Disclaimer
The contents of this report reflect the views of the authors, who are responsible for the facts and
the accuracy of the information presented herein. This document is disseminated in the interest
of information exchange. The report is funded, partially or entirely, by a grant from the U.S.
Department of Transportation’s University Transportation Centers Program. However, the U.S.
Government assumes no liability for the contents or use thereof.
TECHNICAL REPORT DOCUMENTATION PAGE
1. Report No.
04-104
2. Government Accession No.
3. Recipient’s Catalog No.
4. Title and Subtitle
Development of a Connected Smart Vest for Improved
Roadside Work Zone Safety
5. Report
DateApril
2021
6. Performing Organization Code:
7. Author(s)
Nazila Roofigari-Esfahan (VT)*
Elizabeth White (VTTI/VT)
Mike Mollenhauer (VTTI/VT)
Jean Paul Talledo Vilela (VTTI/VT)
8. Performing Organization Report
No.Safe-D 04-104
9. Performing Organization Name and Address:
Safe-D National UTC
[Virginia Tech
Virginia Tech Transportation Institute]
10. Work Unit No.
11. Contract or Grant
No.
69A3551747115/04-
104
12. Sponsoring Agency Name and Address Office
of the Secretary of Transportation (OST)
U.S. Department of Transportation (US DOT)
13. Type of Report and
PeriodFinal Research Report
14. Sponsoring Agency Code
15. Supplementary Notes
This project was funded by the Safety through Disruption (Safe-D) National University Transportation Center, a
grant from the U.S. Department of Transportation – Office of the Assistant Secretary for Research and Technology,
University Transportation Centers Program.
16. Abstract
Roadside work zones (WZs) present imminent safety threats for roadway workers as well as passing motorists. In
2016, 764 fatalities occurred in WZs in the United States due to motor vehicle traffic crashes. A number of factors
(aging highway infrastructure, increased road work, increased levels of traffic and more nighttime WZs) have led
to an increase in WZ crashes in the past few years. The standard WZ safety signage and personal protective
equipment worn by workers at roadside WZs have not been completely effective in controlling WZ crashes. This
project aims to address this issue by designing a wearable device to accurately localize, monitor, and predict
potential collisions between WZ actors based on their movements and activities, and communicate potential
collisions to workers, passing drivers, and connected and automated vehicles (CAVs). Through this project, a
wearable worker localization and communication device (i.e., Smart Vest) was developed that utilizes the
previously developed Threat Detection Algorithm to communicate workers’ locations to passing CAVs and
proactively warn workers and passing motorists of potential collisions. As a result, this research is expected to
significantly improve the safety conditions of roadside WZs through prompt detection and communication of
hazardous situations to workers and drivers.
17. Key Words
Smart Vest; Work zone Safety; Worker Safety;
Connected Vehicles;
18. Distribution Statement
No restrictions. This document is available to the
public through the Safe-D National UTC website,
as
well as the following repositories: VTechWorks, The
National Transportation Library, The Transportation
Library, Volpe National Transportation Systems
Center, Federal Highway Administration Research
Library, and the National Technical Reports Library.
19. Security Classif. (of this report)
Unclassified
20. Security Classif. (of this
page) Unclassified
21. No. of Pages
20
22. Price
$0
Form DOT F 1700.7 (8-72) Reproduction of completed page authorized
ii
Abstract
Roadside work zones (WZs) present imminent safety threats for roadway workers as well as passing
motorists. In 2016, 764 fatalities occurred in WZs in the United States due to motor vehicle traffic crashes.
A number of factors (aging highway infrastructure, increased road work, increased levels of traffic and
more nighttime WZs) have led to an increase in WZ crashes in the past few years. The standard WZ safety
signage and personal protective equipment worn by workers at roadside WZs have not been completely
effective in controlling WZ crashes. This project aims to address this issue by designing a wearable device
to accurately localize, monitor, and predict potential collisions between WZ actors based on their
movements and activities, and communicate potential collisions to workers, passing drivers, and connected
and automated vehicles (CAVs). Through this project, a wearable worker localization and communication
device (i.e., Smart Vest) was developed that utilizes the previously developed Threat Detection Algorithm
to communicate workers’ locations to passing CAVs and proactively warn workers and passing motorists
of potential collisions. As a result, this research is expected to significantly improve the safety conditions
of roadside WZs through prompt detection and communication of hazardous situations to workers and
drivers.
