Level of Service of Safety: Conceptual Blueprint and Analytical Framework

2003 ◽  
Vol 1840 (1) ◽  
pp. 57-66 ◽  
Author(s):  
Jake Kononov ◽  
Bryan Allery
Keyword(s):  
Conceptual Development ◽  
Analytical Framework ◽  
Level Of Service ◽  
Specific Level ◽  
Performance Function ◽  
Safety Problem ◽  
Safety Performance Function ◽  
Highway Safety Manual ◽  
Accident Frequency ◽  
Annual Average Daily Traffic

While some initial and significant progress has been made in the development of a highway safety manual, much remains to be done in the areas of conceptual development and the diagnostics of safety problems. The concept of level of service of safety (LOSS) in the framework of safety performance function is introduced, and the problem of diagnostics is addressed. LOSS reflects how the roadway segment is performing in regard to its expected accident frequency and severity at a specific level of annual average daily traffic. It provides a comparison of accident frequency and severity only with the expected norms; it does not, however, provide any information related to the nature of the safety problem itself. If the safety problem is present, LOSS will describe only its magnitude. The nature of the problem is determined through diagnostic analysis by direct diagnostics and pattern recognition techniques, which are also discussed.

Two Problems of Averaging Arising in the Estimation of the Relationship Between Accidents and Traffic Flow

1998 ◽  
Vol 1635 (1) ◽  
pp. 37-43 ◽  
Author(s):  
Abraham Mensah ◽  
Ezra Hauer
Keyword(s):  
Traffic Flow ◽  
Annual Average ◽  
Performance Function ◽  
Safety Performance Function ◽  
Time Period ◽  
Annual Average Daily Traffic ◽  
Averaging Problem ◽  
Long Time ◽  
The Relationship ◽  
The Ideal

A function linking the expected accident frequency to traffic flow is called a safety performance function (SPF). SPFs are estimated from data for various facilities and accident types. Typically, accident counts over a period of a year or more, and estimates of average flow for such periods, serve as data. The ideal is for SPFs to represent cause-effect regularities. However, because accident counts are for a long time period and because average flows are used, two issues of averaging arise. First, the cause-effect relationship is between accidents and the flows prevailing near the time of accident occurrence. Therefore, ideally, these should be the argument of the SPF. In practice, however, either because of lack of detail or difficulties of estimation, average flows are used for estimation. The question is what problems arise when average flows, such as annual average daily traffic, instead of the flows at the time of the accident are used as the argument of the SPF. This is the argument averaging problem. Second, there are at least two (daytime and nighttime) and perhaps many more cause-effect SPFs that prevail in the course of a year. Ideally, each relationship should be estimated separately. The question is what problems arise if one joint SPF is estimated when two or more separate functions should have been used. This is the function averaging problem. After analysis, how to account and how to correct for the argument averaging problem are shown. At this time, avoiding the function averaging problem by estimating daytime and nighttime SPFs separately can be the only recommendation.

scholarly journals Calibration of highway safety manual predictive models and validation of safety performance funtions for canadian urban/suburban intersections

2021 ◽  
Author(s):  
Shahzad Faisal
Keyword(s):  
Predictive Models ◽  
Safety Performance ◽  
Local Data ◽  
Performance Function ◽  
Safety Performance Function ◽  
Highway Safety Manual ◽  
Related Aspect ◽  
Crash Types ◽  
The City ◽  
Collision Models

In this research, the HSM predictive models for collisions on urban/suburban arterials are calibrated for collision data from the City of Toronto. It has been found that the use of calibration factors for applying HSM models to Toronto intersection data is not appropriate. New collision models are therefore developed by using local data. The HSM and Toronto models are then calibrated to City of Edmonton intersection collision data to determine whether it is better to calibrate HSM models for a Canadian jurisdiction or models from another Canadian jurisdiction. A related aspect of the research is the investigation of models for crash types. There is no safety performance function (SPF) available in the HSM to predict rear end collisions. Instead, rear end collisions are estimated as a proportion of predicted multivehicle collisions. To overcome this deficiency, Toronto data are used in the estimation of models for rear end collisions.

