Highway Work Zones Research Articles

Computation of User Costs at Freeway Work Zones Using Weigh-in-Motion Traffic Data

Consideration of the excess user costs of traffic delays caused by the presence of work zones is essential for assessment of impact of the work zones on the public. The excess user costs include traffic delay costs and additional vehicle operating costs resulting from speed changes at work zones. User costs at highway work zones are increasingly used by highway agencies to determine the contract times of highway construction projects. This paper analyzes the user costs at freeway work zones based on traffic data recorded by weigh-in-motion devices in Indiana. With a high traffic volume, user costs caused by a work zone can be significant; it is therefore desirable to minimize the user costs by expediting construction process. User costs at work zones are often used as the basis of determination of the monetary values for incentive or disincentive clauses in highway contracts for early or late completions of highway construction projects. In this study, the user costs at freeway work zones were computed based on the estimated traffic delays with the weigh-in-motion recorded traffic data.

A refined cellular automaton model to rectify impractical vehicular movement behavior

When implementing cellular automata (CA) into a traffic simulation, one common defect yet to be rectified is the abrupt deceleration when vehicles encounter stationary obstacles or traffic jams. To be more in line with real world vehicular movement, this paper proposes a piecewise-linear movement to replace the conventional particle-hopping movement adopted in most previous CA models. Upon this adjustment and coupled with refined cell system, a new CA model is developed using the rationale of Forbes’ et al. car-following concept. The proposed CA model is validated on a two-lane freeway mainline context. It shows that this model can fix the unrealistic deceleration behaviors, and thus can reflect genuine driver behavior in the real world. The model is also capable of revealing Kerner’s three-phase traffic patterns and phase transitions among them. Furthermore, the proposed CA model is applied to simulate a highway work zone wherein traffic efficiency (maximum flow rates) and safety (speed deviations) impacted by various control schemes are tested.

Lane-Based Dynamic Merge Control Strategy Based on Optimal Thresholds for Highway Work Zone Operations

Despite the potential effectiveness of the dynamic late merge (DLM) control, most existing DLM systems, based on static thresholds, cannot best perform under time-varying traffic conditions. This paper presents an advanced dynamic merge control, called a lane-based dynamic merge control model and its operational algorithm, which is based on the optimized control thresholds that take into account the interactions among the speed, flow, and available work zone capacity. The focus of this study is on how to select the control variables and to determine their optimal thresholds in response to traffic flow dynamics. Evaluation results with extensive simulation experiments have shown the promising properties of the proposed dynamic merge control and its operational algorithm.

A decision support system for selecting the optimal contracting strategy in highway work zone projects

Highway work zone projects are challenging for state highway agencies and contractors as they are often located in urban areas and impact local traffic, business community, and neighborhood leading to a multi-party involvement. There is a dynamic relationship between the involved parties and the performance of any highway work zone project is governed by this dynamic relationship. This paper presents a decision support system to assist state Departments of Transportation in selecting suitable contracting strategies for highway work zone projects by considering, at a macro level, the interrelationships between the stakeholders as well as the critical factors impacting the project. The proposed methodology supplements the current project decision-making process with regard to important project performance variables such as cost, schedule, quality, safety, and public satisfaction.

Estimation of Freeway Work Zone Capacity through Simulation and Field Data

The objective of this research was to develop analytical models and procedures for estimating the capacity of a freeway work zone by considering various geometric-, traffic-, and work zone–related parameters. The study was conducted in two stages: simulation-based modeling and field data collection. In the first stage, CORSIM (Version 5.1) was used to develop a comprehensive database for various work zone scenarios. Analytical models were developed to predict work zone capacity on the basis of these simulated data and previous literature findings considering three work zone configurations: two-to-one, three-to-two, and three-to-one lane closures. In the second stage, field data were collected at a freeway work zone to evaluate and refine the analytical models developed. Data were collected at the freeway work zone site during 15 evening peak periods, which included left- and right-lane closures as well as rainy weather conditions. The observed capacities were compared with those predicted by the new analytical models as well as to those estimated by the Highway Capacity Manual 2000. It was concluded that the analytical models developed predicted within 1% the capacity of the study work zone.

