THE MODELS OF ACCIDENT SIZE COMPARISONS BETWEEN INTERCITY MOTORWAY ROUTES

Intercity motorways in Thailand play an important role in national development, as they link
various industrial zones and main harbors for transporting goods abroad. Furthermore, they
connect national tourist attractions. When considering the trend of accident occurrences on
motorways, it has been found that the severity of accident trend has leaned forwards to be on the
continuous increase. This research attempts to establish guidelines for reducing the severity of
accidents on motorways number 7 and number 9 in Thailand; thus, the differences between the two
motorways were considered. This research used and analyzed data from 2010 to 2016 from the
Intercity Motorway Division, Department of Highways. As the severity of injuries cannot be
directly measured, the number of minor injuries, serious injuries, and deaths, as well as the
number of vehicles involved in each accident, were chosen for analysis using structural equation
modeling ( SEM) . Subsequently, a multiple group analysis was used to analyze the differences
between the two models. The results of the factor analysis revealed significantly different severities
of injuries. For motorway number 7 , the traffic flow factor mostly affected accident size, followed
by the road factor and the environmental factor, respectively. For motorway number 9, only
surrounding and road factors affected accident size.