Journal of Transportation Research

Journal of Transportation Research

“Evaluating the Impact of Intelligent Transportation Systems on Traffic Safety Using Poisson and Negative Binomial Models: A Case Study of the Ramsar–Gorgan National Highway”

Document Type : Original Article

Authors
Esfandiar Heidari Kani 1
Ali Naderan 2
1 Ph.D., Candidate, Department of Civil Engineering, SR.C., Islamic Azad University, Tehran, Iran.
2 Assistant Professor, Department of Civil Engineering, SR.C., Islamic Azad University, Tehran, Iran.
10.22034/tri.2026.570070.3428
Abstract
Intelligent Transportation Systems (ITS) are widely recognized as effective interventions for improving road safety. This study evaluates the impact of ITS components, including speed enforcement cameras, Variable Message Signs (VMS), and Weigh-In-Motion (WIM) systems, on crash frequency along high-traffic road corridors in Mazandaran and Golestan provinces. A six-year dataset (2013–2018) comprising 16,669 reported crashes, annual average daily traffic (AADT), and detailed spatial information on ITS installations was analyzed. Poisson and Negative Binomial regression models were employed to model crash frequency as count data. The results indicate that speed cameras have a statistically significant crash-reduction effect, particularly within short distances from installation sites, with substantial reductions observed across most model specifications. In contrast, WIM systems were associated with an increase in crash frequency, especially in close proximity to their locations. This finding is attributed to abnormal driving behavior and sudden maneuvers by some heavy vehicle drivers attempting to disrupt or evade system operation. Model comparison results show that the Negative Binomial model provides a better fit than the Poisson model, indicating the presence of overdispersion in the crash data. Overall, the findings suggest that proper deployment and management of ITS—especially automated enforcement cameras—can significantly enhance road safety. However, effective implementation of WIM systems requires redesign, driver training, and enhanced monitoring. Policy and operational recommendations are provided to improve ITS performance.
Keywords
Traffic Safety
Before–After Analysis
Intelligent Transportation Systems (ITS)
Regression Models
Subjects
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