Simulation-Based Study on a Lane-Based Signal System for Merge Control at Freeway Work Zones

This paper presents a new lane-based signal merge (LBSM) control system for freeway work zone operations. The proposed system applies the signal control concept to regulate the vehicles passing the work zone area at a lane-by-lane basis and offers an effective way to maximize the operational efficiency as well as safety. Introduction of the preliminary configuration and principal components associated with the proposed LBSM control contribute the core of this study. To evaluate the effectiveness of the proposed system, this study has also conducted extensive simulation experiments, based on a freeway simulator calibrated with real-world work zone data. The experimental results show that under heavily congested traffic conditions the LBSM can outperform all existing control strategies with respect to the work zone throughput, the average vehicle delay, the average stop delay, and the average number of stops. This study has also investigated critical traffic flow related factors that may impact on the performance of such a system.

Downstream Effects of Speed Photo–Radar Enforcement and Other Speed Reduction Treatments on Work Zones

The effects of automated speed photo–radar enforcement (SPE) and traditional speed reduction treatments (speed feedback trailer, presence of police vehicles with emergency lights on and off, and combinations of the speed feedback trailer and police presence) on speed were studied at a location 1.5 mi downstream of the actual treatment (spatial effects). Three data sets from two Interstate highway work zones were used. Field data consistently showed significant spatial (downstream) effects for SPE. The combination of speed feedback trailer and police vehicle with emergency lights off had downstream effects in some cases but to a lesser degree than SPE. Other treatments showed no significant downstream effects. For free-flowing traffic, SPE reduced the average downstream speed by 2 to 3.8 mph for cars and by 0.8 to 5.3 mph for trucks. Also, SPE reduced speeding cars by 7.1% to 23.4% (except for cars in median in Data Set 1), and speeding trucks by 4.2% to 48.3% (except for trucks in shoulder in Data Set 3). For the general traffic stream, SPE reduced the average downstream speed by 1.1 to 2.9 mph on cars and by 0.9 to 3.3 mph on trucks. When SPE was used, the percentage of speeding cars and trucks in the general traffic stream was reduced by 2.9% to 28.6%, and by 7.5% to 36.1%, respectively. SPE also reduced the percentage of cars in the general traffic stream exceeding the speed limit by more than 10 mph in virtually all cases, and eliminated such trucks in all but one case.

Measurement of Pavement Surface Reflectance for a Balloon Lighting System

Nighttime construction offers many advantages to the public and to state agencies. Under these conditions, traffic is minimal and construction operations can be conducted effectively and quickly. In addition, cooler temperatures are favorable for the equipment and the material being installed. Despite these advantages, controlling glare is a critical and important issue in adequately lighting highway work zones. One of the controlling parameters in glare calculation is the pavement luminance, which is a quantitative measure of the surface brightness. Pavement luminance is based on predefined parameters known as r values provided by the Illuminating Engineering Society of North America (IESNA) for four standard pavement surfaces in the r tables. With the recent introduction of balloon lighting system for construction applications, the objective of this study was to measure pavement reflectance characteristics for this system in the laboratory and to compare the results to the standard r tables. For this purpose, a laboratory experimental setup was developed. On average, measured r values were 20% greater than the IESNA standard values for concrete surfaces (R1), 84% greater for R2 standard surfaces, and 95% greater for R3 standard surfaces. An analysis of variance statistical analysis indicated that the differences between the measured r values and standard r tables were not significant for concrete surfaces but were statistically significant for asphalt road surfaces. This was attributed to the weathering of the road samples used in this study, to the shorter towers used with balloon lights, and to major changes in asphalt construction practices and mix ingredients in the past 30 years. Recommendations based on the results of this study are presented.

