Calibration of Highway Safety Manual Predictive Models for Oregon State Highways

Xie, Fei; Gladhill, Kristie; Dixon, Karen; Monsere, Christopher M.

doi:10.3141/2241-03

Cited by 68 publications

(34 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Shortly after the release of the HSM, Xie et al calibrated the HSM models for the state of Oregon with the method outlined in the HSM (1). The calibration calculations resulted in factors consistently below the expected value of 1.0, an outcome that was likely attributed to Oregon's property damage only crash self-reporting procedures and its higher property damage only reporting thresholds compared with the states that were used in developing the HSM crash proportions (1).…”

Section: Calibration Effortsmentioning

confidence: 97%

Strength of the Variable

Troyer

Bradbury

Juliano

2015

Transportation Research Record: Journal of the Transportation R

View full text Add to dashboard Cite

In Part C, the HSM presents a predictive crash analysis method that is based on a series of statistical models called "safety performance functions" (SPFs). SPFs are regression models developed from observed crash data that predict the average crash frequency of a roadway on the basis of a set of geometric and traffic conditions. Annual average daily traffic (AADT), segment length, or both serve as explanatory variables, where applicable. The predictive power of SPFs can provide extremely useful information for departments of transportation (DOTs) and other agencies for purposes of funding, project planning, and other applications. However, the HSM SPFs were developed with data from select states across the United States; thus these predictions are not always accurate for all jurisdictions. With the calibration of the HSM models, the SPFs can be adjusted to better predict safety performance for these specific areas.The Ohio DOT desired to incorporate the HSM procedures into its project development process, beginning initially with its Highway Safety Improvement Program and design exception processes. To facilitate these actions, it was necessary to calibrate the provided SPFs for all roadway types currently covered in the HSM for the state of Ohio or develop jurisdiction-specific SPFs. Because developing unique, agency-specific SPFs is a labor-intensive and more difficult task, the Ohio DOT elected first to develop calibration factors and test the fit of the adjusted SPFs to assess whether the calibration factors were sufficiently reliable to be used for predictive analyses. If not, Ohio-specific SPFs could be developed for select roadway facility types that were identified for improvement. Calibration EffortsWhile more states and jurisdictions are beginning to look into developing agency-specific information, whether for calibration factors or full SPFs, there are not many studies that consider evaluating calibration factors before developing SPFs. Shortly after the release of the HSM, Xie et al. calibrated the HSM models for the state of Oregon with the method outlined in the HSM (1). The calibration calculations resulted in factors consistently below the expected value of 1.0, an outcome that was likely attributed to Oregon's property damage only crash self-reporting procedures and its higher property damage only reporting thresholds compared with the states that were used in developing the HSM crash proportions (1).Comparing the fit of calibrated and uncalibrated models is a common approach across multiple agencies around the United States. Srinivasan et al. compared the mean error of the precalibration results with the postcalibration results for the Florida DOT (2). The study also created agency-specific SPFs and compared them with the calibrated HSM SPFs. The findings indicated that the calibrated The AASHTO Highway Safety Manual (HSM) provides methods for departments of transportation (DOTs) and other agencies to incorporate high-quality quantitative safety analyses into project development and decision m...

show abstract

Section: Calibration Effortsmentioning

confidence: 97%

Strength of the Variable

Troyer

Bradbury

Juliano

2015

Transportation Research Record: Journal of the Transportation R

View full text Add to dashboard Cite

show abstract

“…In particular, the HSM predictive method was assumed as a benchmark by several studies, which calibrated it for different areas [42][43][44][45][46][47][48]. Some of them clearly concluded that locally-derived functions fits better data than the calibration of other functions.…”

Section: Transferability Of Predictive Methodsmentioning

confidence: 99%

Integrated American-European protocol for safety interventions on existing two-lane rural roads

Colonna

Intini

Berloco

et al. 2017

Eur. Transp. Res. Rev.

View full text Add to dashboard Cite

Purpose The main purpose was to integrate two strategies for road safety analyses (qualitative: audits, inspections; and quantitative: accident predictions) and develop a possible protocol for the safety interventions on existing two-lane rural road segments. Those road sections do not typically belong to the TEN-network, to which the 2008/96/EC Directive is mainly oriented. Hence, they could lack of methods for designing safety-based interventions. The main research questions were:& Which possible problems can arise from the application of this protocol to real cases? & Which data are practically needed? & Which possible solutions can be provided for the highlighted problems?Methods The integrated protocol, including: 1) the HSM predictive method, 2) the EU Regulations, 3) the local road design standards, 4) some research developments; is applied to real two-lane rural road segments requiring safety-based interventions. Its application is divided in the typical road safety analysis stages. Results A wide list of possible problems was highlighted and addressed: 1) lack of data, 2) difficult comparison with current road standards in order to identify safety problems, 3) lack of methods for evaluating the skidding risk along the layout, 4) setting speed limits, 5) need for optimizing the selection of countermeasures based on their aims and their timely application, in different recurrent situations, 6) availability and comparison of predictive methods.Conclusions Based on the problems and solutions discussed, main advantages (1) the systematic approach, 2) the quantitative assessment of benefits, 3) the possible transferability) and disadvantages (difficulties in overcoming the lack of data and calibrated accident prediction models) of the method were remarked.

show abstract

“…Calibration factors are the third component of the HSM predictive method. Numerous researchers have updated the calibration factors for their respective jurisdictions (Banihashemi, 2011;Fitzpatrick, Schneider, & Carvell, 2006;Mehta, & Lou, 2013;Persaud, Lord, & Palmisano, 2002;Shin, Lee, & Dadvar, 2014;Sun, Magri, Shirazi, Gillella, & Li, 2011;Xie, Gladhill, Dixon, & Monsere, 2011). Researchers have found that calibration factors may vary not only across different parts of a region, but also based on geometric characteristics (for instance, tangent versus horizontal curve segments) (Fitzpatrick, Schneider, et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Updating the Crash Modification Factors and Calibrating the IHSDM for Indiana

Tarko¹,

Romero²,

Hall³

et al. 2018

View full text Add to dashboard Cite

The Interactive Highway Safety Design Model (IHSDM) is a tool for assessing the safety impact of project-level design decisions by implementing the HSM crash prediction methodology. Safety Performance Functions (SPFs), Crash Modification Factors/Functions (CMFs), calibration factors, and crash proportions are utilized in predicting the number, severity, and type of crashes occurring on various types of roadway facilities. This study updated and expanded the set of CMFs applicable to Indiana conditions for various geometric, traffic, pavement, and other road characteristics. CMFs for 80 various road and control improvements for urban and rural segments, intersections, and interchanges. This report also presents the methodology of calibrating the IHSDM's predictive components based on local data and past research. This method jointly estimates the SPFs and CMFs to preserve the crash prediction consistency. SPFs, CMFs, and crash proportions were calibrated for Indiana rural two-lane segments, rural divided multilane segments, and urban/suburban arterial segments. Example calculations showed that some results were only slightly affected while others vary considerably. This finding confirms the need for calibrating the parameters in the IHSDM to local conditions.

show abstract

Calibration of Highway Safety Manual Predictive Models for Oregon State Highways

Cited by 68 publications

References 2 publications

Strength of the Variable

Strength of the Variable

Integrated American-European protocol for safety interventions on existing two-lane rural roads

Updating the Crash Modification Factors and Calibrating the IHSDM for Indiana

Contact Info

Product

Resources

About