| Summary: | 碩士 === 國立交通大學 === 運輸與物流管理學系 === 105 === Freeway safety issue has long been considered as the top priority to be improved because accidents not only cause serious losses of involved parties but also induce excessive traffic delays. Therefore, numerous studies have dedicated to investigate the key factor contributing to accidents and propose effective countermeasures accordingly. However, few studies examine the potential risk of work zone on crashes. Work zone may block lanes and interrupt traffic flow, causing potential risk to crashes. Based on this, this study aims to investigate the effects of work zone on crash frequency and severity.
To do so, this study adopts Poisson regression (PO) and Negative Binomial (NB) models to investigate the effects of work zone on crash frequency and Ordered Probit (OB) model to examine the effects of work zone on crash severity, respectively. Various types of work zones according to the number of lanes blocked and during daytime or nighttime are classified. The frequency model uses of a collective approach to aggregate crashes and types of work zone (number or occupancy) over a certain length of segments (three different lengths, 1, 2, and 3 km, are compared in this study) over a year; while the severity model uses of an individual approach to investigate the effect of work zone on crash severity individually.
A case study based on the crash data of Taiwan No.-1 Freeway and work zone data of Southern Region Engineering Office of Taiwan Area National Freeway Bureau is conducted. The result estimation results show that the number of work zones significantly affects crash frequency, especially, the effect vary across types of work zones. The work zones blocking one lane in the daytime tend to increase the number of crash, comparing to those blocking more than one lane; however, work zones in the nighttime increase higher risk to drivers no matter how many number of lanes occupied. As to the effect of work zone on crash severity, the estimation shows most of work zone types may lower down crash severity levels, due to the lower travel speed in the work zone area. At last, countermeasures are then proposed accordingly.
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