Effectiveness of temporary traffic control measures in highway work zones

In the United States, hundreds of people lose their lives each year and many more are injured due to vehicle crashes in the work zones. Over the years, temporary traffic control (TCC) measures have been developed and deployed in work zones. To continuously improve the safety, there is a need to identify the traffic control deficiencies in work zones by evaluating the effectiveness of existing TTC measures based on the real crash cases. In this study, researchers evaluated the effectiveness of several commonly used TTC methods using logistic regression techniques and various significance test methods including likelihood ratio test, score test, and Wald test. These TTC methods included flagger/officer, stop sign/signal, flasher, no passing zone control, and pavement center/edge lines. A total of 655 severe crashes in Kansas highway work zones between January 2003 and December 2004 were used for the evaluation, which included 29 fatal crashes and 626 injury crashes. Results indicated that flagger, flasher, and pavement center/edge lines were effective in reducing the probability of causing fatalities when severe crashes occurred. In addition, using these devices could prevent some common human errors, such as “disregarded traffic control”, “inattentive driving”, “followed too closely”, and “exceeded speed limit or too fast for condition”, from causing severe crashes.

Development of crash-severity-index models for the measurement of work zone risk levels

Highway work zones interrupt regular traffic flows and create safety problems. Improving safety without sacrificing the main function of highways is a challenging task that traffic engineers and researchers have to confront. In this study, the concept of using crash severity index (CSI) for work zone safety evaluation was proposed and a set of CSI models were developed through the modeling of work zone crash severity outcomes. A CSI is a numerical value between zero and one that is estimated from given work zone variables. It is interpreted as the likelihood of having fatality/fatalities when a severe crash occurs in a given work zone. The CSI models were developed using a three-step approach. First, a wide range of crash variables were examined in a comprehensive manner and the significant risk factors that had impact on crash severity were selected. Second, the CSI models were developed using logistic regression technique by incorporating the selected risk factors. Finally, the developed models were validated using the recent crash data and their ability in assessing work zone risk levels were analyzed. Results of this study showed that CSI models can provide straightforward measurements of work zone risk levels.

Evaluation of Messages on Changeable Message Signs as a Speed Control Measure in Highway Work Zones

The objective of this study is to measure the effectiveness of three commonly used changeable message sign (CMS) messages in reducing vehicular speeds and variances in highway work zones. This paper presents the results of a field study conducted on Interstate-90 in western New York State to evaluate the use of three different types of messages displayed on a CMS, as a speed control measure. The study included speed measurements of nearly 180,000 vehicles. The three types of CMS messages tested were: (1) RIGHT∣LANE∣CLOSED∼KEEP∣LEFT; (2) WORKZONE∣MAXSPEED∣45MPH∼BE∣PREPARED∣TOSTOP; and (3) LEFT∣LANE∣CLOSED∼KEEP∣RIGHT. Of the three CMS messages tested, the CMS message stating “WORKZONE∣MAXSPEED∣45MPH∼BE∣PREPARED∣TOSTOP” proved the most effective, significantly reducing vehicle speeds by 3.3–6.7mi∕h(5.3–10.8km∕h). The other two CMS messages were not as effective. The standard deviation of speed for the CMS message: WORKZONE∣MAXSPEED∣45MPH∼BE∣PREPARED∣TOSTOP increased by 1.1–1.7mi∕h(1.8–2.7km∕h) in the driving lane and 0.2–2.0mi∕h(0.3–3.2km∕h) in the passing lane. The speed variances for the other two CMS messages ranged from −2.00to1.13mi∕h (from −3.23km∕hto1.83km∕h).

Methodology for Computing Delay and User Costs in Work Zones

A step-by-step methodology for computing delays and user costs in highway work zones is presented in this paper. The methodology is based on the relationship between speed and capacity in work zones. Speed is adjusted to account for the adverse effects of roadway geometrics, work intensity, speed enforcement, and other work zone factors. Speed reductions for work intensity and narrow lane widths were determined previously by use of data from work zones. Values from the Highway Capacity Manual were used where data from work zones were not available. The fundamental difference between this methodology and previous approaches is that it accounts for the various work zone factors. Two applications of the methodology are presented, one with queuing and one without queuing, to real-world work zones. Results are compared with field data. For the nonqueuing site, the computed speed and capacity were 44.4 mph and 1,778 vehicles per hour per lane (vphpl), respectively, while the field speed and capacity were 44 mph and 1,708 vphpl, respectively. For the queuing site, computed capacity was 1,012 vphpl while the field capacity was 1,220 vphpl. Considering the assumptions made in the methodology for some of the parameters, these results build confidence in the methodology. Extensive validation of this methodology is strongly recommended.