Identifying Locations with Potential for Accident Reductions: Use of Direct Diagnostics and Pattern Recognition Methodologies

2002 ◽  
Vol 1784 (1) ◽  
pp. 153-158 ◽  
Author(s):  
Jake Kononov
Keyword(s):  
Pattern Recognition ◽  
Safety Performance ◽  
Performance Function ◽  
Safety Performance Function ◽  
Lighting Conditions ◽  
Road Section ◽  
Annual Average Daily Traffic ◽  
Safety Performance Functions ◽  
Pattern Recognition Analysis ◽  
The Many

Safety performance functions reflect the complex relationship between exposure, usually measured in annual average daily traffic, and accident count for a unit of road section over a unit of time. One of the main uses of the safety performance functions is to identify locations that experience more accidents than expected, thus exhibiting a potential for accident reduction. Overrepresentation in the number of accidents above the expected or normal threshold predicted by the safety performance function is only one of many indicators of a potential for accident reduction. Accident type, severity, road condition, spatial distribution of accidents, and lighting conditions are only a few of the many important symptoms of the accident problem. Two methodologies are introduced for identification of locations with potential for accident reduction: direct diagnostics and continuous pattern recognition analysis. Use of these methodologies revealed that existence of accident patterns susceptible to correction may or may not be accompanied by the overrepresentation in accident frequency detected by the safety performance functions.

scholarly journals Calibration of highway safety manual predictive models and validation of safety performance funtions for canadian urban/suburban intersections

2021 ◽  
Author(s):  
Shahzad Faisal
Keyword(s):  
Predictive Models ◽  
Safety Performance ◽  
Local Data ◽  
Performance Function ◽  
Safety Performance Function ◽  
Highway Safety Manual ◽  
Related Aspect ◽  
Crash Types ◽  
The City ◽  
Collision Models

In this research, the HSM predictive models for collisions on urban/suburban arterials are calibrated for collision data from the City of Toronto. It has been found that the use of calibration factors for applying HSM models to Toronto intersection data is not appropriate. New collision models are therefore developed by using local data. The HSM and Toronto models are then calibrated to City of Edmonton intersection collision data to determine whether it is better to calibrate HSM models for a Canadian jurisdiction or models from another Canadian jurisdiction. A related aspect of the research is the investigation of models for crash types. There is no safety performance function (SPF) available in the HSM to predict rear end collisions. Instead, rear end collisions are estimated as a proportion of predicted multivehicle collisions. To overcome this deficiency, Toronto data are used in the estimation of models for rear end collisions.

Evaluation of Safety Performance Functions Based on Experimental Design Using a Cross-Validation Method

2017 ◽  
Vol 2636 (1) ◽  
pp. 62-72 ◽  
Author(s):  
Jung-Han Wang ◽  
Mohamed A. Abdel-Aty ◽  
Jaeyoung Lee
Keyword(s):  
Goodness Of Fit ◽  
Cross Validation ◽  
Safety Performance ◽  
Major Road ◽  
Highway Safety Manual ◽  
Annual Average Daily Traffic ◽  
Minor Road ◽  
Safety Performance Functions ◽  
The One ◽  
Leave One Out

The Highway Safety Manual (HSM) Part C provides a series of safety performance functions (SPFs) for different roadway conditions. The SPFs suggested in the HSM are formulated on the basis of exposure variables: the logarithms of the annual average daily traffic (AADT) on the major road and on the minor road under the base condition. In this research, data from 7,802 intersections in Florida were collected and processed. These intersections were categorized into seven types based on area type (rural or urban), number of legs (three or four), and number of approaches controlled by stop signs. Twenty-two SPF formulations, including the one suggested by the HSM, were developed for each intersection type for examination of the goodness-of-fit measures of the SPFs. In addition, the goodness of fit of each model of the 22 SPFs in each category was examined with 10-fold leave-one-out cross-validation (LOOCV). With a comparison of the delta values generated with the LOOCV method, it is suggested that the SPF with the logarithm of the total entering vehicle volume and the ratio of the AADT on the minor road and the AADT on the major road are important. In addition, the SPFs with the AADT on the major road and the AADT on the minor road and their logarithmic transformations are also important. Therefore, it is suggested that the future HSM compare these two SPF formulations—as suggested in the current research, along with the original SPF formulation in the manual—and select the one with the best model fit on the basis of the delta value using LOOCV.

