A recently completed NJDOT research study, Innovative Pothole Repair Materials and Techniques, tested several new techniques and materials that could improve the cost-effectiveness of pothole repairs in New Jersey. Phase I of the research project, led by Professors Hao Wang and Husam Najm of Rutgers University, evaluated new methods for both asphalt and concrete structures. Pothole repair is one of the primary maintenance activities for highway agencies, generating significant costs and resource commitments. Cost-effective pothole repair methods can reduce or eliminate the possibility of re-patching and save future repair costs.
Asphalt Pothole Repair
Asphalt pavement is continuously subjected to vehicular and environmental loading throughout its lifecycle, leading to the inevitable occurrence of distresses such as cracking, rutting, raveling, potholes and so on. Among these distresses, potholes are critical as they can disrupt traffic, impose risks to safety, and cause costly vehicular damage for vehicle operators.
Field repair of pothole using induction heating.
Pothole repair is a primary maintenance activity for highway agencies. Typically, cold mix asphalt is used for emergency repair and hot-mix asphalt (HMA) for traditional repairs. Usual pothole repair methods include throw and go (roll), edge seal, semi-permanent, spray injection, and full depth repair. Among them, throw and go (roll) method using HMA has been adopted by most transportation agencies for surface patching. However, this common practice largely relies on the usage of HMA. Although the quality of the asphalt patch can be ensured, it presents environmental concerns due to the energy consumption and environmental footprint involved in producing new HMA. To mitigate the impact on the environment, reduce cost and conserve energy, recycled asphalt pavement (RAP) has been widely used as a highly desirable material. The addition of recycled asphalt pavement (RAP) in asphalt mixtures can bring numerous economic and environmental advantages.
Infrared heating test was used in asphalt repair method.
This study sought to investigate an innovative approach to pothole repair using HMA with RAP and preheating. The study investigated two aspects: First, the performance of HMA with different RAP contents were evaluated through laboratory tests to select the most appropriate content. Second, the in-site strength of pothole repair was evaluated with field cores to quantify the benefits of repair quality due to recycled material and preheating.
Both microwave heating and infrared heating were tested, with varying results. Microwave heating was able to warm both the surface and internal materials of the pavement, however, its efficiency was low and the rate of temperature increase was insufficient. Conversely, the infrared heating method proved adept at rapidly heating the top edges and bottom surface of the pothole to high temperatures and was used successfully in pothole repair.
Further tests were carried out adding RAP to HMA patching materials. The results showed that there was greater abrasion loss, reduced IDT (indirect tensile strength), and interface shear strength of patching material had less resistance to moisture as RAP content increased. Nonetheless, with the application of preheating, the overall performance of HMA containing 30 percent RAP was satisfactory, proving that it is feasible to use RAP material for pothole repair.
Concrete Pothole Repair
Photos showing condition ratings for concrete repairs.
Similar to asphalt pavement, concrete structures are prone to deterioration due to vehicles and weathering. Cracks can develop which lead to further deterioration due to chloride infiltration. Thus, a good repair is necessary for maintaining concrete structures. An ideal repair material should be easy to work with under different weather conditions, be fast setting, and possess good durability. Rapid-setting cementitious patch repair materials are popular for repairing small concrete damage and providing a functional repair within few hours.
Based on extensive literature research and several NJDOT practices, three formulations were chosen as the best performing candidates. Workability, strength, and restrained shrinkage cracking of the formulations were investigated. The restraint shrinkage test protocol simulated upper and lower limits of restraint that a repair material undergoes in real applications. The repairs were also cast and placed in external environmental conditions to expose them to natural weathering actions. The cracking behavior was evaluated including cracking spacing and maximum crack width
The investigation led to the identification of three formulations that did not crack for a period of 10 months in field exposure to NJ climate conditions. Typically, rapid set formulations do not shrink after 6 months. The formulations that did crack revealed that an addition of 1 percent of PVA fibers could significantly reduce the maximum crack width. The maximum crack widths observed in all the formulations were an order of magnitude less than the maximum allowable crack width specified by NJDOT (1/32″).
Contemplated Legislation
The research projects were completed at a time when pothole repairs have attracted critical attention from motorists and legislators within the state. In the current legislative session (2024-2025), the New Jersey State Senate voted unanimously to advance a bill that is intended to address concerns about pothole damage to roads and bridges in the Garden State.
The NJ Senate bill, S862, would require the state DOT to include information about pothole repair projects and their cost in the annual report. The additional information would include reporting on the number of repair projects going on around the state and their cost. The bill includes a separate provision that would require a lifecycle cost analysis to be conducted. The information would be required to be made available to the public on the NJDOT’s website. An identical bill, A2596, was introduced in the NJ Assembly during the legislative session.
AASHTO Recognition
The research project is not only primed to inform the serious legislative issues being raised in Trenton but was recently recognized by the American Association of State Highway Officials (AASHTO) for its contribution to innovation. Every year, the High Value Research Task Force of AASHTO Research Advisory Committee (RAC) holds a national competition to find “high value” research projects throughout the country. In 2024, the Innovative Pothole Repair Materials and Techniques research project was recognized in the Maintenance, Management, and Prevention supplemental category, as described here.
RESOURCES
Wang, Hao, and Xiao Chen. “Innovative Pothole Repair Materials and Techniques Volume I: Asphalt Pavement.” (2024). Final Report. Retrieved here.
Wang, Hao, and Xiao Chen. Innovative Pothole Repair Materials and Techniques Volume I: Asphalt Pavement. (2024). Technical Brief. Retrieved here.
Najm, Husam, Bala Balaguru, Hao Wang, Hardik Yagnik, and Alissa Persad. “Innovative Pothole Repair Materials and Techniques Volume II: Concrete Structures.” (2024). Final Report. Retrieved here.
Asphalt Pavement Pothole Repair with Recycled Material and Preheating. Presentation at NJDOT Research Showcase by Xiao Chen and Hao Wang. Retrieved here (Presentation) and here (Recording).
The Bureau of Research, Innovation and Information Transfer (BRIIT) is active in many national transportation efforts, including the American Association of State Highway Transportation Officials (AASHTO). Dr. Giri Venkiteela, Research Scientist, BRIIT, is the Vice Chair of Region 1 of AASHTO’s Research Advisory Committee (RAC) that serves the Special Committee on Research & Innovation (R&I).
