Chapter 2 Methods

This effort was conducted in two phases. During the first phase, the team conducted research to provide an overview of the work zone technology landscape and inform the development of a guidebook for practitioners. In the second phase, the team implemented an Autonomous Truck Mounted Attenuator (ATMA) platform; a Smart Work Zone, including Mover Over Law evaluation; and Zipper Merge applications of work zone technologies selected by the project team and approved by the project panel. The best practices and lessons learned from the proof-of-concept applications further informed the guidebook for practitioners.

Literature Review

A literature review was conducted to evaluate innovative and adaptive technologies that capture attention and enhance work zone safety and mobility. This review encompassed a brief market scan of available technologies and existing scientific research to evaluate their effectiveness. As part of this effort, the practitioner feedback obtained as part of NCHRP 20-102(28) Preparing Transportation Agencies for Connected and Automated Vehicles in Work Zones was leveraged to supplement the literature findings and the team’s understanding of the issues. The spectrum of technologies identified included advanced versions of common devices such as Smart Work Zone ITS, sequential lighting systems, and novel concepts such as wearable alert vests for work zone workers, connected vehicle technologies, and crowdsourced information that can be tracked through mobile applications. Evaluations into the use of crowdsourcing applications and data analytics for dynamic work zone devices and in-vehicle notifications for traffic management were also summarized. Further, the team also reviewed emerging work zone safety technologies and pilot projects where technology demonstrations are in progress. Based on the review of existing literature, important gaps were identified that could be addressed with modern technologies:

1. The strategies detailed in the dissemination of traveler information include using mass media, websites, emails, printed materials, and dynamic message signs (DMS). These strategies have not kept pace with technological advancements, especially in the age of CAVs, and would greatly benefit from a modern update to include modern social media platforms, mobile navigation applications, and crowdsourcing technologies.
2. Most emerging technologies are being developed and tested in isolation. To accurately understand their performance and their drawbacks, these technologies need to be evaluated in realistic environments. Further, economic analyses on these technologies are also needed to determine the cost-benefit to departments of transportation (DOTs).
3. There is a need to develop a catalogue of all the existing and emerging technologies so that practitioners can determine the best combination of technologies that are available and appropriate for the work zone at hand. Such a catalogue needs to be periodically updated with advancements in work zone technologies.

The literature review is included as Appendix A.

Technology Assessment

Next, building upon the foundation provided by the literature review, in-depth evaluations into the emerging technologies were conducted. The project team identified seven major work zone technology use cases that could encompass currently available work zone technologies: traveler

information systems, queue warning systems, work zone intrusion alert systems (WZIAS), systems that detect work zone conditions, speed harmonization systems, speed compliance systems, and dynamic merge assistance systems.

This effort involved a detailed critical assessment of system performance based on data available from past studies. The team also performed an additional meta-analysis to identify trends across systems and deployments and to identify the degree of variability in the impacts, including expected benefits and costs. The data from these meta-analyses were then used to create a taxonomy for evaluating each use case. Within each of these use cases, work zone technologies were evaluated based on their data generation and data dissemination capabilities. Further, each technology was evaluated based on seven factors: maturity, effectiveness, complexity, availability, accessibility, flexibility, and impact (see Table 3). For each of the factors, rubrics were adapted or developed based on existing rubrics, such as FHWA Technology Readiness Levels. In the proposal for this project, the research team also proposed rating costs and benefits of each system. The review revealed that it was extremely difficult to create a consistent taxonomy for costs and benefits due to variations in work zone characteristics, system designs, and level of information available. As a result, costs and benefits are discussed within each use case summary without using a rubric to rate those factors.

Table 3. Preliminary Taxonomy to Compare Methods to Inform Drivers

For the sake of simplicity, a four-level rating (0 to 3) was developed for each of the categories mentioned above. The discussion in each use case was separated based on the methods used for data generation and data dissemination, and multiple options for both functions were reviewed in each use case. Since measures of effectiveness may vary between these functions, Table 4 outlines how the rating rubrics were defined separately for data generation and dissemination. The data generation function and the data dissemination function were expected to potentially vary in rating for some categories; therefore, these categories each have separate columns in the table below to be rated independently. Other categories were expected to address the general nature of the technology and would not vary in ratings between data generation and data dissemination. The rating rubric for evaluating each of the work zone technologies in each of the above-mentioned categories is shown in Table 4.

