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Project Details
STATUS

In-Progress

PROJECT NUMBER

24-887, TPF-5(438)--72-00

START DATE

03/01/24

END DATE

05/31/25

SPONSORS

Iowa Department of Transportation
Smart Work Zone Deployment Initiative

Researchers
Principal Investigator
Guillermo Basulto-Elias

Research Scientist, CTRE

Co-Principal Investigator
Skylar Knickerbocker

Research Scientist, CTRE

About the research

The research team aims to create an analytical tool for work zones by identifying essential performance indicators and measurements. To achieve this, a thorough literature review will be conducted, consolidating prior research and state-level initiatives that relate to work zone performance. Based on the findings, the team will develop a comprehensive list of performance metrics and summarize the results in a document. Finally, these key measurements and performance indicators will be used to create an analytical tool for work zones that presents performance data in easy-to-read tables, diagrams, and downloadable reports. This will generate performance analyses after stakeholders upload or link their data sources.

Project Details
STATUS

Completed

PROJECT NUMBER

20-733, TPF-5(438)

START DATE

01/01/21

END DATE

03/08/24

FOCUS AREAS

Safety

RESEARCH CENTERS InTrans, SWZDI
SPONSORS

Iowa Department of Transportation
Smart Work Zone Deployment Initiative

Researchers
Principal Investigator
Timothy Gates
Co-Principal Investigator
Peter Savolainen
Co-Principal Investigator
Praveen Edara
Co-Principal Investigator
Henry Brown

About the research

This study investigated methods for improving the effectiveness of speed feedback trailers (SFTs) when used as a speed management strategy in highway work zones. The research included a literature review, a state department of transportation (DOT) survey, and field evaluations conducted at several freeway work zones. The findings were synthesized to provide recommendations on methods for optimizing the deployment of SFT in freeway work zones. The state DOT survey revealed that SFTs are widely implemented in work zones across the United States, most commonly for lane closures and traffic shifts. Their use varies across states, ranging from optional to mandatory under specific conditions. SFTs are most commonly positioned near the work area or in advance of the lane closure taper and are often relocated as the work progresses. From there, a series of field studies were conducted within freeway work zones in Michigan and Missouri to evaluate the effectiveness of various SFT deployment strategies towards reducing work zone speeds and improving speed compliance. These evaluations, conducted in multiple phases and at five freeway work zone locations, sought to yield insights and recommendations for optimizing SFT deployment and introducing measures to improve their overall effectiveness. The evaluations specifically assessed the impact of strategically placing SFTs at various locations within the work zones, including near the start of a lane closure, approaching a work area, approaching a lane shift, and within a freeway crossover. Additionally, the effectiveness of SFTs were also assessed when combined with other strategies, like digital speed limits (DSLs) signs and police vehicle presence within the work zone. Although SFTs were generally effective at reducing work zone speeds regardless of the deployment characteristics, they tended to be more effective when positioned closer to the work area, including ingress/egress locations, where speeds were up to 3.6 mph lower when the SFT was present and active. SFTs were also effective at lowering work zone speeds when positioned within 1,000 beyond the end of the lane closure taper, within 1,000 ft in advance of the start of the taper, and within freeway crossovers. The speed reduction effects were generally sustained for at least one-half mile beyond the SFT. SFTs were also found to improve speed reductions measured near a police vehicle positioned within the lane closure by an additional 1.4 mph. Additionally, when paired with DSL signs on the same trailer assembly, the speed feedback display reduced speeds near the work area by an additional 1.8 mph. It is recommended that if only a single SFT is to be used, it should be positioned near the work area, approximately 200 ft in advance of the active work. If additional SFTs are available, then it is recommended that one be positioned within 1,000 ft upstream of the lane closure, shift, or crossover. Additionally, an SFT should be placed shortly beyond the end (e.g., within 1,000 ft) of any lane closure taper, preferably adjacent to the initial speed limit sign.