In late July 2024, he attended the RAC’s National Meeting in Columbus, Ohio and accepted two awards on behalf of the New Jersey Department of Transportation.
Every year, the High Value Research Task Force of AASHTO RAC holds a national competition to find four “high value” research projects from each of the four AASHTO regions in the country. In 2024, two research projects sponsored and managed by the New Jersey Department of Transportation were recognized nationally with awards.
Several experimental and numerical research activities were carried out to assess the mechanical properties and long-term durability of Advanced Reinforced Concrete materials
The first project, Advanced Reinforced Concrete Materials for Transportation Infrastructure, was recognized as one of top 16 projects in the country and was managed by Dr. Venkiteela. The Principal Investigator for the study was Dr. Matthew Bandelt from the New Jersey Institute of Technology (NJIT) and championed by NJDOT’s Bureau of Materials.
Transportation infrastructure systems must resist conditioning from the natural environment and physical demands from service loading to meet the needs of users across the state. Reinforced concrete, which is widely used in bridge decks, pavements, super- and substructures, and other systems, deteriorates under environmental conditioning due to electro-chemical processes that cause expansive mechanics stresses at various length scales (e.g., reinforcement corrosion, freeze-thaw, etc.), leading to costly and timely durability and maintenance challenges.
The project report, which provides a background on the state-of-the-art of advanced reinforced concrete materials that are being investigated to improve reinforced concrete transportation infrastructure. A series of experimental and numerical research activities were then carried out to assess the mechanical properties and long-term durability of these systems. Results show benefits across a range of metrics and have the potential to substantially improve the in-service behavior of reinforced concrete transportation infrastructure.
Methods to preheat an excavated pothole prior to repair were described to improve the interface bonding between existing pavements and hot filling material.
The second project, Innovative Pothole Repair Materials and Techniques, was recognized in the Maintenance, Management, and Prevention supplemental categories and was also managed by Dr. Venkiteela. Separate research reports were prepared for asphalt (Volume I) and concrete structures (Volume II). The Principal Investigator for the study was Dr. Hao Wang from Rutgers-Center for Advanced Infrastructure and Transportation.
Pothole repair is one of the most important and frequent maintenance activities for highway agencies. Significant amounts of costs and resources are spent in pothole repair for material, labor, equipment, and traffic control. Cost-effective pothole repair methods can reduce or eliminate the possibility of re-patching and save future repair costs. The good condition of pothole repair with less cracking will also prevent reflective cracking when asphalt overlay is placed. Preheating the excavated pothole prior to repair has been found to improve the interface bonding between existing pavements and hot filling material, which can help enhance the overall performance of asphalt patches.
The long lifespan of a durable patch will reduce travel delay due to work zone and safety risk of highway users and workers. They will better preserve the condition of highway infrastructure and provide better service to the traveling public. The feasible usage of recycled materials can reduce the production of new material, which can contribute towards a more sustainable approach of roadway repair with economic and environmental benefits.
Additional information about the research teams for each research project and links to Final Reports, Technical Briefs, and select presentations given at the NJDOT Research Showcase or at Lunchtime Tech Talk can be found in the resources section below.
Resources
Bandelt, Matthew J., Matthew P. Adams, Hao Wang, Husam Najm, Andrew Bechtel, Seyed Masoud Shirkorshidi, and Jin Fan. Advanced Reinforced Concrete Materials for Transportation Infrastructure. No. FHWA NJ-2023-003. New Jersey. Department of Transportation. Bureau of Research, 2023. Final Report. Retrieved here.
Bandelt, Matthew J., Matthew P. Adams, Hao Wang, Husam Najm, Andrew Bechtel, Seyed Masoud Shirkorshidi, and Jin Fan. Advanced Reinforced Concrete Materials for Transportation Infrastructure. No. FHWA NJ-2023-003. New Jersey. Department of Transportation. Bureau of Research, 2023. Technical Brief. Retrieved here.
Lunchtime Tech Talk! Webinar: Advanced Reinforced Concrete Materials for Transportation Infrastructure. Webinar. Presentations by Matthew Bandelt and Matthew Adams. Retrieved here.
Wang, Hao, and Xiao Chen. “Innovative Pothole Repair Materials and Techniques Volume I: Asphalt Pavement.” (2024). Final Report. Retrieved here.
Wang, Hao, and Xiao Chen. Innovative Pothole Repair Materials and Techniques Volume I: Asphalt Pavement. (2024). Technical Brief. Retrieved here.
Najm, Husam, Bala Balaguru, Hao Wang, Hardik Yagnik, and Alissa Persad. “Innovative Pothole Repair Materials and Techniques Volume II: Concrete Structures.” (2024). Final Report. Retrieved here.
Asphalt Pavement Pothole Repair with Recycled Material and Preheating. Presentation at NJDOT Research Showcase by Xiao Chen and Hao Wang, Retrieved here (Presentation) and here (Recording).
The New Jersey Department of Transportation’s Bureau of Research, Innovation and Information Transfer (BRIIT) invites you to share your research and innovation ideas on the NJ Transportation Ideas Portal.
We seek to fund RESEARCH IDEAS that lead to implementation – to the testing and adoption of new materials and technologies, to better specifications and to greater efficiency. We strive to discover and advance feasible solutions for more durable infrastructure, greater environmental protection and resilience, and improved mobility and safety for residents, workers and visitors.
We encourage you to suggest INNOVATION IDEAS that advance deployment of innovations and knowledge transfer in transportation. We work with the New Jersey State Transportation Innovation Council (NJ STIC) whose mission is to identify, evaluate, and where possible, rapidly deploy new technologies and process improvements that will accelerate project delivery and improve the quality of NJ’s transportation network. Innovation Ideas will be vetted for next steps which might include research or supporting an initiative to deploy a new technology or process improvement to accelerate innovation.
WHO CAN SUBMIT IDEAS? NJDOT’s research customers and other interested transportation practitioners are encouraged to submit a research or innovation idea. The portal should be of interest to NJDOT, NJ TRANSIT and MPOs, and county and local governments, and other transportation subject matter experts from university, industry and trade organizations and other NGOs. The portal is also open to the public.