Acknowledgements
This project was funded by the Safety through Disruption (Safe-D) National University
Transportation Center, a grant from the U.S. Department of Transportation – Office of the
Assistant Secretary for Research and Technology, University Transportation Centers Program.
The research team would like to acknowledge the support from the Virginia Department of
Transportation and the Myers-Lawson School of Constructions’ Industry members, who assisted
with user surveys and field experiments. We also appreciate the support and feedback provided
by the project’s subject matter expert, Dr. Reza Akhavian.
iii
Table of Contents
INTRODUCTION............................................................................................................................. 1
Research Question(s) ................................................................................................................................................... 2
METHOD ......................................................................................................................................... 2
Task 1: Project Management ...................................................................................................................................... 2
Task 2: Design Requirements ..................................................................................................................................... 2
Task 3: Hardware Component Specification ............................................................................................................ 3
Task 4: Platform Development ................................................................................................................................... 6
Smart Vest RTK System ........................................................................................................................................... 6
GPS RTK Verification .............................................................................................................................................. 8
Task 5: Build the Smart Vest ...................................................................................................................................... 9
RESULTS ....................................................................................................................................... 11
Smart Road Tests .................................................................................................................................................... 11
Work Zone Polygon Validation .............................................................................................................................. 11
Smart Vest Assessment ............................................................................................................................................. 12
Demonstration ............................................................................................................................................................ 14
Field Experiment..................................................................................................................................................... 15
DISCUSSION ................................................................................................................................. 17
ADDITIONAL PRODUCTS ............................................................................................................ 17
Education and Workforce Development Products ................................................................................................. 17
Technology Transfer Products ................................................................................................................................. 18
D
ata Products ............................................................................................................................................................. 19
REFERENCES ................................................................................................................................. 20
iv
List of Figures
Figure 1. U-Blox receiver ............................................................................................................................. 4
Figure 2. Zigbee communications module .................................................................................................... 4
Figure 3. Gateway microprocessor (Raspberry Pi 4 ) ................................................................................... 4
Figure 4. LED strips ...................................................................................................................................... 5
Figure 5. Haptic tactors ................................................................................................................................. 5
Figure 6. Audio buzzer .................................................................................................................................. 6
Figure 7. Harness used to mount sensors ...................................................................................................... 6
Figure 8. Smart Vest RTK System. ............................................................................................................... 7
Figure 9. Final system configuration. ........................................................................................................... 8
Figure 10. GPS RTK correction. ................................................................................................................... 8
Figure 11. Physical hardware of the Smart Vest ......................................................................................... 10
Figure 12. Validation of safety zones.......................................................................................................... 11
Figure 13. GPS system hardware components ............................................................................................ 12
Figure 14. Smart Vest assessment setup ..................................................................................................... 13
Figure 15. Safety zone validation. ............................................................................................................... 13
Figure 16. Communication range validation.
.............................................................................................. 14
Figure 17. VTTI’s Smart Vest demo at the Virginia Smart Roads. ............................................................ 15
Figure 18. Realization of the worksite and collected location data for field study. .................................... 16
Figure 19. WZ setting for the field experiment ........................................................................................... 16
List of Tables
Table 1. Participant Experience .................................................................................................................... 3
Table 2. The Top Two Alarm Methods in Different Environmental Situations and Activities .................... 3
Table 3. Developed Safety Zones ............................................................................................................... 11
1
Introduction
Roadside work zones (WZs) present imminent safety hazards for roadway workers as well as passing
motorists. In 2016, 764 fatalities occurred in WZs in the United States due to motor vehicle traffic crashes
(National Work Zone Safety Information Clearinghouse, 2017). In 2017, a WZ crash occurred once every
5.4 minutes in the U.S., adding up to an estimated 96,626 crashes in WZs, a 7.8% increase over 2014 and
a 42% increase over 2013 (Work Zone Management Program, n.d.). The increase in WZ crashes can be
attributed to a number of factors. The nation’s highway infrastructure is aging, causing the need for
rebuilding and improving existing roadways. This increased road work is being completed on roadways
experiencing increased levels of traffic, especially in urban areas, often resulting in nighttime WZs to avoid
peak travel times (Work Zone Management Program, n.d.). These factors result in more dangerous
situations for workers and for passing vehicles. Accordingly, accidents involving motor vehicle collisions
are a leading cause of roadside WZ fatalities. An average of 121 workers per year lost their lives at roadway
WZs between 2003 and 2015 (Highway Work Zone Safety, 2017; Fyhrie et al., 2016). Transportation events
accounted for 73% of these fatalities, 61% of which were due to a worker being struck by a vehicle in the
WZ (Highway Work Zone Safety, 2017; Guo et al., 2017).
