric and control conditions in the work zone. Relevant parameters are the number of lanes, the lane widths, the existence of divided lanes, the existence of a lane reduction as well as the share of commuters and heavy vehicles. For short-time work zones, also the side of the lane closure (left or right lane) has an influence on the capacity. As a result of the study, capacity estimation models for both short- and long-term work zones, which can be applied in work zone planning procedures, are provided.

Traffic Flow Forecasting for Urban Work Zones

None of numerous existing traffic flow forecasting models focus on work zones. Work zone events create conditions that are different from both normal operating conditions and incident conditions. In this paper, four models were developed for forecasting traffic flow for planned work zone events. The four models are random forest, regression tree, multilayer feedforward neural network, and nonparametric regression. Both long-term and short-term traffic flow forecasting applications were investigated. Long-term forecast involves forecasting 24 h in advance using historical traffic data, and short-term forecasts involves forecasting 1 h and 45, 30, and 15 min in advance using real-time temporal and spatial traffic data. Models were evaluated using data from work zone events on two types of roadways, a freeway, i.e., I-270, and a signalized arterial, i.e., MO-141, in St. Louis, MO, USA. The results showed that the random forest model yielded the most accurate long-term and short-term work zone traffic flow forecasts. For freeway data, the most influential variables were the latest interval's look-back traffic flows at the upstream, downstream, and current locations. For arterial data, the most influential variables were the traffic flows from the three look-back intervals at the current location only.

A Tobit model for analyzing speed limit compliance in work zones

Poor compliance with speed limits is a serious safety concern in work zones. Most studies of work zone speeds have focused on descriptive analyses and statistical testing without systematically capturing the effects of vehicle and traffic characteristics. Consequently, little is known about how the characteristics of surrounding traffic and platoons influence speeds. This paper develops a Tobit regression technique for innovatively modeling the probability and the magnitude of non-compliance with speed limits at various locations in work zones. Speed data is transformed into two groups—continuous for non-compliant and left-censored for compliant drivers—to model in a Tobit model framework. The modeling technique is illustrated using speed data from three long-term highway work zones in Queensland, Australia. Consistent and plausible model estimates across the three work zones support the appropriateness and validity of the technique. The results show that the probability and magnitude of speeding was higher for leaders of platoons with larger front gaps, during late afternoon and early morning, when traffic volumes were higher, and when higher proportions of surrounding vehicles were non-compliant. Light vehicles and their followers were also more likely to speed than others. Speeding was more common and greater in magnitude upstream than in the activity area, with higher compliance rates close to the end of the activity area and close to stop/slow traffic controllers. The modeling technique and results have great potential to assist in deployment of appropriate countermeasures by better identifying the traffic characteristics associated with speeding and the locations of lower compliance.

Decision Tree–Based Model for Estimation of Work Zone Capacity

The ability to estimate work zone capacity accurately is imperative because accurate estimates are a key input to estimates of queue length and traffic delay in work zones. This paper aims to develop a decision tree–based model that considers 16 influencing factors to estimate freeway work zone capacity accurately. The F-test splitting criterion and the postpruning approach are employed to grow and prune the decision tree. Freeway work zone capacity data collected from 14 states and cities are used to train, check, and evaluate the decision tree–based capacity estimation model. Statistical comparison results demonstrate that the decision tree–based model outperforms existing short-term and long-term freeway work zone capacity estimation models, especially when the input values of influencing factors are only partially available for the existing models. A comparison with the Highway Capacity Manual (HCM) also indicates that the decision tree–based model can provide a more accurate estimate of freeway work zone capacity. From the decision tree–based model, traffic engineers can easily estimate work zone capacity for a given freeway work zone by tracing a path down the tree to a terminal node. Because of its accuracy and ease of use, the proposed decision tree–based capacity model is a good alternative for traffic engineers to use in estimating freeway work zone capacity. It is expected that the decision tree–based capacity model could be applied to the HCM chapter on freeway facilities.

A probabilistic quantitative risk assessment model for the long-term work zone crashes

Work zones especially long-term work zones increase traffic conflicts and cause safety problems. Proper casualty risk assessment for a work zone is of importance for both traffic safety engineers and travelers. This paper develops a novel probabilistic quantitative risk assessment (QRA) model to evaluate the casualty risk combining frequency and consequence of all accident scenarios triggered by long-term work zone crashes. The casualty risk is measured by the individual risk and societal risk. The individual risk can be interpreted as the frequency of a driver/passenger being killed or injured, and the societal risk describes the relation between frequency and the number of casualties. The proposed probabilistic QRA model consists of the estimation of work zone crash frequency, an event tree and consequence estimation models. There are seven intermediate events – age ( A), crash unit ( CU), vehicle type ( VT), alcohol ( AL), light condition ( LC), crash type ( CT) and severity ( S) – in the event tree. Since the estimated value of probability for some intermediate event may have large uncertainty, the uncertainty can thus be characterized by a random variable. The consequence estimation model takes into account the combination effects of speed and emergency medical service response time ( ERT) on the consequence of work zone crash. Finally, a numerical example based on the Southeast Michigan work zone crash data is carried out. The numerical results show that there will be a 62% decrease of individual fatality risk and 44% reduction of individual injury risk if the mean travel speed is slowed down by 20%. In addition, there will be a 5% reduction of individual fatality risk and 0.05% reduction of individual injury risk if ERT is reduced by 20%. In other words, slowing down speed is more effective than reducing ERT in the casualty risk mitigation.

Methodology for Estimating Operating Speed and Capacity in Work Zones

A new step-by-step methodology for estimation of operating speed and capacity in work zones on highways is presented and validated. The underlying principle of this methodology is that the operating factors in work zones, which include work intensity, lane width, lateral clearance, and other factors, cause motorists to reduce their speed. The reduced speed adversely affects the capacity of the work zones. Video data were collected for around 30 h from 11 work zones on Interstate highways in Illinois where one of the two lanes was closed. These work zones included eight long-term and three short-term ones. Work intensity in the work zone was quantified, and the relationship between work intensity and consequent speed reduction in construction zones was established. Speed reduction in a long-term work zone was established with field data, and the reduction in a short-term work zone was established with data from a driver survey. These relationships were used to compute the operating speed in the work zone. A speed-flow curve, which represents the operating conditions in work zones, was developed. The congested part of the curve was developed with the field data, corresponding to platooning vehicles, and the uncongested part was developed from information in the Highway Capacity Manual and the educated judgment of the authors. Once the operating speed is known, this curve can be used to obtain the capacity of the work zone. The developed methodology was used to predict the operating speed and capacity of work zones, and these predictions were compared with field data for validation.