WHO ARE RESEARCH CUSTOMERS? Subject matter experts from NJDOT, NJ TRANSIT, or the NJ Motor Vehicles Commission are often our research customers. Research ideas typically must have a champion among our research customers. Ideally, a “champion” is a responsible individual within a division, bureau or unit who is prepared to sponsor or advance a research idea from its inception to study completion.
COLLECTING IDEAS NOW! Our research and innovation teams review submitted ideas for possible funding and other actions throughout the year. The last day to submit research ideas for the next round of funded transportation research is December 31, 2024.
Our research and innovation teams review submitted ideas for possible funding and other actions throughout the year.
REGISTER TO PARTICIPATE AND SUBMIT AN IDEA. Once you are registered, you may submit ideas at any time. Click on the “+”button at the top of the page to submit an idea after registering. Only registered participants may submit a new idea or vote on other ideas to show your support. Register at the NJ Transportation Ideas here: https://njdottechtransfer.ideascale.com/
Concrete production is energy intensive, and requires materials that are both challenging, and expensive to acquire. Material engineers are seeking alternative materials that are more cost-effective and carbon-friendly, but also operate successfully as road and building material.
We spoke with Alyssa Yvette Sunga, a graduate researcher at Rowan University who won the Best Student Poster Award at NJDOT’s 2023 Research Showcase. Her research, “Properties of Cementitious Materials with Reclaimed Cement,” evaluated the characteristics of cementitious materials mixed with varying percentages of reclaimed cement. Sunga and her fellow researchers examined each mixture’s initial setting time, heat of hydration and compressive strength and compared it against ordinary Portland cement. The purpose: to determine if adding reclaimed cement has any effect on the durability and use of cementitious materials. If there is little to no adverse effect, reclaimed cement may help reduce the need for new materials and can reduce the carbon bi-product of concrete. Dr. Shahriar Abubakri (Shah), Ms. Sunga’s supervisor at Rowan University, also joined us for the interview.
Q. Could you tell us a little bit about your educational and research experience and how you got where you are now as a graduate research fellow at Rowan?
A. I’m an international student from the Philippines. I graduated from the University of the Philippines – Los Banos in 2017 with a Bachelor of Science in Civil Engineering. After that, I worked in industry from 2018 to 2022. My former undergraduate professors, who were graduate students here [at Rowan], reached out to me asking if I was interested in pursuing graduate studies. I applied and began my Master’s in Civil Engineering in January 2023.
Q. What interested you about researching the properties of reclaimed cement? Do you hope to continue research in pavement materiality?
A. The environmental impact of reclaimed materials like cement is interesting to me. Cement production is a significant contributor to carbon emissions, so finding ways to reuse it is essential. Additionally, reclaimed cement presents unique challenges and opportunities in terms of material properties, durability, and performance.
So, in a way, we’re helping produce less carbon emissions; that’s what interested me about this study.
I’m currently working on a lot of different concrete projects. We’re hoping to develop more efficient construction approaches, but I also aim to contribute to the development of innovative techniques and solutions that will optimize reclaimed materials in construction projects. We also aspire to collaborate with industry partners and government organizations, so that we can implement these sustainable practices on a full-scale project in the future.
Alyssa Sunga received the Best Poster Award for Student Research At the 25th Annual NJDOT Research Showcase in October 2023.
Q. Was there anything particularly noteworthy or surprising to you discovered from this research?
A. Yes, there’s potential for reclaimed cement and enhancing the performance of unsustainable construction materials. We did not expect that we could use it as a replacement cement or as a supplementary cementitious material. Through various experiments, we found that using this reclaimed cement or incorporating it in cementitious mixtures resulted in comparable properties such as durability, strength, and workability.
Q. Your research looked at cement paste and mortar specimens incorporated with up to 20% Reclaimed Cement and found no significant difference for the flow measurement and setting time. Should further research be done with higher percentages of reclaimed cement? Why did your research cap it at 20%?
A. We’re planning to do further research on larger amounts of reclaimed cement. We just used 20% as a cap to get a general idea of the effect of partially replacing ordinary Portland cement with reclaimed cement. Now that our research with 20% is showing good results, we plan on doing tests with higher percentages in the future.
Q. Your research found that cement paste specimens with up to 20% Reclaimed Cement (RC) saw a 4% reduction in compressive strength after 90 days. What does this mean for applicability (i.e. is 4% a significant reduction? does this make cement paste with 20% RC not suitable for pavement?)
A. A 4% reduction may seem small, but it must still be taken into consideration. However, as long as the strength is within a recommended range, then it is suitable for pavement applications.
Q. Is there a percentage of reclaimed cement that is most likely not suitable for pavement?
A. Alyssa: My advisor would like to jump in to answer that.
Shah: The acceptable percentage of reduction in concrete strength depends on the specific application and the assumptions made by the designer. For instance, practical standards like the American Concrete Institute (ACI 301.1.6.6) typically require that the average strength of three samples meets or exceeds the specified compressive strength. Additionally, each individual sample within this set should not fall below 500 psi of the designed strength. It’s important to note that concrete’s compressive strength can vary widely, ranging from 2500 psi to 5000 psi, and even higher in residential and commercial structures. Some applications may require strengths exceeding 10,000 psi. So, in cases where the required strength aligns with the design strength, even higher reductions may be acceptable.
Q. Mortar specimens with 20% RC had a different result and surpassed the strength after 28 days. Why do you think this was a different result from cement paste specimens? What does this mean for applicability?
A. This difference in result may be due to different factors, but mortar differs from cement paste due to the additional materials like sand. So, this can influence the hydration and the strength development, but we still need to do further research to understand the long-term performance and durability or the effect of adding different materials to the cementitious materials.
We still must do further research to see the effects of adding different materials like sand and gravel to cement paste. If we’re going to use it in concrete, that’s another additional material like an aggregate. It’s just a matter of the specific materials. There are a lot of factors — like the temperature where you make your specimens. So, it’s always just trial and error. There’s no trend to it really.
Q. Your poster suggests that incorporating up to 20% RC has some promising benefits including reducing carbon emissions. What are some of the other benefits?
