Introduction
With the expansion of road transport networks and the increasing development of various types of vehicles, there has been a rise in people’s need and desire to travel for access to goods, services, and better living conditions. This increase in mobility has led to heightened traffic and congestion on many urban and rural roads across the country. A major challenge facing traffic planners, road transport authorities, traffic police, rescue, and emergency medical services, as well as drivers and passengers, is the high incidence of road accidents. These accidents can result in human casualties, injuries, disabilities, economic losses, and social damages. This issue is particularly pressing in regions like Mazandaran Province, which attracts numerous tourists daily due to its natural beauty and busy roads. Haraz Road, providing the shortest route from Tehran to Mazandaran and featuring key natural attractions like Damavand Mountain, experiences heavy traffic and frequent road accidents. This study aimed to analyze the spatial and temporal distribution patterns of road accident density using the kernel density estimation (KDE) method, identify accident-prone zones through acute point analysis, and explore the spatial and temporal variability of accident clusters on the tourist-heavy Haraz Road. 

Method
The data used for this analysis was collected over five years (2016-2020) by the Red Crescent Society of Iran in Mazandaran Province. 

Results 
The results indicated that during this period, 742 accidents occurred on Haraz Road, resulting in 1,538 injuries and 91 fatalities. The decrease in the number of accidents from 2018 to 2020 may reflect the impact of COVID-19-related restrictions on traffic and road transportation. Additionally, the seasonal distribution of road accidents shows a higher frequency in spring and summer compared to other seasons on Haraz Road. An examination of the density distribution pattern of road accidents using the kernel density estimation (KDE) method from 2016-2020 revealed spatial-temporal variability in accident density along different sections of Haraz Road. During this period, the stretch from Punjab to Kahrud-e Pain was identified as the most hazardous part of Haraz Road, exhibiting the highest accident density. An analysis of the annual trend in accident density highlighted that in 2015, the areas of Kahrud-e Pain, Gaznak, and Pleur were recognized as the most dangerous. In subsequent years, only Kahrud-e Pain continued to show the highest density of accidents, while Gaznak and Pleur experienced medium to low accident densities. Furthermore, the KDE results indicated that between 2016 and 2020, approximately 8 km of Haraz Road had high to very high accident density. In the same timeframe, around 7 km of the road had an average accident density, and over 90 km of the road was estimated to have low to very low accident density. In addition to the results from the kernel density estimation (KDE) function, hot spot analysis from 2016 to 2020 also identified four critical accident-prone areas along Haraz Road in Punjab, Kahrud-e Pain, Gaznak, and Pleur. These areas exhibited spatial clusters of accidents with a Z-score of 4.49, indicating a confidence level between 90% and 99%. The segments of Haraz Road within these clusters, totaling 6 km in length, accounted for 42% of the accidents recorded continuously over the five years. An examination of the spatio-temporal patterns in the analysis of these acute points revealed a decreasing trend in the number of spatial accident clusters, the percentage of continuous accidents, and the length of road affected within the identified clusters from 2016 to 2020. This trend may be linked to the COVID-19 pandemic and associated travel restrictions from 2019 to 2020. 

Conclusion
The findings from this research can assist in identifying factors contributing to road accidents in areas with high accident densities and where spatial accident clusters are present. The identified high-risk areas along Haraz Road should draw attention from organizations involved in traffic and road transport, traffic police, and rescue stations, as well as from travelers themselves. This awareness is crucial for implementing necessary measures to enhance road and travel safety. Furthermore, the results can be leveraged for crisis management of road accidents, helping to develop preventive strategies to reduce accident occurrences, prepare for potential accidents, and provide essential services to possible victims. 

Ethical Considerations

Compliance with ethical guidelines
The ethical principles observed in the article.

Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors.

Authors' contributions
Study design, methodology and data interpretation: Jalal Samia; Data collection and implementing a part of the research method: Manouchehr Ranjber Shoubi; Final revision: Amer Nikpour.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
The authors are extremely grateful to the Red Crescent Rescue Organization of Mazandaran Province for providing the statistics of road accidents in Haraz Axis.




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