scholarly journals Elaborating a systems methodology for cascading climate change impacts and implications

2021 ◽  
Author(s):  
NA Cradock-Henry ◽  
J Connolly ◽  
P Blackett ◽  
Judith Lawrence
Keyword(s):  
Climate Change ◽  
Conceptual Development ◽  
Climate Change Impacts ◽  
Analytical Framework ◽  
Expert Elicitation ◽  
Future Climate Change ◽  
Visual Aids ◽  
Systems Methodology ◽  
Human Environment ◽  
New Research

New research is drawing attention to the potential for climate change to generate cascading impacts and implications across linked human-environment systems, requiring closer accounting of these interactions to anticipate the emergence of surprises and feedbacks. However, there is little practical guidance for those interested in characterising, identifying or assessing cascades, and few empirical examples. In this paper, we elaborate a systems-based methodology to identify and evaluate cascading climate change impacts and implications. We illustrate its application using the case of a participatory process with urban infrastructure managers, facing the legacy effects of damaging earthquakes and the prospect of future climate change. The results show the proposed approach and visualisation of cascades as causal diagrams provides a robust and flexible analytical framework. The use of systems thinking, visual aids, interactive discussion and expert elicitation generated valuable information about potential cascades, their interactions across domains of interest, and the implications for management. The process can provide a basis for further empirical application and advance methodological and conceptual development. Specifically, the systems methodology: • Identifies interdependencies and interconnections which may serve as transmission pathways for climate-related impacts; • Enhanced stakeholders’ understanding of multiple causes and effects of climate change; and • Produced a useful visual aid for stakeholders to explore cascading impacts and implications, and opportunities for intervention.

scholarly journals Analysis of Space Usage on Train Station Platforms Based on Trajectory Data

2020 ◽  
Vol 12 (20) ◽  
pp. 8325
Author(s):  
Mira Küpper ◽  
Armin Seyfried
Keyword(s):  
Waiting Times ◽  
Time Of Day ◽  
Level Of Service ◽  
Trajectory Data ◽  
Specific Level ◽  
Train Station ◽  
Flow Profiles ◽  
Realistic Assessment ◽  
The Times ◽  
Measurement And Evaluation

The functionality of railway platforms could be assessed by level of service concepts. They describe interactions between humans and the built environment and allow one to rate risks due to overcrowding. To improve existing concepts, a detailed analysis of how pedestrians use the space was performed, and new measurement and evaluation methods are introduced. Trajectories of passengers at platforms in Bern and Zurich Hardbrücke (Switzerland) were analysed. Boarding and alighting passengers show different behaviour, considering the travel paths, waiting times and mean speed. Density, speed and flow profiles were exploited and a new measure for the occupation of space is introduced. The analysis has shown that it is necessary to filter the data in order to reach a realistic assessment of the level of service. Three main factors should be considered: the time of day, the times when trains arrive and depart and the platform side. Therefore, density, speed and flow profiles were averaged over one minute and calculated depending on the train arrival. The methodology developed in this article is the basis for enhanced and more specific level of service concepts and offers the possibility to optimise planning of transportation infrastructures with regard to functionality and sustainability.

How the choice of safety performance function affects the identification of important crash prediction variables

2016 ◽  
Vol 88 ◽  
pp. 1-8 ◽  
Author(s):  
Ketong Wang ◽  
Jenna K. Simandl ◽  
Michael D. Porter ◽  
Andrew J. Graettinger ◽  
Randy K. Smith
Keyword(s):  
Safety Performance ◽  
Performance Function ◽  
Crash Prediction ◽  
Safety Performance Function
Sign in / Sign up

Export Citation Format

Share Document