A. Incorporating the 20% RC will help mitigate supply shortages because we’re able to provide an alternative source of material instead of just using cement. It also promotes eco-friendly construction practices, contributing to sustainable transportation infrastructure, and research on reclaimed cement enables ongoing enhancements in material performance and construction methods.
Q. You have mentioned throughout this interview where there’s a need for more research. Can you describe some specific things that you would really like to research about incorporating reclaimed cement into cementitious materials?
A. The most important part of this research is determining what is the optimal mix proportions to use and then studying the effects on fresh properties and assessing the long-term durability like compressive strength, the tensile strength. These investigations are crucial for understanding the full potential of reclaimed cement in construction. Personally, I’m deeply interested in exploring these research areas further.
Q. What kind of impact do you hope this research will have on material selection by transportation agencies?
A. I hope this research convinces transportation agencies to use reclaimed cement in pavements. It’s sustainable, cost effective and performs well — aligning with transportation agencies’ goals and standards. This could lead to a greener and more resilient transportation infrastructure.
Resources
Sunga, A., Abubakri, S., Lomboy, G., Mantawy, I. (2023). “Properties of Cementitious Materials with Reclaimed Cement”. Rowan University Center for Research & Education in Advanced Transportation Engineering Systems. Poster.
Biometric sensors have long been used in cognitive psychology to measure the stress-level of individuals. These sensors can measure a variety of human behaviors that translate as stress: the movement of eyes, stress-induced sweat, and heart rate variability. Recently, this research strategy has moved beyond psychology and into disciplines like transportation planning, to provide an alternative approach to researching micromobility and stress.
We spoke with Dr. Wenwen Zhang, associate professor at the Edward J. Bloustein School of Planning and Public Policy at Rutgers University, about her experience learning about and using biometrics for a micromobility study. Dr. Zhang’s research, “Rider-Centric Approach to Micromobility Safety” examines the stress levels of micromobility users as they transverse a varied path through an urban space.
Q. How is your research funded?
A. Funding comes from multiple sources. The first source is a seed grant from the Rutgers Research Council which supports an interdisciplinary pilot project. Through this grant, we purchased biometric sensors and hired students to conduct a literature review and develop a research design. We also processed the collected pilot data and paid for participation incentives under this funding. I presented preliminary findings from this study, Rider-Centric Approach to Micromobility Safety, at the 2023 NJDOT Research Showcase. At the time that I presented it, I had 24 samples. The presentation ended up inspiring several people who attended the Research Showcase to volunteer as participants—which increased the sample size to 30.
Our other source of funding came from an external grant from the C2Smart University Transportation Center (UTC) at NYU. We used this resource to support obtaining additional stress sensors, data analysis, cleaning, preprocessing, and modeling, as well as collecting more sample data for the E-scooter and bicycle experiments.
Q. How did you get interested in using biometrics sensors (e.g., eye tracking glasses, galvanic skin sensor, heart rate monitors) to study micromobility safety? How does this research differ from your past work?
A. Before I used biometric sensors, most of my work used passive travel behavior data. For example, to determine the revealed preferences of mode and route choices and risk factors, we used travel trajectory or existing crash big data to develop statistical models. I have found that the entire process is very passive, especially since we only explore risk factors after traffic accidents. It’s surprising that in the research field today we know so little about how human beings actually navigate urban environments while using different travel modes and how it relates to perceived safety. I wanted to explore questions like what is their gaze behavior? How do they feel while they travel using different modes? How do they feel traveling on roads with different design features and how is that going to influence their travel satisfaction or experience overall?
Dr. Robert Noland, Distinguished Professor at the Rutgers Bloustein School, suggested I investigate the use of biometrics in planning studies. As I dug more into the literature, I realized that biometrics in transportation is a very fascinating topic that I wanted to get into. Once I did experiments in the field, I realized that I really enjoyed talking with different people about how they perceive the built environment while they travel. Biometrics provide richer data compared with revealed preference data that I used to work with.
Q. In your research, you noticed that some corridors were more stress-inducing (according to biometric sensors) than expected, despite properly designed safety infrastructure. How do you think this discovery may affect how planners and engineers look at urban road design and micromobility safety?
A. This study collected one-time cross-sectional data. We asked people to walk around an area and tell us whether they feel stressed or not. If they are feeling stress, even in the presence of a safety improvement, it does not necessarily mean that the implemented safety design is not working. For example, in New Brunswick, we observed that a lot of people found it stress-inducing to cross Livingston Avenue, although it has been the subject of a road diet and has several pedestrian safety features incorporated into the new design. While outside our scope of research, one way to understand the impact of the safety infrastructure would be to conduct a “before” and “after” study. This leaves an opportunity for more research, to see how effective the pedestrian-only infrastructure is in reducing stress level. Potentially, it can provide evidence to support pedestrian-only design. Biometric sensors used in a “before and after” study can help us to answer which infrastructure is more preferred.
Q. You are in the process of collecting data for cyclists and e-scooters using the same method, what are your principal objectives in addressing this segment? Do you expect the results to be different?
Dr. Zhang conducted one pilot e-scooter experiment at Asbury Park, NJ in 2022 to test out the devices and examine how to set up research experiments. She equipped the e-scooter rider, Dr. Hannah Younes, post-doc researcher at the Rutgers Bloustein School, with an eye tracking glass, a GSR sensor on the hand, and a 360-degree camera on top of the helmet.
A. Yes, absolutely, different travel modes will likely alter a person’s expectation for a safe travel environment. For example, we noticed a big difference in the enjoyment of pedestrians and e-scooters on the same path through a park. We had thought that the e-scooter users would enjoy the ride as the pedestrians had, however, the pavement was too rough for the small wheels of the e-scooters. Although the park was walking-friendly, it was not friendly for e-scooters. This shows that each of these micromobility modes needs different kinds of support to feel safe and comfortable.
Q. What are the limitations to this study? Do you have plans for future research to address this? How would you like to expand your research in this topic?
