Thodoris Garefalakis

Mr. Thodoris Garefalakis

National Technical University of Athens, Athens, Attikí, Greece
orcid

Research Focus & Metrics

Academic Career Length

5Years (2022-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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21 November 2024 in European Transport Research Review
Verified
Journal Article
Open access
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TGThodoris Garefalakis
Thodoris Garefalakis
EMEva Michelaraki
Eva Michelaraki
SRStella Roussou
Stella Roussou
CKChristos Katrakazas
Christos Katrakazas
TBTom Brijs
Tom Brijs
GYGeorge Yannis
George Yannis
Road safety is a subject of significant concern and substantially affects individuals across the globe. Thus, real-time, and post-trip interventions have gained significant importance in the past few years. This study aimed to analyze different classification techniques and examine their ability to identify dangerous driving behavior based on a dual-approach study. The analysis was based on the investigation of important risk factors such as average speed, harsh acceleration, harsh braking, headway, overtaking, distraction (i.e., mobile phone use), and fatigue. In order to achieve the objective of this study, data were collected through a driving simulator as well as a naturalistic driving study. To that end, four classification algorithms, namely support vector machines, random forest (RFs), AdaBoost, and multilayer perceptron (MLP) neural networks were implemented and compared. In the simulator experiment, RFs and MLPs emerged as the top-performing models with an accuracy of 84% and 82%, respectively, demonstrating its ability to accurately classify driving behavior in a controlled environment. In the naturalistic driving study, RF and AdaBoost maintained robust performance, with high accuracy (i.e., 75% and 76.76% respectively) and balanced precision and recall. The outcomes of this study could provide essential guidance for practitioners and researchers on choosing models for driving behavior classification tasks.

15 July 2022 in Sensors
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Journal Article
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TGThodoris Garefalakis
Thodoris Garefalakis
Christos KatrakazasChristos Katrakazas
Christos Katrakazas
George YannisGeorge Yannis
George Yannis
Predicting driving behavior and crash risk in real-time is a problem that has been heavily researched in the past years. Although in-vehicle interventions and gamification features in post-trip dashboards have emerged, the connection between real-time driving behavior prediction and the triggering of such interventions is yet to be realized. This is the focus of the European Horizon2020 project “i-DREAMS”, which aims at defining, developing, testing and validating a ‘Safety Tolerance Zone’ (STZ) in order to prevent drivers from risky driving behaviors using interventions both in real-time and post-trip. However, the data-driven conceptualization of STZ levels is a challenging task, and data class imbalance might hinder this process. Following the project principles and taking the aforementioned challenges into consideration, this paper proposes a framework to identify the level of risky driving behavior as well as the duration of the time spent in each risk level by private car drivers. This aim is accomplished by four classification algorithms, namely Support Vector Machines (SVMs), Random Forest (RFs), AdaBoost, and Multilayer Perceptron (MLP) Neural Networks and imbalanced learning using the Adaptive Synthetic technique (ADASYN) in order to deal with the unbalanced distribution of the dataset in the STZ levels. Moreover, as an alternative approach of risk prediction, three regression algorithms, namely Ridge, Lasso, and Elastic Net are used to predict time duration. The results showed that RF and MLP outperformed the rest of the classifiers with 84% and 82% overall accuracy, respectively, and that the maximum speed of the vehicle during a 30 s interval, is the most crucial predictor for identifying the driving time at each safety level.

7 January 2024 in Sustainability
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Journal Article
Open access
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SRStella Roussou
Stella Roussou
TGThodoris Garefalakis
Thodoris Garefalakis
Eva MichelarakiEva Michelaraki
Eva Michelaraki
Tom BrijsTom Brijs
Tom Brijs
George YannisGeorge Yannis
George Yannis
The i-DREAMS project has a core objective: to establish a comprehensive framework that defines, develops, and validates a context-aware ‘Safety Tolerance Zone’ (STZ). This zone is crucial for maintaining drivers within safe operational boundaries. The primary focus of this research is to conduct a detailed comparison between two machine learning approaches: long short-term memory networks and shallow neural networks. The goal is to evaluate the safety levels of participants as they engage in natural driving experiences within the i-DREAMS on-road field trials. To accomplish this objective, the study gathered a series of trips from a sample group consisting of 30 German drivers, 43 Belgian drivers, and 26 drivers from the United Kingdom. These trips were then input into the aforementioned machine learning methods to reveal the factors contributing to unsafe driving behaviour across various experiment stages. The results obtained highlight the significant positive impact of i-DREAMS’ real-time interventions and post-trip assessments on enhancing driving behaviour. Furthermore, it is worth noting that neural networks demonstrated superior performance compared to other algorithms considered within this research context.

