Interstate Work Zones Research Articles

Using Anonymous Connected Vehicle Data to Evaluate Impact of Speed Feedback Displays, Speed Limit Signs and Roadway Features on Interstate Work Zones Speeds

Annually, there are over 120,000 crashes in work zones in the United States. High speeds in construction zones are a well-documented risk factor that increases the frequency and severity of crashes. This study used connected vehicle data to evaluate the spatial and temporal impact that regulatory signs, speed feedback displays, and construction site geometry had on vehicle speed. Over 27,000 unique trips over 2 weeks on a 15-mile interstate construction work zone near Lebanon, IN were analyzed. Spatial analysis over a 0.2-mi segment before and after the posted speed limit signs showed that the regulatory signs had no statistical impact on reducing speeds. A before/after analysis was also conducted to study the impact of radar-based speed feedback that displays the motorists’ speed on a sign below a regulatory speed limit sign. Results showed a maximum drop in median speeds of approximately 5 mph. Speeds greater than 15 mph above the speed limit dropped by 10% - 15%. The reduction in speeds began approximately 1000 feet ahead of the sign and results were found to be statistically significant. The analysis also revealed that larger speed drops inside the work zone were due to geometric constraints that required additional driver workloads, especially during shoulder width changes and lane shifts. The results from this study will be helpful for agencies to understand driver behavior in the work zones and to identify proper speed limit compliance techniques that significantly reduce driver speeds in and around work zones.

Correlating Hard-Braking Activity with Crash Occurrences on Interstate Construction Projects in Indiana

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.

Upgrading the FHWA Work Zone Model Version 2.0 and Validating Its Performance along I-91 in Springfield, Massachusetts

Freeway work zones can have significant safety and operational impacts. To mitigate these, planners and engineers rely on accurate simulation tools to assess various work zone design and scheduling alternatives. Microsimulation models are often used to predict traffic conditions along freeways, however, they were not created to replicate car-following through work zones and therefore cannot be used to accurately predict work zone impacts. So that practitioners can use microsimulation to better predict work zone impacts, FHWA created the Work Zone Driver Model v1.0 (FHWA v1.0) software that overrides car-following in commercial microsimulation software packages for work zone segments. FHWA v1.0 was tested in a 2017 case study. Results showed acceptable performance, however, there were opportunities to improve the software’s usability and accuracy. Findings were used to upgrade the software and create the FHWA Work Zone Driver Model v2.0 (FHWA v2.0). This paper demonstrates the enhanced capabilities of FHWA v2.0 by interfacing with VISSIM and recreating the 2017 case study, testing its performance along the same interstate work zone in Springfield, MA. FHWA v2.0’s performance was compared with field data, with Wiedemann 99 (W99), and with FHWA v1.0. Performance metrics were selected to align with state departments of transportation (DOTs) work zone management efforts. Results show improved performance from FHWA v2.0 as it predicted queue lengths, queue locations, and travel speeds more accurately than FHWA v1.0 and W99. The enhanced software also addressed some of the variability and merging issues described in the 2017 case study. Next steps are described.

Evaluation of Interstate Work Zone Mobility using Probe Vehicle Data and Machine Learning Techniques

According to the Federal Highway Administration (FHWA), US work zones on freeways account for nearly 24% of nonrecurring freeway delays and 10% of overall congestion. Historically, there have been limited scalable datasets to investigate the specific causes of congestion due to work zones or to improve work zone planning processes to characterize the impact of work zone congestion. In recent years, third-party data vendors have provided scalable speed data from Global Positioning System (GPS) devices and cell phones which can be used to characterize mobility on all roadways. Each work zone has unique characteristics and varying mobility impacts which are predicted during the planning and design phases, but can realistically be quite different from what is ultimately experienced by the traveling public. This paper uses these datasets to introduce a scalable Work Zone Mobility Audit (WZMA) template. Additionally, the paper uses metrics developed for individual work zones to characterize the impact of more than 250 work zones varying in length and duration from Southeast Michigan. The authors make recommendations to work zone engineers on useful data to collect for improving the WZMA. As more systematic work zone data are collected, improved analytical assessment techniques, such as machine learning processes, can be used to identify the factors that will predict future work zone impacts. The paper concludes by demonstrating two machine learning algorithms, Random Forest and XGBoost, which show historical speed variation is a critical component when predicting the mobility impact of work zones.