A. Each of the biometric sensors has limitations. For example, eye trackers face some difficulty when identifying the pupils of a participant in direct sunlight. As a result, the eye tracker renders a low eye tracking rate. Eye trackers also work better with darker eyes as the eye movements are more readily recognized. The eye trackers, kept on glasses, also restrict individuals who wear glasses from participating. The unfortunate result of this is that it often excludes a lot of senior people from the experiment. This issue may be alleviated as we are obtaining additional funding to obtain prescription lenses for eye trackers.
GSR sensors use low voltage on skin to measure skin conductivity, which may interfere with electric health devices. This limits individuals from participating if they have an electric health device like a pacemaker on or in their body. We purposefully excluded this population from participating to align with IRB (Institutional Review Board) protocol and to mitigate any risks.
Another limitation of the study is that we must collect sample data one by one, which is a time-consuming process. We can only collect a very small sample compared to a traditional statistical model kind of study, which may have access to thousands of records in the sample. From our literature review, biometrics sensor studies typically involve 20 to 30 participants, but for each participant we have a very rich dataset. For each participating volunteer, we end up with over one gigabyte of data. The limited number of participants may make it harder to generalize results to the entire population, and people may question the results applicability. In some ways this data is similar to the results of qualitative studies, where we have richer information but small sample size, rendering some generalizability issues.
Feelings of safety were measured using the traditional self-report survey as well as biometric trackers like Heart Rate Trackers, Eye trackers and GSR (pictured above).
Q. What challenges have you found in working with biometrics sensors, or in the interpretation of output measures?
A. Theeye tracker and heart rate measures are reliable, but some biometrics have posed challenges. The GSR (galvanic skin response sensor), which tests your sweat level, is very sensitive to humidity and time of the day. The sensor also picks up on sweat resulting from physical exertion, making it difficult to distinguish between stress-induced sweat and physical sweat.
Interpretation of output measures for this metric requires data cleaning and processing to eliminate the effect of sweating from physical exertion. We try to decompose the data to separate the emotional peak from the sweating caused by physical activity using various algorithms. We are still underway testing out different algorithms to clean up the data. So far, we have found that GSR data are very real-time in nature and a good indicator for stress level but are very noisy data and requires some manual processing. This means we spend a lot of time preprocessing the collected data before conducting data analysis.
Q. How do you expect this research to inform transportation agencies in New Jersey and elsewhere?
A. This type of research captures such rich data on travel behavior itself. Most of the literature using biometrics has been focused on driving, so this research expands the perspective. Here we’re focusing on slow mobility, like active travel and micromobility. Individuals who participate in slow mobility are more vulnerable road users, and we want to see how they behave in different travel environments. This can help agencies gain more insights into how to design safety infrastructure. Beyond that I can also envision the technology being used to evaluate whether certain improvements or infrastructure designs help to improve travel satisfaction or improve people’s experience at the same location by doing “before and after” studies. This type of study also allows you to measure and quantify the effect of the improvement.
The use of biometric sensors in the field can also be used to foster meaningful public engagement processes to show the lived experience of different people in a neighborhood or traveling through a different corridor, which can be very powerful.
Q. Do you feel the research methods are at a stage where they are “ripe” for use on other demonstration projects, planning or project development studies?
A. After one year of experimentation, our project team can readily work with biometrics. We have a good understanding of sensor limitations and how to set up the sensors to correctly reduce noise as much as possible. Our experience has also helped determine what kind of metrics can be extracted successfully and reliably through the sensors.
The most useful case for those sensors is to evaluate before and after, so that we can quantify how much people appreciate those implementations in a more accurate way. Beyond that, the sensors can also be effective infrastructure assessment tools. For example, imagine that you ask people to wear biometric sensors and do a bicycle infrastructure evaluation; the agencies can get more realistic and rich data compared with a more traditional survey approach. This rich data can help determine the most effective improvement. It ends up being more inclusive that way.
The tools can be very useful for fostering community engagement with vulnerable populations. For example, if agencies want to improve the accessibility for wheelchair users, they can ask individuals in wheelchairs to wear the sensors and move about an area. Recording and reviewing how they experience a journey is more powerful compared with just asking individuals with needs about their travel patterns. It’s going to be a more straightforward way to show the world how we can make the streets more inclusive for those vulnerable populations.
Q. Do you think local governments and non-governmental organizations could make use of biometrics sensors as a strategy to promote community engagement and outreach to local communities, or to address specific community safety or livability issues? Would it be cost-prohibitive to employ such tools for such community-based planning issues at this time?
A. From my point of view, the most effective way would be for the agencies to identify where there are needs and promising projects and then work with skilled researchers or practitioners who have these sensors already and have begun to climb the learning curve in the use of sensors and interpretation — for example, they could work with us. They would need to pay for the researchers’ time and participation incentives, or if they were to collaborate with a UTC (University Transportation Center) to conduct such research collaboratively.
The sensors are not the most expensive part of the study. The most expensive item is the researcher’s time to collect and analyze the data. The data are very complicated to analyze in the first place because it’s a large amount of data with noises. The researchers need to put in a lot of time to get it to the state where you can extract the relevant variables out and start to interpret them.
Q. How would you characterize the “state-of-training” in using biometrics for students or early career or mid-career professionals in transportation?
A. The biometric sensor itself is not very new, but new to the transportation field, especially for slow modes. It has been widely used in cognitive psychology, where there are classes to interpret those as well. Generally, I don’t think the current transportation and urban planning curriculum for students includes enough classes to cover those sensors. We probably need to teach not only biometric sensors, but urban sensing in general.
In an ideal course, students could get their hands dirty by putting those sensors in the field and then once the data are collected, they can learn how to preprocess and analyze the data. It would have to be a one-year kind of curriculum design to get people involved and ready for it. Of course, instruction on the use of sensors will differ by topic. For example, if you are working in the air quality field, then there are many different air quality sensors and each of them come with different data formats and require different experiment design and analytic skills.
Regarding the mid-career transportation professional, at this moment I believe the research is more in the academic field and focusing on testing and evaluation. I wouldn’t suggest that the research is so ripe that a mid-career transportation or urban planner professional should need to invest their time in learning how to use biosensors unless they have a research project that may benefit substantially from using the sensors.