Dynamic Late Lane Merge System at Freeway Construction Work Zones

In normal work zones with lane closures, drivers do not merge at any one definite point, a situation thus often causing a sudden interruption in traffic flow and sometimes higher delay and longer queue. The Dynamic Late Lane Merge System (DLLMS) is used to specify a definite merge point, improve the flow of congested work zones, and reduce queue lengths in travel lanes. The DLLMS was implemented in Michigan on three freeway segments that were reduced from two lanes to one lane because of highway construction work zones. The DLLMS directed traffic to use both lanes (open and closed lanes) until the designated “merge point” (close to the taper) where traffic from each lane was instructed to take turns merging into the open lane. On the basis of travel time characteristics, merge locations, and throughput, the effectiveness of the DLLMS was evaluated as a part of this study. The before period data were not available; therefore, a conventional work zone merge system, located on eastbound I-94, was used as a control site for the westbound I-94 test site. Comparison of the I-94 control and test sites indicated that the presence of the DLLMS improved the flow of travel and increased the percentage of vehicles that merged at or near the designated taper location. Based on the expected travel time savings, at a $5/h value of time, the benefit-cost ratio will be greater than 1, indicating that the monetary benefits of the DLLMS outweigh the cost of the system.

Algorithm for the Planning of Optimum Highway Work Zones

Work zones often cause traffic congestion on high volume roads. As traffic volumes increase so does work zone-related traffic congestion and so does the public demand for road agencies to decrease both their number and duration. Negative impacts on road users can be minimized by bundling interventions on several interconnected road sections instead of treating each road section separately. Negative impacts on road users can be quantified in user costs. The optimum work zone is the one that results in the minimum overall agency and user costs. The minimization of these costs is often the goal of corridor planning. In order to achieve this goal the interventions on each asset type (pavement, bridges, tunnels, hardware, etc.) must be bundled into optimum packages. In this paper a method is presented that enables road agencies to determine optimum work zones and intervention packages. The method allows the consideration of both budget constraints and distance constraints, including maximum permissible work zone length or minimum distance between work zones. The mathematical formulation of this optimization problem is a binary program that can be solved by existing techniques (i.e., the branch-and-bound method). The feasibility of the approach is illustrated with a simple example.

Driving Simulator Validation for Nighttime Construction Work Zone Devices

Research was conducted to ascertain the validity of a driving simulator in determining the effectiveness of temporary traffic control devices in a work zone at night. The research was conducted through a field study and a simulator study. The field study examined speeds at six sites. The simulator study involved 127 human subjects. Spot speeds were observed at three locations in a freeway work zone. Locations of the speed studies were at the beginning of the work zone near the transition area, in the middle of the work zone, and at the end of the work zone near the downstream taper. Statistical analyses were conducted to determine whether participants of the study performed differently in the simulator, compared with in the field. Research results established that because of the motorist's perceived risk of work zones, driving simulators may not replicate mean speeds observed in the field.

Seemingly Unrelated Regression Model of Car Speeds and Speed Deviations in Freeway Work Zones