20 March 2025 in Sustainability
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Journal Article
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Marios SekadakisMarios Sekadakis
Marios Sekadakis
MSMaria Ioanna Sousouni
Maria Ioanna Sousouni
TGThodoris Garefalakis
Thodoris Garefalakis
MOMaria G. Oikonomou
Maria G. Oikonomou
Apostolos ZiakopoulosApostolos Ziakopoulos
Apostolos Ziakopoulos
George YannisGeorge Yannis
George Yannis
The present study aims to investigate the benefits of eco-driving in urban areas and on highways through an experiment conducted in a driving simulator. Within a group of 39 participants aged 18–30, multiple driving scenarios were conducted, both without and with eco-driving guides, to assess the impact of eco-driving behavior on environmental sustainability and safety outcomes. Data on pollutant emissions, including carbon dioxide (CO2), carbon monoxide (CO), and nitrogen oxides (NOx), as well as crash probability, were collected during the experiment. The relationships between driving behavior and pollutant emissions were estimated using linear regression models, while binary logistic regression models were employed to assess crash probability. The analysis revealed that eco-driving led to a significant reduction in pollutant emissions, with CO2 emissions decreasing by 1.42%, CO by 98.2%, and NOx by 20.7% across both urban and highway environments, with a more substantial impact in urban settings due to lower average speeds and smoother driving patterns. Furthermore, eco-driving reduced crash probability by 90.0%, with urban areas exhibiting an 86.8% higher crash likelihood compared to highways due to higher traffic density and more complex driving conditions. These findings highlight the dual benefit of eco-driving in reducing environmental impact and improving road safety. This study supports the integration of eco-driving techniques into transportation policies and driver education programs to foster sustainable and safer driving practices.

7 December 2023 in Sensors
Verified
Journal Article
Open access
PDF file
SRStella Roussou
Stella Roussou
TGThodoris Garefalakis
Thodoris Garefalakis
Eva MichelarakiEva Michelaraki
Eva Michelaraki
Christos KatrakazasChristos Katrakazas
Christos Katrakazas
MAMUHAMMAD ADNAN
MUHAMMAD ADNAN
George YannisGeorge Yannis
George Yannis
The i-DREAMS project established a ‘Safety Tolerance Zone (STZ)’ to maintain operators within safe boundaries through real-time and post-trip interventions, based on the crucial role of the human element in driving behavior. This paper aims to model the inter-relationship among driving task complexity, operator and vehicle coping capacity, and crash risk. Towards that aim, data from 80 drivers, who participated in a naturalistic driving experiment carried out in three countries (i.e., Belgium, Germany, and Portugal), resulting in a dataset of approximately 19,000 trips were collected and analyzed. The exploratory analysis included the development of Generalized Linear Models (GLMs) and the choice of the most appropriate variables associated with the latent variables “task complexity” and “coping capacity” that are to be estimated from the various indicators. In addition, Structural Equation Models (SEMs) were used to explore how the model variables were interrelated, allowing for both direct and indirect relationships to be modeled. Comparisons on the performance of such models, as well as a discussion on behaviors and driving patterns across different countries and transport modes, were also provided. The findings revealed a positive relationship between task complexity and coping capacity, indicating that as the difficulty of the driving task increased, the driver’s coping capacity increased accordingly, (i.e., higher ability to manage and adapt to the challenges posed by more complex tasks). The integrated treatment of task complexity, coping capacity, and risk can improve the behavior and safety of all travelers, through the unobtrusive and seamless monitoring of behavior. Thus, authorities should utilize a data system oriented towards collecting key driving insights on population level to plan mobility and safety interventions, develop incentives for road users, optimize enforcement, and enhance community building for safe traveling.

16 December 2024 in Infrastructures
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Journal Article
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AAAntonia Antonakaki
Antonia Antonakaki
MOMaria G. Oikonomou
Maria G. Oikonomou
TGThodoris Garefalakis
Thodoris Garefalakis
George YannisGeorge Yannis
George Yannis
The increasing penetration of autonomous vehicles (AVs) presents new challenges and opportunities for road safety. This study aims to evaluate the impact of AV penetration rates on traffic safety through the use of microscopic simulation scenarios based on the Villaverde network in Madrid. Eleven scenarios were simulated with SAE Level 5 AV market penetration rates (MPRs) ranging from 0% to 100% in 10% increments. Vehicle conflicts, defined as instances where the time to collision was less than 1.5 s, were analyzed along with traffic composition and roadway characteristics. Multiple linear and multinomial logistic regression models were applied to examine the relationships between time-to-collision (TTC), conflict numbers, maximum conflict speed, and critical influencing factors such as vehicle type and road capacity. The results indicate that higher AV penetration rates generally improve traffic safety, although the coexistence of conventional vehicles and vehicles equipped with driving automation systems introduces traffic heterogeneity, potentially influencing safety outcomes. These findings suggest that while AVs have a positive effect on road safety, further analysis is needed to address the complexities introduced by mixed-traffic conditions.