Table 4. Rating Rubric Used to Evaluate the Work Zone Technologies

Chapter 3 presents a brief summary of the use cases reviewed, a summary table showing the ratings in the taxonomy, and descriptions justifying the taxonomy ratings for each use case. It should be noted that the data generation and data dissemination technologies are sometimes very similar between use cases, so there may be some similarities in the discussions of the same technology in various use cases. In addition, sometimes specific combinations of data generation and data dissemination technologies tend to be deployed in combination. As a result, it may be difficult to fully separate the impacts of the different systems. Cases where this occurred are noted in the summaries.

Stakeholder Workshops

Two virtual workshops were held with stakeholders. During the workshops, stakeholders were presented with an overview of the project’s tasks, a review of the literature findings and the assessments, and a summary of the proposed proof-of-concept technologies. Stakeholder feedback largely focused on capturing appropriate assessments of technologies and on the proof-of-concept activities. This feedback was incorporated into the revised materials presented in this report, as part of the guidebook for practitioners, and into the plans for the proof-of-concept activities.

Development of a Guidebook for Practitioners

Building upon the previous efforts, a guidebook for practitioners was developed. The target audience of the guide will be infrastructure owner operators (IOOs) such as state DOTs and private roadway operators, work zone technology developers, and work zone operations contractors. The products of this work will have broad applicability across most state DOTs.

The organization of the guidebook provides readers with a clear and concise overview of the Smart Work Zone technology use cases, emerging technologies in each of the use cases, and additional resources to support efforts to improve work zone safety and mobility (see Chapter 3); pros and cons of Smart Work Zone technologies (see Chapter 4); and best practices for emerging technologies in Smart Work Zones (see Chapter 5). The document first outlines the learning outcomes for users to achieve after reading the guide. The guidebook describes the major use cases that encompass currently available work zone technologies. The guidebook also rates Smart Work Zone technologies on a four-point scale ranging from 0 to 3 to determine their readiness for scaled-up deployment. Emerging technologies in each of the seven major Smart Work Zone technology use cases are listed. The pros and cons of each technology are briefly described to help readers understand the benefits and drawbacks of each technology, and then best practices for each topic are briefly described to provide practical guidance on adopting emerging technologies in Smart Work Zones. The last section lists additional resources related to Smart Work Zone technologies, including reports, guides, and websites that offer further information.

Proof-of-Concept Activities

While work zones can be similar in nature, very few are exactly alike. Attributes like road geometry, anticipated daily traffic, lateral and longitudinal dimensions of the zone itself, volume of personnel and equipment in the zone etc., prevent all zones from having the same planning and approach. Therefore, each zone requires a fresh perspective and implementation of technologies and processes appropriate for the tasks being performed.

Automated Truck-Mounted Attenuator

The first opportunity to test proposed solutions involved a mobile work zone performing pavement marking painting operations. The team initiated this work by contacting the local DOT District Traffic Operations Center and identifying the key personnel responsible for work zone scheduling and logistics. After providing our stated goals and high-level context on the potential value of the solutions, we tentatively scheduled two sessions for testing. The sessions were dependent on roadway temperature in the region being greater than 50 degrees and weather that did not involve any kind of visible moisture on the roadway.

The technology being tested was an autonomous truck-mounted attenuator (ATMA), developed with the goal of removing vulnerable personnel from high-risk areas of a mobile work zone. Designed to operate in a leader-follower scenario, a leading vehicle in the work platoon contained a technology package that created a set of digital “breadcrumbs” that provided a path for a driverless ATMA positioned at the rear of the zone. The ATMA was controlled remotely via tablet by an operator in a safe position within the platoon, following at a range that could be varied between 25 to 400 feet, and with lateral offsets as much as 12 feet of center in either direction.

Testing began with a safety briefing for DOT personnel. This included an overview and walkthrough of the ATMA system by Virginia Tech Transportation Institute (VTTI) staff, detail

on major components and emergency procedures, and communications between VTTI and DOT personnel while in motion.

