Identifying the safety factors over traffic signs in state roads using a panel quantile regression approach

Abstract

Objective: This study intended to investigate the interactions between accident rate and traffic signs on state roads located in Croatia and accommodate the heterogeneity attributed to unobserved factors. Data from 130 state roads between 2012 and 2016 were collected from Traffic Accident Database System maintained by the Republic of Croatia’s Ministry of the Interior.

Methods: To address the heterogeneity, a panel quantile regression model was proposed, in which a quantile regression model offers a more complete view and a highly comprehensive analysis of the relationship between accident rate and traffic signs, and the panel data model accommodates the heterogeneity attributed to unobserved factors.

Results: Results revealed that (1) low visibility of material damage (MD) and death or injury (DI) increased the accident rate; (2) the number of mandatory signs and the number of warning signs were more likely to reduce the accident rate; (3) the average speed limit and the number of invalid traffic signs per kilometer exhibited a high accident rate.

Conclusions: To our knowledge, this study is the first attempt to analyze the interactions between accident consequences and traffic signs by employing a panel quantile regression model; by including visibility, the present study demonstrates that low visibility causes a relatively higher risk of MD and DI. It is noteworthy that average speed limit positively corresponds with accident rate; the number of mandatory signs and the number of warning signs are more likely to reduce the accident rate; and the number of invalid traffic signs per kilometer is significant for the accident rate; thus, regular maintenance should be performed for a safer roadway environment.

Keywords:

• Accident rate
• heterogeneity
• panel data
• panel quantile regression model
• quantile regression

Acknowledgment

The authors are grateful for data collection from the Republic of Croatia Ministry of the Interior.

Data availability statement

Accident data from the Traffic Accident Database System that support the findings of this study are available from the Ministry of the Interior of the Republic of Croatia (http://stari.mup.hr/1261.aspx). Traffic signs data that support the findings of this study are available from Prof. Darko Babic (email: dbabic@)fpz.hr) at the University of Zagreb, Croatia, upon reasonable request.

Additional information

Funding

The study was jointly supported by the National Road Safety Program of the Republic of Croatia 2011–2020, Fundamental Research Fund for the Central Universities (HUST: 2017KFYXJJ140 and 2018KFYYXJJ001), and Singapore Ministry of Education Academic Research Fund Tier 1 (MOE2017-T1-001-069).