Dashboards for Monitoring Congestion and Crashes in Interstate Work Zones

Work zones present challenges to safety and mobility that require agencies to balance limited resources with vital traffic management activities. Extensive literature exists regarding the impact of congestion and recommendations for work zone design to provide safe and efficient traffic operations. However, it is often infeasible or unsafe to inspect every work zone within an agency’s jurisdiction, so it is important to obtain operational feedback regarding congestion and crashes in work zones to prioritize inspection activities. This paper outlines the use of connected vehicle speed data and crash report data to identify operational performance problems in work zones. This is a way to provide feedback to queuing models used to design maintenance-of-traffic (MOT) plans. A weekly work zone report and dashboards were developed for use by the Indiana Department of Transportation (INDOT) for the purpose of assessing and improving both mobility and safety in work zones. The study has developed a mile-hours of congestion graph, frequency of speed delta heat map, congestion profile graph, and the Route Builder interactive application to comprehensively visualize work zone performance. This weekly report provides a mechanism for agency staff to maintain situational awareness of which work zones were most challenging for queues and during what periods those were likely to occur. In one case study, the reports were used to identify and mitigate operational performance problems in a work zone within 4 weeks, reducing congestion and crash rates. The integration of these data provided project managers with quantitative information about traffic mobility and performance of work zones for informed decision-making during the construction season.

Validating the Performance of the FHWA Work Zone Model Version 1.0: A Case Study along I-91 in Springfield, Massachusetts

Central to the effective design of work zones is being able to understand how drivers behave as they approach and enter a work zone area. States use simulation tools in modeling freeway work zones to predict work zone impacts and to select optimal design and deployment strategies. While simple and complex microscopic models have been used over the years to analyze driver behavior, most models were not designed for application in work zones. Using data collected from an instrumented research vehicle and model components from two PhD dissertations, FHWA created the Work Zone Driver Model and programed the Work Zone Driver Model DLL v1.0, a software that could override car-following in commercial microsimulation software packages so that practitioners can better predict work zone impacts. This paper demonstrates the capabilities of the FHWA Work Zone Driver Model DLL v1.0, interfaced with VISSIM and tested on an Interstate work zone in Springfield, Massachusetts. The dynamic link library’s (DLL’s) performance is compared with field data collected using an instrumented research vehicle and to Weidemann 99 in VISSIM. Performance metrics were selected to align with state department of transportation work zone management efforts. Results showed acceptable performance from the DLL, as it predicted queue locations and travel speeds that were near field observations. Limitations of the DLL and interface are discussed, and opportunities for improving version 2.0 are described.

Evaluation of Merge Control Strategies at Interstate Work Zones under Peak and Off-Peak Traffic Conditions

Maintenance and rehabilitation projects of interstate facilities typically mandate lane closures. Lane closures require merging maneuvers that often result in reduced speeds and traffic bottlenecks. Work zone impacts on traffic operations are magnified when project durations are extended. Conventionally, work zone traffic control plans are developed to address work zone impacts. This study evaluated various merge control strategies at interstate work zones peak and off-peak traffic conditions and summarized related impacts. A comprehensive microscopic simulation model was developed in full consideration of driver/vehicle behavior at work zones. The analysis of simulation results revealed that merge control strategies, when implemented during peak and off-peak conditions, can preserve the level of service and provide favorable mobility, safety, and environmental impacts. In addition, results indicate that transportation agencies’ practice of scheduling work zone activities during the off-peak may not be the most optimum approach. Overall, the findings of this study highlight the need for evaluation of work zone scheduling practices in full consideration of agency, user, and project costs.

Speed limit effectiveness in short-term rural interstate work zones

Average speed and speed variance are two characteristics of traffic flow that affect accident rates and severity near work zones. Operationally, work zones account for approximately 24% of the non-recurring delay. A policy for work zone speed limits has to delicately balance the safety and the efficiency impacts. If speeds are set too low, then avoidable congestion and speed violations might result. If speeds are set too high then, again, safety may be compromised. In this paper, results from field studies conducted on three Interstate 70 maintenance short-term work zones in rural Missouri are presented for three different speed limit scenarios: no posted speed limit reduction, 10 mph posted speed limit reduction, and 20 mph posted speed limit reduction. The 85th percentile speeds and standard deviation of speed were found to be 81 and 10 mph; 62 and 8 mph; and 48 and 6 mph, respectively for the three scenarios. The differences in 85th percentile speed and standard deviation of speed among all three scenarios were statistically significant. The per cent of drivers who exceed speed limit by over 10 mph were 15·4, 4·8, and 0·9%, respectively. Thus a reduction in posted speed limit was effective in reducing prevailing speeds and speed variances in short-term work zones in rural Missouri.