Work crew personnel rotated into the ATMA and rode with a safety driver to observe the system in operation, then provided feedback on system deficiencies and suggested improvements. Multiple DOT engineers provided personal insight and proposed improvements to the system interface, noted scenarios that merited consideration, and gave opinions on the sensitivity of the equipment. Questions ranged from security of communications, emergency procedures for system shutdown, and controlling the unit during platoon maneuvers such as U-turns and passing through traffic light-controlled intersections where the light may turn red.

Smart Work Zone Technologies/Dynamic Zipper Merge Evaluation

Subsequent work consisted of field tests with Smart Work Zone technologies and a commercially available Dynamic Zipper Merge System (DZMS). Similar planning and coordination efforts were initiated with DOT leadership to identify projects that met the requisite criteria. Ideally, the projects would consist of at least one static lane closure on a multi-lane roadway, with approximately 2 miles of free-flow travel approaching a tapered merge, and multiple personnel operating in the active zone.

To properly evaluate the effectiveness of the DZMS, minimum data output requirements were defined. Essential metrics included average speed per lane (from radar) and headway variance; additional metrics included traffic volume information, queueing information, vehicle speed information, merging behavior, crash data, vehicle classification, and public awareness.

System components were identified. These differed by work zone, road geometry, and quantity of lanes. In this situation, a minimum of three portable changeable message signs (PCMS) with integrated traffic-sensing devices and three standalone devices were desired. Three devices were of the doppler type, and three devices were higher-capability side-fire radar, which would return more precise traffic flow data.

For these deployments, the Smart Work Zone technologies included a solar trailer with multiple cameras and speed sensors, placed at the merge point near the entrance to the zone. Data storage and supporting infrastructure were housed on the trailer in a waterproof, lockable enclosure. The solar trailer consisted of two 400-W panels linked to four 12-V 200-Ah batteries. The depletion rate from the technologies deployed was expected to result in approximately 118 hours of consecutive data collection without need of recharging. Based on expected and historical seasonal weather patterns in the area, this was deemed sufficient to support collection efforts. The cameras on the trailer were chosen specifically to validate the DZMS data output and vehicle classifications and could be adjusted (pan/tilt/zoom) for 360-degree viewing of the work zone area. The technologies were co-located on an elevated mast and used simultaneously during data collection efforts.

The Smart Work Zone trailer also served as a base station to support interaction with smart alerting devices (helmets/vests) worn by work zone personnel. The trailer system tracks worker positioning and presence using wireless communication and real-time kinematic (RTK) GPS. Using cellular vehicle-to-everything (C-V2X) technology, their position is broadcast into personnel safety messages, so CAVs equipped with C-V2X technology could potentially receive notifications of worker presence. It creates a mesh network of up to 1,000 feet in length and can be extended with the use of additional base stations with flexible mounting options.

The trailer and DZMS systems were deployed together 1 week prior to the estimated start of zone work. This “burn in” period allowed for configuration, optimization, and performance testing without any display of messages to roadway vehicles. Additionally, it allowed for calibration of radar and camera sensors and settings to account for night operations and assess communications (5G/Latency/Video Streaming). The 1-week period also ensured that the placement of the additional monitoring equipment would not negatively impact the expected performance of the DZMS technology. Many trailers of this size and capability are restricted to lower travel speeds—additional time was allowed for transport and staging. Like the DZMS system components, solar trailer collection systems were implemented with remote monitoring capabilities. An on-site team member monitored basic system performance and assessed any daily damage to components, while subject matter experts in each technology area confirmed data integrity and performance of components.

The remoteness of the work zone area caused some concern regarding communications, specifically communication between DZMS system components and their supporting infrastructure, and communication between support personnel and the data collection equipment. As mentioned above, the burn in period allowed for communication validation, which was essential to gauge the available bandwidth in potentially sub-optimal conditions. Near real-time video, used to monitor the work zone, was achieved by using compressed video streamed to VTTI’s WebRTC, while storage space and CPU requirements were reduced by compressing the stored JPEG images.