Between 2005 and 2010, vehicle collisions were the second most common cause of worker fatalities in
roadside WZs, after runovers/backovers by construction equipment (Work Zone Management Program,
n.d.). WZs and the presence of workers within them often violate driver expectations and as a result,
workers and passing traffic are placed in unsafe proximity to each other. Successful WZ safety management
hinges on detailed and early detection of threats, especially closeness of the workers to passing traffic, and
sending timely information to workers and passing drivers. Furthermore, advanced warning of worker
presence can help both human drivers and connected/automated vehicles (CAVs) prepare for and avoid
collisions with WZ actors.
Standard WZ safety signage and personal protective equipment worn by workers at highway work sites
have not been completely effective in controlling WZ crashes. Previous research conducted by team
members has focused on improving roadway workers’ safety through both worker trajectory planning
(Roofigari-Esfahan et al., 2015; Roofigari-Esfahan et al., 2017) and the design of a wearable GPS-based
communication system (Bowman & Martin, 2015). Additionally, in a previous Safe-D project (03-050),
the project team developed and validated a Threat Detection Algorithm to detect potentially unsafe
proximities between workers on foot, equipment, and CAVs. As such, the overarching goal of this research
is to design and develop a smart wearable device that increases roadway workers’ situational awareness
and to inform workers and CAVs about detected hazardous situations to avoid imminent safety hazards. To
this end, the team designed and built a prototype for a Smart Vest—a deployable roadside WZ wearable
localization and warning system—to increase situational awareness of workers and CAVs by providing
collision-imminent warnings. The Smart Vest utilizes current and emerging transformative technologies in
conjunction with CAVs to minimize the increasing safety risks associated with roadside WZs. Equipping
roadway workers with the technology to ultimately communicate with approaching CAVs can help
eliminate imminent safety hazards associated with passing CAVs before they occur and reduce the
occurrence of accidents by alerting workers about unsafe exposures.
2
Research Questions
The research addresses the following research questions:
1. What are the design requirements for the Smart Vest, including localization, communication and
human-machine interface (HMI) technologies?
2. What are the best hardware components currently available to satisfy the identified design
requirements and how will those components work together to achieve the desired functionality
from the Smart Vest?
3. What backend platform configuration will enable the desired functionalities? What strategies
should be utilized for sensing, actuation, and communication?
4. What is the best physical layout for the Smart Vest that is convenient and comfortable for
workers while minimizing distraction?
Method
The team completed the following tasks for developing the specification and prototype for the Smart
Vest:
Task 1: Project Management
Throughout the life of this project, the project team held biweekly teleconferences to discuss project status.
Status meetings included discussion of the milestones/deliverables’ schedule to include quarterly reports,
biannual activity surveys, and the final project report.
Task 2: Design Requirements
During this research task, the design requirements for the technologies used in the Smart Vest were
investigated. For this purpose, the team completed an extensive review of current WZ safety practices and
standards governing High Visibility Safety Apparel (HVSA) in terms of material, configuration and other
requirements under various work conditions. The ANSI 2010 standard requirements for HVSA Type R
(roadway) class II was reviewed to comply with Virginia Department of Transportation (VDOT) practices.
The requirements included background and retroreflective materials as well as configuration and
ergonomics of the apparel. The project was presented to construction industry professionals, including
contractors and project managers, to collect feedback from field practitioners regarding practical
requirements of a wearable device that can replace conventional HVSA and can be used without adding a
burden to workers. Based on the discussions, the team concluded the most practical configuration for the
vest was to design the technology components into detachable elements to augment the conventional vests
(e.g., into detachable reflective bands around the waist).
The team conducted a comprehensive review of the literature and industry practices about sensing and
human factors relating to a wearable vest and feasibility of the related technologies for use in roadway WZs.
The investigated technologies included location sensing devices, HMI modes, and related sensors and
communication technologies. The review focused on technical requirements for viable technologies that
can be conveniently used in roadway WZ conditions and that can convey the required results. The location
sensing requirements were studied in terms of requirements for accuracy, latency, durability, weight, and
3
feasibility for use in roadway WZ environments. The viable HMI modes were found to be haptic, auditory
and visual (lighting).