Project Details
STATUS

In-Progress

PROJECT NUMBER

23-839, TPF-5(438)

START DATE

03/01/23

END DATE

06/30/24

SPONSORS

Iowa Department of Transportation
Smart Work Zone Deployment Initiative

Researchers
Principal Investigator
Skylar Knickerbocker

Research Scientist, CTRE

About the research

Improving the accuracy of work zone data is a multi-layered problem of which a number of agencies have been working to address over the last several years. Connected temporary traffic control devices (cTTCDs) such as smart arrow boards and other connected devices have the capabilities to improve the accuracy of work zone data without a contractor or agency employee having to manually enter the information. As the number and types of devices have increased, little guidance has been developed on how to use information from these devices within an agency. This project will document and evaluate how cTTCDs can be used by an agency for both historical and real-time applications. The approach starts with an agency state-of-the-practice review to summarize how the data are currently being utilized. A number of integration methods will be evaluated with the goal of highlighting noteworthy practices and documenting agency considerations when integrating the data into their systems.

Project Details
STATUS

In-Progress

PROJECT NUMBER

23-834, TPF-5(438)

START DATE

03/01/23

END DATE

02/29/24

SPONSORS

Iowa Department of Transportation
Smart Work Zone Deployment Initiative

Researchers
Principal Investigator
Christopher Day

Research Scientist, CTRE

Co-Principal Investigator
Skylar Knickerbocker

Research Scientist, CTRE

About the research

Recent advances in data collection technologies have made it increasingly possible to monitor traffic conditions with increasing levels of detail, facilitating the task of providing advance warning of work zone conditions to the traveling public. Today, a variety of such technologies exist, including automated vehicle identification (e.g., Bluetooth), automatic vehicle location (AVL) (e.g., average segment speeds), and trajectory data from connected vehicles. Different data sources provide different types of information, have different latency, varying spatial and temporal resolutions, and different requirements for use. There is a need to gather and synthesize available information about the effectiveness and limitations of alternative data sources for the application of real-time work zone monitoring and communicating information to the public. The possibility of integrating multiple data sources for monitoring and public information uses also needs to be investigated.

Project Details
STATUS

Completed

PROJECT NUMBER

20-733, TPF-5(438)

START DATE

01/01/21

END DATE

10/28/22

FOCUS AREAS

Safety

RESEARCH CENTERS InTrans, SWZDI
SPONSORS

Smart Work Zone Deployment Initiative

Researchers
Principal Investigator
Peter Savolainen
Co-Principal Investigator
Timothy Gates
Co-Principal Investigator
Praveen Edara
Co-Principal Investigator
Henry Brown

About the research

This study sought to identify best practices for setting work zone speed limits by state departments of transportation (DOTs) and to evaluate select strategies for improving compliance with work zone speed limits. This was achieved by synthesizing information from a literature review, a state DOT survey, and field evaluations of select speed management strategies.

The state DOT survey found that work zone speed limits are typically established based on the characteristics and conditions of the site, including permanent speed limit, facility type, worker presence, positive protection, work duration, and type and location of work activity.

Work zone speed limit reductions of 10 mph are most frequently utilized on high-speed facility types, with further reductions provided based on worker presence in the absence of positive protection. While the 10 mph speed limit reduction is often viewed as effective, the use of a 45 mph work zone speed limit when workers are present may require the use of additional speed reduction countermeasures to be effective.

Research studies have generally shown several types of work zone speed management strategies, such as speed display signs, law enforcement, variable (dynamic) speed limits, temporary rumble strips, and portable changeable message sign (PCMS) messages, to be effective in reducing vehicle speeds in work zones.

The work zone speed management strategies most frequently implemented by state DOTs include higher fines for speeding in work zones and lights on contractor or maintenance vehicles. While DOTs generally view law enforcement with an officer present as the most effective strategy for managing work zone speeds, they also perceive the availability of law enforcement as the greatest challenge to managing work zone speeds, followed by driver indifference and distracted drivers.

Based on the findings from the literature review and DOT survey, a field study was performed to assess the effectiveness of two work zone speed management strategies, which included a speed feedback trailer (SFT) and law enforcement. In general, the magnitude of the speed reduction effects were greatest in the general proximity of the SFT. Accordingly, positioning the SFT near the end of the taper led to lower speeds for a more sustained distance into the work zone compared to when the SFT was positioned near the start of the taper.

A second field evaluation assessed the effectiveness of a specialized work zone enforcement strategy that included a covert speed measurement vehicle positioned near the end of the work zone along with four police cars positioned just beyond the end of the work zone to stop speeding drivers. The visible presence of law enforcement activities at this location reduced work zone speeds by approximately 5 to 7 mph.