Current work zone design and traffic control guidance is based heavily on desirable speed-related outcomes, but knowledge concerning actual speed-related outcomes of design and traffic control decisions is limited. The objective of this research is to investigate relationships between speed behavior, roadway and roadside geometrics, and traffic control in work zones. The objective is accomplished through specification and estimation of a seemingly unrelated regression (SUR) model. The dependent variables modeled were 85th-percentile passenger car speed and standard deviation of passenger car speed. Work zone design and traffic control features were investigated as explanatory variables. Speed and infrastructure data used for estimation were collected in Pennsylvania and Texas work zones. The SUR model accounted for contemporaneous correlations of the disturbance terms in the two speed equations. In the equation for 85th-percentile speed, regression parameters were statistically significant for variables representing work zone configuration, type of roadway infrastructure, work zone location, distance traveled from the beginning of the work zone, posted speed limit, vertical alignment, and total paved cross-section width. In the equation for standard deviation of speed, parameters were statistically significant for variables representing distance traveled from the beginning of the work zone, total paved cross-section width, and reduction in posted speed and roadside conditions. Several recommendations for future work are provided, including expansion of the system of equations to include 85th-percentile truck speeds and standard deviation of truck speeds and consideration of possible contemporaneous relationships between speed measures.

Evaluation of Alternative Dates for Advance Notification on Portable Changeable Message Signs in Work Zones

Results of a laptop-based human factors study of alternative formats of presenting notice of future roadwork messages on portable changeable message signs (PCMS) in highway work zones are documented. A total of 192 participants across Texas were shown a series of different two-phase messages for a fixed period of time and asked questions by test administrators to determine comprehension and recall of the information presented in each message. Participants were also asked to indicate their preferred format for presenting such information on a PCMS. On the basis of these studies, it is recommended that messages that require the display of calendar dates for future roadwork and other traffic control activities use a message format consisting of the three-character abbreviation of the month (e.g., APR for April) in conjunction with the date. When future work activities span several days in the same month, the month needs to be noted only once in the message (i.e., APR 21–23) rather than repeating the month (i.e., APR 21-APR 23).

Intelligent infrastructure-based queue-end warning system for avoiding rear impacts

Accident avoidance is a very important part of enhancing road safety. The development of a queue-end warning system for highway work zones which automatically predicts queue-end location and alerts drivers so that rear-end collisions can be avoided has been described. In the absence of the widespread use of in-vehicle collision warning devices, dynamic messages about queue-end, displayed on portable variable message sign (PVMS) boards, are necessary for improving road safety. Although queues at selected locations along the road can be detected by the simple use of sensors, the changing nature of queue length would require numerous sensors to find the end of traffic queue. The reported queue-end warning system is based on a combination of sensors for detecting traffic and an artificial neural network (ANN) model-based algorithm for predicting queue-end location and issuing warning messages displayed on PVMS. Following the characterisation of work zones in terms of functional areas and geometrics, a microsimulator was calibrated and validated. Simulations were carried out next with traffic sensors and queue counter looped-in and the resulting data were used for training and validation of ANN models for queue length prediction. An automated information system was synthesised that integrates traffic sensors, ANN models, PVMS and potential links with other media. Selected results of ANN models illustrate their application in the queue-end warning system.

Fatal accidents in nighttime vs. daytime highway construction work zones

Introduction Awareness about worker safety in nighttime construction has been a major concern because it is believed that nighttime construction creates hazardous work conditions. However, only a few studies provide valuable comparative information about accident characteristics of nighttime and daytime highway construction activities. Method This study investigates fatal accidents that occurred in Illinois highway work zones in the period 1996–2001 in order to determine the safety differences between nighttime and daytime highway construction. The lighting and weather conditions were included into the study as control parameters to see their effects on the frequency of fatal accidents occurring in work zones. Results According to this study, there is evidence that nighttime construction is more hazardous than daytime construction. The inclusion of a weather parameter into the analysis has limited effect on this finding. Impact on Industry The study justifies establishing an efficient work zone accident reporting system and taking all necessary measures to enhance safety in nighttime work zones.

Validation of a Model for Predicting Schedule Changes in Highway Work Zones—Case Studies

There are currently no standard or accepted methods in the construction industry to calculate the probable impact of indirect cost factors on the schedule of highway work zone projects. This paper presents a model for stochastic analysis of factors affecting construction schedule in highway work zones and determination of probable changes, i.e., reduction or escalation, in the original estimated schedule for a given project. Also, three case studies from the Indiana Department of Transportation are illustrated in this paper in order to show the applicability of the model as a forecasting tool for predicting schedule changes on state Department of Transportation projects.