Resources
To learn more about the use of biometrics in the field of active transportation, see:
Ryerson, M., Long, C., Fichman, M., Davidson, J.H., Scudder, K.N., Kim, M., Katti, R., Poon, G. & Harris, M., (2021). Evaluating Cyclist Biometrics to Develop Urban Transportation Safety Metrics. Accident Analysis & Prevention, Volume 159, 2021. Retrieved from https://www.sciencedirect.com/science/article/pii/S0001457521003183?via%3Dihub
Fitch, D.T., Sharpnack, J. & Handy, S. (2020). Psychological Stress of Bicycling with Traffic: Examining Heart Rate Variability of Bicyclists in Natural Urban Environments. Transportation Research Part F: Traffic Psychology and Behavior, Volume 70, 2020, Pages 81-97. Retrieved from https://www.sciencedirect.com/science/article/pii/S1369847819304073?via%3Dihub.
Zhang. W. 25th Annual NJDOT Research Showcase. Recording starts at: 59:00. Retrieved from https://youtu.be/D_rQP-Dv8gU
Zhang, W., Buehler, R., Broaddus, A. & Sweeney, T. (2021). What Type of Infrastructures do E-scooter Riders Prefer? A Route Choice Model. Transportation Research Part D: Transport and Environment, Volume 94, 2021. Retrieved from https://www.sciencedirect.com/science/article/pii/S1361920921000651.
For more information about the use of biometrics in the broader transportation field, see NYU’s C2SMART’s research project on Work Zone Safety:
The State of New Jersey has advanced policies, programs, and projects such as complete streets that encourage greater transportation modal choice and less dependency on the single-occupancy vehicle to address climate change and promote mobility and access for all users. The NJ Statewide Bicycle and Pedestrian Master Plan and Complete Streets policy seek to increase connectivity and micromobility safety through road diets and other infrastructure changes. New Jersey Department of Transportation (NJDOT) is also sponsoring safety programs that aim to reduce traffic related fatalities. In-depth research that looks at differences across gender, race, socioeconomic status and ability may assist in expanding policies and statewide initiatives that prioritize safety and accessibility for all road users.
This Q&A article has been prepared following an interview with Dr. Hannah Younes, a post-doctoral researcher at the Alan M. Voorhees Transportation Center at Rutgers University, who focuses on cyclists and e-scooter behavioral patterns. Her most recent study conducted in Asbury Park, NJ observed gender differences of chosen micromobility mode, helmet usage, and location. We interviewed her to better understand the data sources and methods used in the research, its limitations and explore the applicability and implications of her research findings to the field of transportation and future research. The Q&A interview has been edited for clarity.
Q. How was your research funded?
This work was supported by the National Science Foundation under a grant called “Making Micromobility Smarter and Safer”. The lead on this is Dr. Clint Andrews at Rutgers University and there are several other principal investigators. My study acts as a part of this multi-year research.
Q. Can you share a brief overview of your findings? Are the results surprising or unique compared to past research?
We are one of the only studies comparing the safety behavior of cyclists and e-scooter users across genders. Without considering gender, we found that one-third of cyclists wore a helmet. We also found in our observations that e-scooter users did not wear a helmet. It speaks to how important it is to have safe micromobility infrastructure, especially knowing that people are unlikely to wear a helmet. In the U.S., even if you give everyone a helmet, they’re probably not going to wear it. That’s just how it is. Keeping people safe in other ways is paramount.
The temporary bike lane created as a part of Dr. Younes research. Asbury Park, NJ
We also found that a greater proportion of women were using e-scooters than bicycles. This is important because cycling has long been a male-dominated mode of transportation, for a variety of reasons. That is true across the world. There are studies that suggest women are less likely to cycle to work because of clothing like wearing a skirt or dress or heels, or fears of sweating. E-scooters remove that hurdle since they are not as prohibitive in terms of clothing and require less physical exertion. So, the vehicle type itself may make a difference. Moreover, women place more importance on bike lane infrastructure than men. If we are seeing that e-scooters are the preferred mode for females, perhaps e-scooters can help narrow the gender gap in micromobility.
Q. Can you talk a little bit about the methods used for this study? How are these methods different from past research? Why did you choose to use traffic cameras for your observations?
This work was done using manual observations, a common method in micromobility studies. Previous research had used observations collected in the field. Instead of having observers in the field, we observed traffic camera footage at one intersection. Because we were observing gender and race as well as group behavior, the footage was useful as it allowed us to pause when needed. It was also less resource intensive than having a person stand in the field since no travel expenses were associated with the analysis.
Q. What challenges have you found in working with and interpreting traffic camera footage? With the improvement of AI technologies, do you think there will be an opportunity to automate this process in the future? Are there any limitations you expect from this type of innovation?
It is very time consuming and tedious to analyze this much camera footage. We analyzed 35 hours of footage. I would love to have analyzed more, but you have to draw the line somewhere depending on the resources available for the research or project study. Most of the time, we fast forwarded until a micromobility user was detected, but it still requires undivided attention. There is a possibility with current technology to incorporate AI technologies: to use computer vision to detect humans, which then can be manually viewed by a human to assess micromobility mode, gender, and helmet use. This would likely reduce the manual labor… It would be interesting to compare the computer vision model to the work I have done… Nonetheless, computer vision does not differentiate properly between pedestrians and e-scooter users, so it is prone to misidentification, which would lengthen the time taken to observe manually.
The view from the intersection traffic camera. Asbury Park, NJ
At this point, computer vision cannot detect gender, helmet use, and group riding properly from traffic camera footage. More high-resolution images would be needed to differentiate gender and helmet use (like unobstructed face images) and group riding requires context clues like making eye contact, waiting for one another, etc. AI has the potential, but it is not there yet. As time consuming as it is, I am confident that we detected every person, which is why we chose to observe the footage ourselves.
Q. What are the limitations of this study? Do you have plans for future research to address these? How would you like to expand your research on this topic?
The main limitation is the geographical scope of this research; it’s a lot of work for one city. We only analyzed the behavior of micromobility in one location, Asbury Park. It isn’t clear how much the results will translate from one location to another. Mode of transportation and behavioral use depends on many different factors that vary from location to location. There is evidence that the gender gap is smaller for e-scooter users in Brisbane, Australia, but not to the extent observed in Asbury Park. Same goes with helmet use. A larger scale study would be useful. Other limitations include the types of micromobility modes: we only observed shared e-scooters and privately owned bicycles in Asbury Park. So, we’re comparing two different vehicles and two different share types to one another. When analyzing the data, we must consider both of these factors. For example, are behaviors attributed solely to the vehicle or to the share type? Probably both. When you’re looking at the gender gap, is it because it’s an e-scooter or is it because it’s shared that there is a narrower gender gap?