In order to collect user feedback regarding the comfort and practicality of each HMI mode and
configuration, the team designed a user survey focusing on understanding worker preferences, priorities,
convenient HMI modes, and optimal locations of the related technologies on a wearable vest. The survey
was designed in online format and was sent to roadway construction practitioners, including private
companies such as Keiwit, Forrestconstruction, WMJordan, etc. The survey was completed by 25 highway
construction workers. Of those responding, 72.00% had more than 10 years’ experience in the industry
(Table 1). The occupations included project managers, safety specialists, flaggers, and paving workers.
Table 1. Participant Experience
Years of Experience
% of Total Participants
Count
0–3
0.00%
0
3–10
28.00%
7
> 10
72.00%
18
Total
100%
25
Noise (56.25% strongly agree), darkness (75% strongly agree), and weather (42.55%) were found to be the
environmental elements that most negatively impact workers’ ability to detect a hazard. To understand
workers’ alarm method preferences under different environmental situations as well as their working
activities, a Likert scale with weighted numerical values were assigned a ranking from 1–7, with 7 being
the most preferred. The top two alarm methods under each situation are presented in Table 2. Among all
the alarm methods, the combination of Auditory + Haptic + Visual was the most preferred under all the
circumstances. Auditory + Visual received the second highest score in almost all situations. Participants’
responses further emphasized the importance of considering workers’ activities in predicting unsafe
proximities and selection of HMI method. For instance, although workers considered a haptic alarm to be
the most robust method, the comfort of auditory and visual alarms were dependent upon the type of
activities. For example, visual alarms were deemed more preferable for activities such as jackhammering
work, where high levels of activity noise impair hearing. In addition, using combination warnings can help
workers with visual or hearing disabilities better receive alarms and prevent imminent threats.
Table 2. The Top Two Alarm Methods in Different Environmental Situations and Activities
Rank 1 Alarm
Total Score
Rank 2 Alarm
Total Score
Day
Auditory + Haptic +Visual
226
Auditory + Visual
Auditory + Haptic
206
Night
Auditory + Haptic +Visual
231
Auditory + Visual
212
Walking
Auditory + Haptic + Visual
242
Auditory + Visual
202
Jackhammering
Auditory + Haptic + Visual
219
Visual
203
Rolling
Auditory + Haptic + Visual
217
Auditory + Visual
198
Guiding
Auditory + Haptic +Visual
232
Auditory + Visual
194
Random
Auditory + Haptic + Visual
227
Auditory + Visual
198
Task 3: Hardware Component Specification
The research team conducted a comprehensive review of the literature and off-the-shelf technologies to
select alarm hardware components, focusing on identifying components that were small and lightweight,
while satisfying the design requirements. A U-blox multi-band GNSS receiver (Figure 1), which provides
4
real-time kinematic (RTK) GPS data, was selected for localization. This component is small and
lightweight, has an advertised accuracy of 0.01 m, and utilizes the following GNSS: BeiDou, Galileo,
GLONASS, and GPS/QZSS.
Figure 1. U-Blox receiver.
The communications component selected by the project team was a Digi XBee 3 Zigbee 3 module (Figure
2). This component supports communications between each Smart Vest unit (or node) and the gateway,
broadcasting the RTK GPS data and sending HMI requests to trigger the associated Smart Vest sensors
based on the collision detection algorithm. This unit is compact (13 mm x 19 mm). The gateway or sentinel
device is the central unit that facilitates communication between the Virginia Connected Corridor (VCC)
Could Server and the Smart Vest nodes.
Figure 2. Zigbee communications module.
A Raspberry Pi 4 was selected as the microprocessor acting as the “brain” of the gateway (Figure 3).
Figure 3. Gateway microprocessor (Raspberry Pi 4 ).
The gateway runs a threat detection algorithm developed by the research team that utilizes polygons
representing roadside WZ boundaries, and detects when the Smart Vest nodes needs to be alerted of
potential threats. The polygons can be created using two methods. First, a physical device can be used at
5
WZs to plot out the points of a polygon that make up a WZ’s activity area. This device is considered another
node, similar to the Smart Vest nodes, but does not contain an HMI component. Second, the system will be
integrated with the VCC Cloud and can utilize the Work Zone Builder application (a mobile application
that members of the research team created to digitize roadside WZ boundaries and other components) and
the digital boundaries identified for each WZ created by the application.
The HMI sensors integrated into the Smart Vests include LEDs, haptic tactors, and audio speakers that
provide patterned warnings to alert roadside workers of various conditions while working. These sensors
are controlled by a processor embedded into the Smart Vest board.
