施工區域對高速公路事故頻次與嚴重度之影響

Abstract

高速公路的安全性議題長期以來都受到關注與重視，由於事故之發生不但容易造成人員傷亡外，同時也會造成嚴重的交通延滯。有鑑於此，已有許多研究致力於分析事故成因，並提出有效之改善策略;然而，施工區域對事故的潛在影響卻鮮少被納入考量。其特性在於會佔據車道、干擾車流行進方向，進而提高發生事故之風險。基此，本研究旨在探討施工區域對於事故頻次與嚴重度之影響。

本研究分別建立卜瓦松迴歸模式與負二項迴歸模式，模化施工與事故頻次之關聯性，並利用次序普羅比模式衡量施工對事故嚴重度之影響。此外，依照封閉車道之數目以及作業之時段如白天或夜間作為施工的分類依據。頻次模式係以總體的觀點建立，將路段以等距離分段法切割(本研究共分為三種路段長度，分別為1公里、2公里及3公里，並進行比較)，綜整該年中各路段的事故件數與各施工類別之件數(或佔有率)並予以分析。另一方面，嚴重度模式則係以個別事故案件為單位，探討施工的出現對於事故嚴重度之影響。

本研究係以中山高速公路之事故相關資料及南區工程處所提供之施工通報資料為分析對象。頻次模式的推估結果指出施工件數顯著影響事故頻次，並且影響程度會因施工類型而異。日間佔用單車道之施工作業較佔用多車道者容易造成事故件數的增加；然而，夜間施工對於用路人的行車風險更高，無論佔用車道數目之多寡，皆會提高事故頻次。施工區域對於傷亡嚴重度的影響則顯示，多數類型的施工會降低事故的嚴重度，這係由於施工路段的幾何特性造成行車速度降低，因此發生於該路段的事故件數雖會增加但往往較為輕微。最終，本研究據推估結果研提相關改善措施與建議。

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.