An analysis comparing shared and privately owned e-scooters with shared and privately owned bicycles would be great. Differentiating between e-bikes and bicycles would be great too, although the resolution of traffic camera footage makes it very hard to differentiate between the two. Even with an observer onsite, it would be hard to detect, so you would need a survey, but this could alter behavior. In Asbury Park, a lot of people have privately owned e-scooters now, so we could do another study in 1.5-2 years and get additional insights in the same location.
E-bikes are a growing mode of transportation, but even with traffic camera footage, it is very hard to tell an e-bike apart from a bicycle, so maybe in that case you would need somebody on site actually observing. You’re losing the ability to pause footage, but it might be more useful if you’re looking at e-bikes. Race and age were also very difficult to observe from the footage. It could be easier if someone was in person to observe in addition to the traffic camera footage. Even then, without asking directly the age and race/ethnicity of the user, there will be bias. There are a lot of different things to consider; it really depends on what the question is.
Q. How would you like this research to inform transportation agencies and practitioners in New Jersey and elsewhere?
There are several key points. Users of shared e-scooters and privately owned bicycles are different and behave differently. E-scooter users are more likely to take risks like not wearing a helmet or riding on the road. Planners must ensure that the infrastructure keeps them safe. That is, implementing dedicated protected bike lanes that are connected to a greater network and adding traffic calming measures to slow the speeds of motor-vehicles like raised crosswalks or narrower traffic lanes.
Understanding the reasons behind lane use is important as well, as there are concerns for pedestrian safety. Our research observed that lane use was different; for example, 7 percent of male cyclists rode on the sidewalk, compared to 28 percent of female e-scooter users.
Additionally, having a shared e-scooter system in a city can increase female participation in micromobility use. It is a more gender equitable mode than bicycles. Other agencies might want to implement an e-scooter share program in their town.
Q. Your research shows that women were more likely than men to ride on the sidewalk while using an e-scooter or bike. Given that this strategy is illegal in most parts of the country, how can planners, engineers and policymakers use this information to increase feelings of safety for female micromobility users?
This is really interesting. From my research, there is not a lot that I could say. Implicitly, one of the reasons for someone to ride on the sidewalk instead of the road is that they feel safer on the sidewalk. There is a need to ensure that micromobility users feel just as safe on the road–that is, implement a dedicated and protected bike lane, and provide a clear separation from motor-vehicles.
From our work, we know that there are other more complex factors at play: our research had clear results for road lane use with the implementation of the bike lane, but less clear ones for sidewalk use: sidewalk use was not significantly reduced by the presence of a pop-up bike lane. To encourage safe road use, ensuring a complete network would be a start. The pop-up bike lane was not connected to another bike lane going downtown, for instance. If you’re already coming downtown on the sidewalk, you might be more likely to stay there given the existing curb that would need to be crossed to go from the sidewalk to the pop-up bike lane.
Representation of bidirectional bicycle lanes Image via Streetmix. Ensuring cyclists and e-scooter users have safe infrastructure as shown above is important for all road users’ safety.
Q. NJDOT is sponsoring a program to ensure the implementation of the Statewide Bicycle and Pedestrian Master Plan. In what ways could this master plan or a future one align with the findings in your study?
The results of this study reinforce that implementing a bike lane provides a layer of safety for micromobility users. Nearly all the increase in bike lane usage came from a reduction in traffic lane usage, not in sidewalk usage. There is so much research out there that shows that bike lanes save lives; in the case of a crash, someone in a bike lane is less likely to be injured. Ensuring that plans accommodate both bicycles and e-vehicles–like e-bikes and e-scooters–is also paramount.
Q. The Biden Administration has set a goal to achieve a net zero emissions economy by 2050. How might a shift toward micromobility help the nation reach its climate and carbon emission goals?
Bicycles are zero emission vehicles. E-bikes and e-scooters produce few emissions, especially privately owned ones since they don’t require rebalancing. Rebalancing shared vehicles requires a car or van and those gasoline emissions are absorbed by those shared e-scooters. Having an e-vehicle do that for rebalancing helps to reduce those emissions. Bicycle-friendly infrastructure, which reduces motor-vehicle infrastructure such as the number of traffic lanes, or parking, can also reduce motor-vehicle use and induce more environmentally friendly travel.
Q. How could a focus on reaching these climate goals impact the way that planners and engineers design streets?
Motor-vehicle travel is the most polluting transportation mode. A shift towards micromobility Infrastructure, particularly in cities, can help induce travel from eco-friendly modes and reduce motor-vehicle use. This should be in conjunction with other measures, such as increasing gasoline prices, increasing parking costs, and providing subsidies for eco-friendly modes.
Marshall, H. (2023). “How do Female Cyclists Perceive Different Cycling Environments? – A Photo-elicitation study in Stockholm, Sweden.” Retrieved from https://gupea.ub.gu.se/handle/2077/78209
This Research to Implementation video presents an example of NJDOT-sponsored research and the effect such research has in addressing transportation-related issues within the State.
Pervious (or porous) concrete has been gaining popularity as a potential solution to reduce the amount of impermeable surfaces associated with sidewalks, reduce puddling, and potentially slow storm water surface runoff. As important as these benefits are to surface runoff mitigation, concerns exist as to the ability of pervious concrete to provide sufficient structural support and longevity for the expected service life of the sidewalks as well as its life cycle costs. The composition of pervious concrete can limit its mechanical strength and present challenges in its maintenance to achieve the expected service life.
The Research to Implementation video series promotes the benefits of funded research to increase the safety of the traveling public, reduce costs, and increase efficiency.
The New Jersey Department of Transportation’s (NJDOT) Bureau of Research invites you to share your research and innovation ideas on the NJ Transportation Ideas Portal.