The LED strips chosen by the team (two per vest) are flexible. The white LED light strips are shown in
Figure 4 below.
Figure 4. LED strips
The haptic tactors (four per vest) are small (8.7 mm) and provide a vibration speed of 13,800 rpm and 7 G
amplitude (see Figure 5).
Figure 5. Haptic tactors.
The buzzers/speakers (two per vest) provide 100 dB at 5 V as shown in Figure 6 below.
6
Figure 6. Audio buzzer.
Based on the user feedback collected through the survey and discussion with industry practitioners, the
team concluded that sensors should be built as easily detachable components from the vest garment, so that
the garment can be laundered as needed. Therefore, the equipment was integrated into a harness (Figure 7)
which will be worn underneath the conventional vest. The designed harness can be attached to a Class 3
roadside worker vest that can be purchased separately.
Figure 7. Harness used to mount sensors.
Task 4: Platform Development
The gateway hosts the developed software and algorithms that constantly localize workers, detect potential
threats, and warn workers about those threats. To this end, the gateway is integrated with a GPS plotter
device. This allows the GPS points that correspond with a roadside WZ to be instantiated into the system
and used to determine potential threats to the Smart Vest wearers and passing CAVs. The gateway can also
receive information regarding WZ boundaries from the Work Zone Builder Smartphone application. The
Builder Smartphone application uses HERE map technology to create a WZ layout which meets VDOT
requirements and generates a GEOJson file which can be downloaded by the Smart Vest base station to
determine potential threats automatically, without needing to use the physical GPS plotter device. The WZ
boundaries are then used to detect extreme proximity to the border (low hazard zone), or when a user is
passing the WZ and stepping into the traffic path (high hazard zone). The system components are detailed
in the following section.
Smart Vest RTK System
The Smart Vest GPS RTK system consists of three main components (Figure 8):
1) Base Station
2) Communication
3) Rover
7
Figure 8. Smart Vest RTK System.
The base station system is the main computing component, transmitting RTK corrections using an XBee
link to the Rovers. It also receives GPS data from the Rovers at 10 Hz and conducts the following
computation tasks:
• Geofencing and Alert triggering for Smart Vest Rover: Each Smart Vest Rover Node can receive
an HMI trigger when there is a WZ polygon in place and the base station detects a change between
a safe zone to a low/high level alert zone. The Smart Vest Rover transmits GPS and inertial
measurement unit (IMU) data to the base station in real-time in order to make the above
calculations. The IMU data (acceleration) is used to determine specific activities performed by the
user and provide specific alerts while those activities are close to a safety-critical geofence.
• Local WZ polygon creation using Geo-Plotter Rover: The Geo-Plotter Rover is used to send precise
GPS position data to the base station for each polygon vertex (WZ boundary coordinates). The
Geo-Plotter has a push button that sends GPS data to the base station for 10 seconds in order to
average and insert it into the polygon creation engine.
Rovers, including the Smart Vest system and the Geo-Plotter for WZ polygon creation, can get within 3 cm
accuracy using the base station’s RTK data. Both systems use a 32-bit microprocessor to receive RTK
corrections and redirect them to the on-board GPS unit to compute and provide a high precision GPS output
back to the microprocessor. The accurate GPS coordinates are then forwarded as GPS packets to the base
station. Communication between the Base Station and Rovers is established using an XBee Link. Providing
up to a 150 m range and multi-node support, the small XBee provides a reliable wireless communications
support mesh, multi-hop, and direct link data transmission. As shown in Figure 9, the final system
configuration shows the Smart Vest device, the Base Station, and the 4G Link to download RTK corrections
from Virginia Tech Transportation Institute’s (VTTI’s) NTRIP Server and to communicate with the VCC
Cloud Server. Both Base Station and Smart Vest devices use the Ublox ZED-F9P RTK-capable GPS
receiver to compute very precise GPS location and transmit that data along with IMU data using the XBee
3.0 RF Link. VTTI designed a stack hardware board which houses the GPS transceiver and the HMI
circuitry for alert triggering. This board goes on top of an NXP development board (FDRM KL28Z), which
uses the NXP KL28Z ARM Microprocessor.
8
GPS RTK Verification
Figure 9. Final system configuration.
The GPS RTK sub-system is based on the Ublox ZED-F9P GPS chip, which provides multiband GNSS
technology and RTK functionality, leading to within 1 cm precision and converge time of less than 10
seconds. Multi-constellation support includes GPS and GLONASS, Galileo, and BeiDou. Using Ublox’s
U-Center software, the Rover can provide high precision GPS data and RTK data reception for GPS solution
computation.
