Explorative Analysis of Motorcyclists’ Injury Severity Pattern at a National Level in Iran

Document Type : Original Article


1 Department of Transportation Engineering, School of Civil Engineering, Iran University of Science and Technology, 2Road Safety Research Center, Iran University of Science and Technology, Tehran, Iran

2 Department of Transportation Engineering, School of Civil Engineering, Iran University of Science and Technology

3 1Department of Transportation Engineering, School of Civil Engineering, Iran University of Science and Technology, 2Road Safety Research Center, Iran University of Science and Technology, Tehran, Iran



Objectives: This study aimed at examining the hidden patterns of motorcycle crashes and riders’ injury severity at the national level in
Iran. Methods: Hierarchical clustering (HC) and latent class clustering (LCC) techniques were used in combination to analyze riders’ injury
pattern in 6638 motorcycle crashes occurred in Iran during 2009–2012. First, the HC was performed to classify the provinces into homogeneous
groups, based on the percentage of different crash factors in each province and a new variable called “province group” was added to the crash
database as the output of the HC analysis. Next, the LCC was conducted to cluster the crash data and to investigate the riders’ injury pattern
across the country. Results: Among the six crash clusters identified by the LCC, Clusters 1 and 5, in which, respectively, 91% and 84%, of the
riders were under 30 as well as Cluster 2, in which 65% of the riders were above 30 years had the highest percentages of injured motorcyclists
(86%, 84%, and 88%, respectively). Cluster 5 had also the lowest percentage of helmet usage (about 5%) and licensed riders (5%). Moreover,
Cluster 6 had the highest fatality rate among the six clusters. In this cluster, 73% of the crashes were occurred in nonresidential/agricultural
land uses, and 94% were occurred in rural areas. Conclusions: Since a significant share of crashes in Cluster 5 was occurred in province
Groups C and E; this might be regarded as an indication of weak law enforcement over helmet usage and licensure in these provinces. In
addition, as the pattern of helmet usage was different among province clusters, future studies might be conducted regarding motorcyclists’
helmet‑wearing intentions among several provinces. Moreover, crashes occurred in rural roads, particularly in the vicinity of nonresidential
or agricultural land uses were more severe and need special future attention.


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