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Observational Before-After Studies in Road Safety

01 Feb 1997-
TL;DR: In this paper, a three part monograph includes: the essentials; adaptations of conventional approaches; and elements of a new approach, which enables road safety researchers and professionals to interpret correctly the results of one of the main sources of knowledge about road safety engineering measures.
Abstract: Enables road safety researchers and professionals to interpret correctly the results of one of the main sources of knowledge about the effect of road safety engineering measures, the "observational Before-After study". This three part monograph includes: the essentials; adaptations of conventional approaches; and elements of a new approach.
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Journal ArticleDOI
TL;DR: In the absence of detailed driving data that would help improve the identification of cause and effect relationships with individual vehicle crashes, most researchers have addressed this problem by framing it in terms of understanding the factors that affect the frequency of crashes -the number of crashes occurring in some geographical space (usually a roadway segment or intersection) over some specified time period as mentioned in this paper.
Abstract: Gaining a better understanding of the factors that affect the likelihood of a vehicle crash has been an area of research focus for many decades. However, in the absence of detailed driving data that would help improve the identification of cause and effect relationships with individual vehicle crashes, most researchers have addressed this problem by framing it in terms of understanding the factors that affect the frequency of crashes - the number of crashes occurring in some geographical space (usually a roadway segment or intersection) over some specified time period. This paper provides a detailed review of the key issues associated with crash-frequency data as well as the strengths and weaknesses of the various methodological approaches that researchers have used to address these problems. While the steady march of methodological innovation (including recent applications of random parameter and finite mixture models) has substantially improved our understanding of the factors that affect crash-frequencies, it is the prospect of combining evolving methodologies with far more detailed vehicle crash data that holds the greatest promise for the future.

1,483 citations


Cites background from "Observational Before-After Studies ..."

  • ...For example, some researchers have used traffic flow as a measure of exposure and found the relationship between crashes and traffic flow to be decreasing (Tanner, 1953; Mahalel, 1986; Hauer et al., 1988; Hauer, 1997; Persaud and Nguyen; 1998) implying a potentially contentious finding that the crash risk per unit of exposure becomes smaller as traffic flow increases (Maher et al....

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  • ...…a measure of exposure and found the relationship between crashes and traffic flow to be decreasing (Tanner, 1953; Mahalel, 1986; Hauer et al., 1988; Hauer, 1997; Persaud and Nguyen; 1998) implying a potentially contentious finding that the crash risk per unit of exposure becomes smaller as traffic…...

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Journal ArticleDOI
TL;DR: A methodology using Geographical Information Systems (GIS) and Kernel Density Estimation to study the spatial patterns of injury related road accidents in London, UK and a clustering methodology using environmental data and results from the first section in order to create a classification of road accident hotspots are presented.

576 citations

Journal Article
TL;DR: The relationship between speed and road safety is a highly controversial and emotionally charged subject as discussed by the authors, and the effects of changes in speed on the number of road accidents or road accident victims are investigated.
Abstract: The relationship between speed and road safety is a highly controversial and emotionally charged subject This report investigates the effects of changes in speed on the number of road accidents or road accident victims It is found that the relationship between speed and accidents or accident victims can be represented by a set of power functions, as postulated in the so called "Power Model" of the relationship between speed and road safety

453 citations


Cites background from "Observational Before-After Studies ..."

  • ...It has therefore been decided to focus on the following four potentially confounding variables that are known (Hauer 1997) to be important in road safety evaluation studies:...

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  • ...Simulation studies made by Hauer (2003) have confirmed this....

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Journal ArticleDOI
TL;DR: The empirical Bayes (EB) method addresses two problems of safety estimation: it increases the precision of estimates beyond what is possible when one is limited to the use of a 2- to 3-year accident history, and it corrects for the regression-to-mean bias.
Abstract: The empirical Bayes (EB) method addresses two problems of safety estimation: it increases the precision of estimates beyond what is possible when one is limited to the use of a 2- to 3-year accident history, and it corrects for the regression-to-mean bias. The increase in precision is important when the usual estimate is too imprecise to be useful. The elimination of the regression-to-mean bias is important whenever the accident history of the entity is in some way connected with the reason why its safety is estimated. The theory of the EB method is well developed. It is now used in the Interactive Highway Safety Design Model and will be used in the Comprehensive Highway Safety Improvement Model. The time has come for the EB method to be the standard and staple of professional practice. The study's goal is to facilitate the transition from theory into practice.

450 citations


Cites methods from "Observational Before-After Studies ..."

  • ...(3), the method is now well developed (1) and has been widely applied....

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Journal ArticleDOI
TL;DR: A multivariate Poisson-lognormal (MVPLN) specification that simultaneously models crash counts by injury severity and non-zero diagonal elements suggests overdispersion in crash counts at all levels of severity is offered.

384 citations


Cites background from "Observational Before-After Studies ..."

  • ...Given the importance of roadways safety, there has been considerable crash prediction research (see, e.g., Hauer, 1986, 1997, and 2001; Abdel-Aty, and Radwan, 2000; Ulfarsson and Shankar, 2003; Kweon and Kockelman, 2000; Lord and Persaud, 2000; Lord et al., 2005; Ma and Kockelman, 2006; Karlaftis…...

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