Figure 10 shows Ublox’s GUI, which provides very specific information about the GPS
receiver, satellite information, precision, computation quality, and RTK status. VTTI used this tool to
confirm the GPS accuracy (which averages 2 cm), RTCM/RTK packets (six different packets) and the GPS
computation level (3D/DGNSS/FLOAT) .
Figure 10. GPS RTK correction.
GPS Fix Mode can be explained as follows:
3D: a position solution is achieved with at least four satellites compared to a 2D solution with three
satellites and altitude/vertical metrics locked to a preset value.
9
DGNSS: corrections are provided from a source that measures the differences between what pseudo
range values (the signal’s time-of-flight approximately indicates distance using speed of light
through a medium) for each satellite should be at the precisely surveyed reference station compared
to what is reported by its navigation computation. The differences are generally caused by time-
varying ionospheric perturbations in the path from satellite to the reference station and the nearby
rover. If the rover and reference are too far apart, the separate signal paths may have different
perturbations and the correction data are less effective.
Float and fixed: in precise navigation, the receiver tries to lock onto carrier phase (within the 19
cm wavelength) to resolve the exact wavelengths and fractions to each satellite. If this exactitude
is achieved, the status is "fixed" since phase markers can be locked. If precise wavelengths and
fraction are not achieved, ambiguity persists, and the status is "float" since the carrier phase markers
are not locked but "floating around" in mathematical computation. The difference in fixed position
accuracy is in mm compared to the cm-level float accuracy.
RTCM packets can be classified as follows:
1005
Stationary RTK Reference Station ARP
Commonly called the Station Description, this message includes the Earth-Centered, Earth-Fixed
location of the antenna (the antenna reference point [ARP] not the phase center) and the quarter
phase alignment details. The datum field is not used/defined, which often leads to confusion if a
local datum is used. See message types 1006 and 1032. The 1006 message also adds a height
about the ARP value.
1074
GPS MSM4
The type 4 Multiple Signal Message (MSM) format for the U.S.’s GPS system. This is one of the
most common messages found when MSM is being used
1084
GLONASS MSM4
The type 4 MSM format for the Russian GLONASS system.
1094
Galileo MSM4
The type 4 MSM format for Europe’s Galileo system.
1124
BeiDou MSM4
The type 4 MSM format for China’s BeiDou system.
1230
GLONASS L1 and L2 Code-Phase Biases
This message provides corrections for the inter-frequency bias caused by the different frequency-
division multiple access frequencies (FDMA; k, from -7 to 6) used.
Task 5: Build the Smart Vest
The team built upon the two prior versions of the Smart Vest (Alpha and Alpha Plus) to create the final
Beta version. Final hardware selections have been made as described in the Task 3 section of this report.
The team worked with a fashion designer to build three Smart Vests (Beta Version). Working together with
a fashion designer allowed the Vest to be as flat as possible to avoid any issues that might cause discomfort
for the wearer. The harness has snap-on buttons, allowing the Smart Vest to de-attach for
cleaning/maintenance or upgrade purposes. On the belt section, an industrial Velcro strip allows the tractors
to be adjusted in location to provide better sensitivity depending on the wearer’s preferences.
The GPS antenna has a small ground plate on the right shoulder area, which also has a snap-on button. The
ground plate is necessary to acquire more precise satellite data and improve the GPS antenna’s performance.
11
Results
Smart Road Tests
Work Zone Polygon Validation
The base station software can acquire an N-vertex convex polygon and classify/check if a Smart Vest Rover
is in the following zones:
Table 3. Developed Safety Zones
Zone
Definition
High Level threat zone
Any GPS location outside the defined WZ polygon
Low Level threat zone
Any GPS location in between the pseudo-polygon region which is 2
meters under the WZ polygon shape.
Safe Zone
Any GPS location below/inside 2-meter offset from WZ polygon
For this WZ polygon validation, Geo-Plotter was used to create a 4-vertex polygon and acquire GPS data
from one Smart Vest Rover. The base station computer system records a log file with each GPS entry and
the proper classification. The picture below shows the classification: red (high level), blue (low level), green
(safe zone) and 4-vertex polygon (yellow).
Figure 12. Validation of safety zones.
For this field test, the following systems were used (Figure 13):
12
Smart Vest Assessment
Figure 13. GPS system hardware components.