Project Details
STATUS

Completed

PROJECT NUMBER

20-733, TPF-5(438)

START DATE

07/01/20

END DATE

01/21/22

FOCUS AREAS

Safety

RESEARCH CENTERS InTrans, SWZDI
SPONSORS

Smart Work Zone Deployment Initiative

Researchers
Principal Investigator
Timothy Gates
Co-Principal Investigator
Peter Savolainen

About the research

Work zones that include a single lane closure on a two-lane, two-way roadway present unique traffic control challenges. In these situations, traffic regulators (i.e., flaggers or temporary traffic signals) are often utilized to regulate traffic such that only a single direction utilizes the open travel lane at any time. Recently, an experimental traffic control treatment, referred to as the driveway assistance device (DAD), was developed to help drivers safely enter a one-lane, bi-directional work zone from a driveway or minor side street by using alternating left and right flashing arrows along with a steady red indication. As the DAD is a relatively new and under-researched treatment, much is still unknown about the optimal designs of the signal display and auxiliary signage to provide the highest comprehension and compliance.

To address these issues, research was performed to determine best practices related to the DAD design and to develop guidelines related to the use of DADs in one-lane, bi-directional work zones. First, a nationwide online survey of drivers was conducted to determine the DAD signal configurations and auxiliary sign messages that elicited the highest rates of compliance or most effectively communicated the proper driver action. The survey was supplemented by a field study performed in northern Michigan that evaluated the effects of five different auxiliary signs on driver compliance when utilized with a DAD. The conclusions and recommendations resulting from these efforts are summarized as follows. The auxiliary signs most effectively conveyed the proper driver action if the message included the word “Turn” as opposed to “Yield” and if a No Turn on Red Sign was included. Additional improvements were observed for signs that included a prominent “WAIT” message at the top of the sign. These findings were consistent between the survey and field study. Turning to the characteristics of the DAD signal indication, compared to yellow flashing arrows, red flashing arrows showed far fewer “Turn at any time” survey responses, although yellow flashing arrows showed considerably less uncertainty as to the proper action for drivers. Considering the DAD signal head configuration, the horizontal and doghouse configurations more effectively conveyed the proper driver action compared to the red-over-yellow arrows configuration in the driver survey. Based on the research findings, DADs are recommended for continued experimental use along with appropriate auxiliary signage at work zones that include one-lane, two-way traffic where it is not practical or feasible to provide a continuous flagger or temporary traffic signal operation.

Project Details
STATUS

Completed

PROJECT NUMBER

18-646

START DATE

01/01/19

END DATE

12/31/21

SPONSORS

Smart Work Zone Deployment Initiative

Researchers
Principal Investigator
Carlos Sun
Co-Principal Investigator
Praveen Edara
Co-Principal Investigator
Yaw Adu-Gyamfi

About the research

It is anticipated that autonomous truck platooning could lead to many benefits, such as maximizing existing road capacity, decreasing fuel consumption through drafting, and reducing emissions. Despite the voluminous research on truck platooning, very little has been relevant to provide guidance to departments of transportation for operation in work zones.

This study is the first research project that examined truck platooning in work zones. A networked or federated simulator was used in which a vehicle driven by a human subject encountered a truck platoon with the lead truck driven by a human driver. The experiment involved 10 scenarios composed of differences in education, truck signage, and number of trucks in the platoon.

The results point to the importance of education as the post-education vehicle speeds increased between 8.6% and 12.9% across scenarios, and the distance headways decreased between 28.8% and 30%. The vehicles increased in efficiency while still staying under the work zone speed limit.

On the other hand, the use of truck signage changed driver behavior in an arguably undesirable way by increasing the percentage of platoon bypasses. As the post-simulator survey revealed, 94% of the subjects believed it was safer not to bypass the truck platoon and yet about 34% chose to do so.

This initial investigation into truck platooning near work zones is a beginning upon which further investigations on education, signage, and platoon size policies can continue.

Project Details
STATUS

Completed

PROJECT NUMBER

20-733

START DATE

01/01/20

END DATE

06/04/21

SPONSORS

Smart Work Zone Deployment Initiative

Researchers
Principal Investigator
Natalia Ruiz-Juri

About the research

This project describes the implementation of machine learning (ML) models to the prediction of work-zone traffic impacts including local speed and traffic volume changes and corridor-level travel time increases. It also summarizes efforts to refine an existing tool that estimates work-zone-related delays and costs by providing consistent estimates of typical travel times that consider variations across days of the week and months of the year.