Estimating Interstate Highway Capacity for Short-Term Work Zone Lane Closures

Defining and understanding traffic flow parameters within short-term Interstate work zones are crucial in developing effective policies to manage construction and maintenance work conducted on the nation's heavily traveled freeways. The South Carolina Department of Transportation (DOT) initiated a research study to develop a methodology for use in determining an updated lane closure policy for Interstate highway work zones. Phase 1 of the research was completed in May 2003, and findings identified threshold volumes for two-to-one lane closure work zone configurations. Phase 2 of the research further expanded numerically derived relationships and contained analysis of other short-term lane closure configurations including three-to-two and three-to-one lane closures. Both research phases concentrated on methods to determine the number of vehicles per lane per hour that can pass through short-term Interstate work zone lane closures with minimum or acceptable levels of delay as defined by South Carolina DOT. Phase 2 includes an expanded list of data collection sites with differing work zone characteristics. This paper presents the analysis and results of Phase 2 of the research. Headway analysis revealed that passenger car equivalents (PCEs) differed for various speed ranges and modified PCEs for various speed groups were applied in calculating capacity. A model for calculating work zone capacity that incorporates base capacity, PCEs for various speed groups, adjustment factors related to specific work zone characteristics, and number of lanes open through the work zone, is recommended.

Estimating Interstate Highway Capacity for Short-Term Work Zone Lane Closures: Development of Methodology

Defining and understanding traffic flow parameters within short-term Interstate work zones are crucial in developing effective policies to manage construction and maintenance work conducted on the nation's heavily traveled freeways. The South Carolina Department of Transportation (DOT) initiated a research study to develop a methodology for use in determining an updated lane closure policy for Interstate highway work zones. Phase 1 of the research was completed in May 2003, and findings identified threshold volumes for two-to-one lane closure work zone configurations. Phase 2 of the research further expanded numerically derived relationships and contained analysis of other short-term lane closure configurations including three-to-two and three-to-one lane closures. Both research phases concentrated on methods to determine the number of vehicles per lane per hour that can pass through short-term Interstate work zone lane closures with minimum or acceptable levels of delay as defined by South Carolina DOT. ...

Evaluation of Interstate Highway Capacity for Short-Term Work Zone Lane Closures

The need to maintain adequate traffic flow through short-term Interstate work zones is paramount on today's heavily traveled freeways. Numerous states have policies related to traffic flow thresholds, vehicle delay, and vehicle queue lengths that provide guidance on conditions when shortterm lane closures can be instituted. Generally, traffic flow threshold limits are a function of traffic-stream characteristics, highway geometry, work zone location, type of construction activities, and work zone configuration. A research study was initiated in South Carolina to examine quantitatively the development and implementation of a methodology for use in determining an updated lane-closure policy based on statespecific parameters. The study focused on determining the number of vehicles per lane per hour that can pass through short-term Interstate work zone lane closures with minimal or acceptable levels of delay. Research tasks included a survey of policies of other states, field-data collection, and methodology development. A methodology was developed with field data collected from 22 work zone sites along South Carolina's Interstate system. Data were obtained during a 12-month period from September 2001 to August 2002. Data collection procedures and data analysis methods employed in model development are summarized. Results of this study may be helpful to state highway agencies interested in developing similar research-based policy guidelines for short-term Interstate lane closures in their jurisdictions.

Analysis of Crash Rates at Interstate Work Zones in Indiana

The aging Interstate system in the United States requires extensive rehabilitation and maintenance, which results in the closure of a significant portion of the system each year to accommodate work zones. These work zones not only cause travel delay, they also create safety hazards. An analysis of crash rates at Interstate work zones in Indiana is presented. Crash rates in work zones were found to be higher than those on comparable highway sections without work zones. It is believed that lane closure strategies also may influence crash potential at work zones. An analysis of the relative safety effects of two commonly used lane closure strategies, partial lane closure and crossover, is presented.

Analysis of Crash Rates at Interstate Work Zones in Indiana

The aging Interstate system in the United States requires extensive rehabilitation and maintenance, which results in the closure of a significant portion of the system each year to accommodate work zones. These work zones not only cause travel delay, they also create safety hazards. An analysis of crash rates at Interstate work zones in Indiana is presented. Crash rates in work zones were found to be higher than those on comparable highway sections without work zones. It is believed that lane closure strategies also may influence crash potential at work zones. An analysis of the relative safety effects of two commonly used lane closure strategies, partial lane closure and crossover, is presented.

Evaluation of Crossover and Partial Lane Closure Strategies for Interstate Work Zones in Indiana

There are two main lane closure strategies for Interstate highway work zones, crossover and partial lane closure. Depending on the situation one or the other strategy may be more desirable. However, little research has been done to develop a systematic method for selecting appropriate lane closure strategies. The selection of appropriate lane closure strategies at Interstate highway work zones is discussed.

Evaluation of Crossover and Partial Lane Closure Strategies for Interstate Work Zones in Indiana

There are two main lane closure strategies for Interstate highway work zones, crossover and partial lane closure. Depending on the situation one or the other strategy may be more desirable. However, little research has been done to develop a systematic method for selecting appropriate lane closure strategies. The selection of appropriate lane closure strategies at Interstate highway work zones is discussed.