The team conducted testing to evaluate the three developed Smart Vest Beta versions to verify GPS
accuracy, communications range, and battery life. GPS accuracy validation was verified at the VTTI
Automation Hub location, where a rectangle area was marked as a WZ activity area using the GPS Plotter
(four GPS points) as shown in the picture below.
13
Figure 14. Smart Vest assessment setup.
A team member wearing the Smart Vest walked across the blue region while transmitting GPS position
data and a log file was created with area detection and classification. The GPS points were classified as
safe zone (green), low-level warning (blue), and high-level warning (red).
Figure 15. Safety zone validation.
The second test verified the communications range from the Smart Vest Gateway to any node. Using both
versions of the wireless transceiver (XBee) with internal/external antennas, the achieved range was
around 300 m.
14
Figure 16. Communication range validation.
The third test executed was related to battery life. Having a full charged battery, two scenarios were
tested:
1) Smart Vest transmitting only GPS data to Smart Vest Gateway (normal scenario): Battery lasted
20 hours.
2) Smart Vest transmitting GPS and triggering HMI alerts (LEDs, buzzers, and tactors) every 2
seconds: Battery lasted 10 hours.
Demonstration
The team built an additional set consisting of a Smart Vest, GPS Plotter and Base station. These were used
during VTTI’s Smart Vest demo at the Virginia Smart Roads (Figure 17). VCC Connectivity was added to
the Smart Vest software package for this demonstration. The system can connect to VCC and upload basic
safety message packets using Smart Vest GPS locations and can generate virtual worker dots on the VCC
Monitor tool. Future development efforts will allow the Work Zone Builder application support to retrieve
Activity Area information for easy polygon geo-fencing setup.
15
Figure 17. VTTI’s Smart Vest demo at the Virginia Smart Roads.
Field Experiment
The team received Institutional Review Board (IRB) approval and ran a session of field experiments for
testing the three Smart Vest Beta setups to verify GPS accuracy, communications range, and battery life
at a highway construction site at Elliston, VA.
GPS accuracy validation was verified at the worksite, where a rectangle area was marked as a WZ activity
area using the GPS Plotter (four GPS points) as shown in yellow in the picture below.
16
Figure 18. Realization of the worksite and collected location data for field study.
Data was collected from two construction workers wearing the Smart Vest as they conducted earth work
and placed base stones, and a log file was created with area detection and classification. The GPS points
were classified as safe zone (green), low-level warning (blue; within one meter from the border), and
high-level warning (red; at the border). These can also be seen in Figure 18.
The test verified the communications range from the Smart Vest Gateway to any node. Using both
versions of the wireless transceiver (XBee) with internal/external antennas, the achieved range covered
the WZ length of about 500 m. Figure 19 below shows the setting of the experiments and study
participants during different construction activities.
Figure 19. WZ setting for the field experiment.
17
Feedback was also collected from the participants about the comfort and alarms received using the vest.
The collected feedback will be used in the future research to improve the layout of the vest.
Discussion
A number of challenges were encountered during the course of the research. Due to the user-centered nature
of the design, the team decided to conduct a comprehensive formal user survey in addition to the review of
literature and technologies (as discussed in Task 2). The IRB process required for this and collecting the
user preferences delayed the subsequent activities. In addition, during the literature review and user survey,
the importance of accurate activity recognition for predicting unsafe proximities and minimizing false
positive alarms was highlighted. However, the current algorithm does not provide the required accuracy
and requires extensive computational modeling. We believe that this is an essential component that needs
to be addressed for successful implementation of the Smart Vest. As a result, the Smart Vest Rover has an
built-in IMU, which can be used for further activity detection. The research team is working on a subsequent
project (funded by Center for Innovative Technologies) to expand functionalities of the vest and include
the activity recognition in the current algorithm. To this end, a series of field experiments at highway
jobsites will be conducted while using the Smart Vest developed in this research to collect data during
various highway construction activities.
Additional Products
The Education and Workforce Development (EWD) and Technology Transfer (T2) products created as part
of this project can be downloaded from the Safe-D website here.
The final project dataset is located on the
Safe-D Dataverse.
Education and Workforce Development Products
Dr Roofigari-Esfahan developed a graduate course, Advanced Digital Construction and Manufacturing,
that she will teach in Spring 2021. The Smart Vest technologies are presented as technologies that will
change the future of the industry. A demonstration of the vest was given to her undergraduate course (BC
2114-IT in Construction and Design) in Fall 2019 and Fall 2020.