We seek to fund RESEARCH IDEAS that lead to implementation – to the testing and adoption of new materials and technologies, to better specifications and to greater efficiency. We strive to discover and advance feasible solutions for more durable infrastructure, greater environmental protection and resilience, and improved mobility and safety for residents, workers and visitors.
We encourage you to suggest INNOVATION IDEAS. We seek to find strategies to advance deployment of innovations and knowledge transfer in transportation. We work with the New Jersey State Transportation Innovation Council (NJ STIC) whose mission is to identify, evaluate, and where possible, rapidly deploy new technologies and process improvements that will accelerate project delivery and improve the quality of NJ’s transportation network. Innovation Ideas will be vetted for next steps which might include research or supporting an initiative to deploy a new technology or process improvement to accelerate innovation.
WHO CAN SUBMIT IDEAS? NJDOT’s research customers and other interested transportation practitioners are encouraged to submit a research or innovation idea. The portal should be of interest to NJDOT, MPOs, county and local governments, and other transportation subject matter experts from university, industry and trade organizations and other NGOs. The portal is also open to the public.
WHO ARE RESEARCH CUSTOMERS? Subject matter experts from NJDOT, NJ TRANSIT, or the NJ Motor Vehicles Commission are often our research customers. Research ideas typically must have a champion among our research customers. Ideally, a “champion” is a responsible individual within a division, bureau or unit who is prepared to sponsor or advance a research idea from its inception to study completion.
COLLECTING IDEAS NOW! Our research and innovation teams review submitted ideas for possible funding and other actions throughout the year. The last day to submit research ideas for the next round of funded transportation research is December 31, 2023.
Our research and innovation teams review submitted ideas for possible funding and other actions throughout the year.
REGISTER TO PARTICIPATE AND SUBMIT AN IDEA. Once you are registered, you may submit ideas at any time. If you registered previously, you should not need to register again. Click on the “+”button at the top of the page to register. Only registered participants may submit a new idea or vote on other ideas to show your support. Register at the NJ Transportation Ideas here: https://njdottechtransfer.ideascale.com/
A recently completed research study on NJ TRANSIT grade crossing safety focuses on identifying locations for rail grade crossing elimination. Researchers from Rutgers’ Center for Advanced Infrastructure and Transportation (CAIT), Asim Zaman, P.E., Xiang Liu, Ph.D., and Mohamed Jalayer, Ph.D., from Rowan University, developed a methodology using 20 criteria to narrow a list of 100 grade crossings to ensure appropriate identification for closure. The process helps NJ TRANSIT and New Jersey Department of Transportation (NJDOT) to direct limited funds to areas of greatest need to benefit the public.
Across the country, 34 percent of railroad incidents over the past ten years have occurred at grade crossings. The elimination of grade crossings can improve public safety, decrease financial burdens, and improve rail service to the public.
According to the proposed methodology, the 20 crossings recommended for closure located in Monmouth County (60%), Bergen County (25%), and Essex County (25%).
The researchers ranked grade crossings in New Jersey using the following data fields: crash history, average annual daily traffic, roadway speed, roadway lanes, length of the crossing’s street, weekday train traffic, train speed category, number of tracks, access to train platforms, intersection angle, distance to alternate crossings, distance to emergency and municipal buildings, whether emergency and municipal buildings are on the same street, and date of last or future planned signal and surface upgrades. This process resulted in a final list of 20 grade crossings eligible for elimination.
To understand how this study will be used, we conducted an interview with NJTRANSIT personnel Susan O’Donnell, Director, Business Analysis & Research, Ed Joscelyn, Chief Engineer – Signals, and Joseph Haddad, Chief Engineer, Right of Way & Support.
Q. How will the report inform decision-making?
It is important to have solid research and strong evaluation criteria, such as developed by this study, on which to base decisions for grade crossing elimination. In addition to the study, we looked at what other state agencies and transit agencies have done with grade crossing elimination, as well as criteria recommendations from Federal Highway Administration (FHWA) and Federal Railroad Administration (FRA). Following up on this study, NJ TRANSIT and NJDOT are considering next steps that would be needed to close the 20 identified grade crossings. In New Jersey, the Commissioner of Transportation has plenary power over the closing of grade crossings.
Q. What other information will be needed to assess these locations?
Local concerns about grade crossing elimination tend to focus on traffic re-routing, including the possible impacts on neighborhoods, time needed to reach destinations, and emergency vehicle access to all parts of a community. The criteria established by the study addressed these areas of concern. Prior studies have determined that the road networks around the identified locations are adequate to accommodate re-routed traffic. The current research study took into account the findings from those prior studies. As each project moves forward, NJDOT will determine if additional information will be needed.
Q. Is elimination of any of these grade crossings part of NJ TRANSIT’s capital program?
All of the closings are part of the capital program. Funding for the grade crossing elimination comes from the federal government and NJ TRANSIT. NJ TRANSIT funding is in place to close the crossings.
Q. Are there benefits of the research study beyond identification of the 20 grade crossings?
The research study developed the criteria and process for identifying grade crossings for elimination. This framework can be used in the future to assess other grade crossings for possible elimination. NJ TRANSIT is grateful to NJDOT for funding this important research project to improve safety.
For more information on this research study, please see the resources section below.
The New Jersey Department of Transportation’s (NJDOT) Bureau of Research invites you to share your ideas on the NJ Transportation Research Ideas Portal. We are asking NJDOT’s research customers and other transportation stakeholders to propose research ideas for the NJDOT Research Program. Join us in finding workable solutions to problems that affect the safety, accessibility, and mobility of New Jersey’s residents, workers, visitors and businesses.
REGISTER TO PARTICIPATE. Once you are registered, you may submit ideas at any time. If you registered previously, you should not need to register again. Click on the “+”button at the top of the page to register.
HOW DO I SUBMIT AN IDEA? Only registered participants can log in to submit a new idea or vote on other ideas to show your support. Register at the NJ Transportation Research Ideas here: https://njdottechtransfer.ideascale.com/
NEXT ROUND OF RESEARCH. Submit your research ideas no later than December 31, 2022 for the next round of research RFPs. The NJDOT Research Oversight Committee (ROC) will prioritize research ideas after this date, and high priority research needs will be posted for proposals.