All of the models described in the report were estimated/trained and tested using data collected on I-35 through Austin, Texas, on a 20.4-mile section on which smart work-zone trailers (SWZTs) were placed. Predictive models combined SWZT point speed and volume data with INRIX segment-level speed data. The researchers implemented artificial neural networks (ANNs) to forecast speed and volume changes for planned closures.

Speed forecasting models performed well on average (root mean square error [RMSE] of 10.19 mph) but tended to underestimate speed reductions when the closures were significant. The latter was likely a result of having a small fraction of time steps exhibiting significant speed reductions in the dataset, which consisted mostly of nighttime closures.

Models used to forecast changes in traffic volumes had an average error (RMSE) of 57 vehicles per hour per lane (vphpl), which was comparable to that of linear regression models. Further training with a more balanced dataset that includes daytime and nighttime closures is required to support a broader set of applications.

The researchers also analyzed the performance of three short-term travel-time prediction (STTTP) methods, trained as part of a separate effort during work zones. The trained models, which included a time series approach and two types of ANNs, were very successful on average, outperforming traditional approaches by up to 50 percent during the peak period. While model performance was not as impressive for predicting travel times when work zones were present, preliminary results were promising with ML models consistently outperforming the traditional approaches.

Further model refinements to explicitly consider the presence of work zones and their characteristics are expected to improve model predictions. The efforts described in this project illustrate the potential value of emerging data sources and modeling techniques to support work-zone planning and management.

Project Details
STATUS

Completed

PROJECT NUMBER

21-756, TPF-5(438)

START DATE

03/01/21

END DATE

09/30/23

FOCUS AREAS

Safety

RESEARCH CENTERS InTrans, CTRE, SWZDI
SPONSORS

Iowa Department of Transportation
Smart Work Zone Deployment Initiative

Researchers
Principal Investigator
Jing Dong-O'Brien

Transportation Engineer, CTRE

Co-Principal Investigator
John Shaw
Co-Principal Investigator
Skylar Knickerbocker

Research Scientist, CTRE

About the research

Rear-end collisions in work zones, induced primarily by speeding and tailgating, are a predominant concern for roadway safety. Although considerable research has shed light on the dangers and implications of speeding within these zones, there exists a conspicuous research gap on tailgating behaviors.

To address this gap, the present project was conducted in two main phases. In the first phase, a message design and comprehension test involved the development of graphics and messages tailored for both fixed signs and dynamic message signs (DMS). These messages were constructed to ensure not only that drivers understood them with ease but also that the messages emotionally resonated with drivers and conveyed positive sentiments. In the subsequent field test phase, the designed signs were installed in work zones to evaluate their effectiveness in real-world settings. Two key performance metrics, namely, the average vehicle headway and the probability of tailgating occurrences, were used for this evaluation.

Preliminary surveys among potential users indicated a strong inclination towards messages with a positive tone and without numerical specifics, underscoring the importance of the messages’ lucidity and favorable reception. Field evaluations carried out at single-lane closure and shoulder closure construction sites demonstrated the efficacy of the signs evaluated in the surveys. There was an increase in average vehicle headway and a reduction in the probability of tailgating occurrences at both sites. Collectively, this research provides meaningful insights into tailgating behaviors in work zones, bridging the knowledge gap and laying a foundation for work zone safety strategies.

Project Details
STATUS

Completed

PROJECT NUMBER

TPF-5(295), 18-646

START DATE

01/01/18

END DATE

03/23/21

FOCUS AREAS

Safety

RESEARCH CENTERS InTrans, CTRE, SWZDI
SPONSORS

Iowa Department of Transportation
Smart Work Zone Deployment Initiative

Researchers
Principal Investigator
Anuj Sharma

Co-Director, REACTOR

Co-Principal Investigator
John Shaw

About the research

Highway work zones often have major safety and mobility impacts, which are made worse when travelers are unaware that they are approaching a work zone. To monitor and mitigate the mobility and safety impacts of road construction, transportation agencies, first responders, and the public require accurate information about the location, extent, and timing of construction-related closures.

This project reviewed various stakeholders’ current needs for pre-construction, real-time, and post-construction work zone information and compared these needs to the available work zone data sources and standards. The analysis identified a substantial mismatch between the roadway and lane closure data currently available and the data required to manage work zone traffic impacts effectively. To address this gap, the project developed a conceptual prototype for a tool that would facilitate self-reporting of closure details by contractors and maintenance crews.

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