Dr Roofigari-Esfahan presented and discussed the Smart Vest at three committees she is involved in
(construction management, traffic control in WZs and information systems and technology) at the
Transportation Research Board’s (TRB’s) annual meeting in January 2020. She also presented the
technologies at the Construction Research Council (CRC) conference in March 2020.
The vest was also presented to a group of 45 female high school students interested in Construction
Engineering in an event held by the Department of Building Construction at Virginia Tech. The students
had the chance to wear and experience different features of the vest.
Dr. Roofigari-Esfahan has been invited to present her research, including the Smart Vest, as a keynote
speaker at the International Conference and Exhibition on Smart Material and Construction Technology to
be held in Dubai in November 2021.
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Technology Transfer Products
The Smart Vest was presented to industry professionals in different safety events throughout the course of
the research and was very well received. Examples of T2 activities include the following:
Dr. Roofigari-Esfahan presented the initial version of the Smart Vest at Virginia Asphalt Association
(VAA)'s Mid-Atlantic conference and expo on December 11–12, 2019, in Richmond, VA. She
demonstrated the Smart Vest for asphalt workers and collected feedback regarding different features of the
vest. She also presented the Smart Vest and discussed its safety features at the VAA’s Safety committee
meeting.
Dr. Roofigari-Esfahan presented the Smart Vest to the Virginia Tech Honors College’s Industry Board
(consisting of the representatives from Boeing, GE and Caterpillar) on February, 25, 2020. The event was
attended by 20 professionals.
A workshop was held at VTTI on March 11, focusing on another VTTI project that included 12
infrastructure owner/operator (IOO) representatives, including DBi Services, VDOT/VTRC, and
Transurban. During a portion of this workshop, Dr. Mollenhauer presented the overall goals of the Smart
Vest project, the current progress of the Smart Vest project, and demonstrated the Alpha Plus version of
the vest.
Dr. Mollenhauer presented the Smart Vest project goals and status at the ATSSA Annual Convention and
Traffic Expo on January 27, 2021. This presentation was attended by an estimated 45 attendees in New
Orleans.
Dr. Roofigari-Esfahan discussed the Smart Vest features with the TRB Construction management
committee members on June 26 2020. The meeting was attended by 30 professionals.
Dr. Mollenhauer presented the Smart Vest project goals and status at the American Association of State
Highway and Transportation Officials’ Safety Summit meeting on June 17, 2020. This presentation was
attended by an estimated 77 people, including many DOT officials.
Dr. Roofigari-Esfahan discussed the Smart Vest features with the Construction Industry Institute’s (CII’s)
Technology and innovation committee members on September 15, 2020. The meeting was attended by 65
professionals. Interest was shown to demonstrate the Vest at CII’s 2021 conference.
VTTI demonstrated Smart Vest functionality along with other project’s as part of the WZ technologies of
the future. Virginia Tech’s University Relations made a video showing how the Smart Vest can help and
alert works during dangerous situations on the road.
Dr Roofigari-Esfahan is invited to present and discuss the opportunity of further developments of the Smart
Vest at CPWR (the Center for Construction Research and Training) in Maryland. The meeting was
postponed due to the COVID-19 and is expected to be scheduled in summer 2021.
Dr Roofigari-Esfahan is invited to present and discuss the Smart Vest and associated topics in regards to
worker protection innovations at American Traffic Safety Services Association’s virtual Annual
Convention and Traffic Expo in February 2021.
Dr. Mollenhauer presented the Smart Vest in different events including:
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• PA DOT presentation – 10/1/20
• Autonomous Maintenance Technology Pooled Fund – 10/26/20
• 5GAA Virtual Event – 10/27/20
• IOO/OEM RSZW (reduced speed zone warning) subgroup – 11/9/20
• VDOT SORAC meeting – 11/5/20
Data Products
The data uploaded to the Dataverse includes 39,286 datapoints collected on a field test WZ setup at VTTI’s
Automation Hub. The collected data set includes data entries for three Smart Vest devices while moving
around a virtual polygon area defined by the Smart Vest Geo Plotter device. The virtual polygon area was
defined using a four-point polygon (square shape). The three Smart Vests were worn inside and outside the
virtual polygon and their GPS location was processed to calculate their classification and trigger the proper
HMI warnings accordingly when crossing between safe zone, low-level warning areas, and high-level
warning areas. The dataset can be accessed at: DOI:10.15787/VTT1/PMIRWK
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References
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2. Fyhrie, P.B. (2016). Work zone intrusion alarms for highway workers. Caltrans Division of Research,
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