Transferability and Calibration of the Highway Safety Manual Performance Functions and Development of New Models for Urban Four-lane Divided Roads PDF Download

Author: Khalid Ahmed Al Kaaf
Publisher:
ISBN:
Category :
Languages : en
Pages : 155

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Moreover, this study examined the calibration of the HSM SPFs for Fatal and Injury (FI), Property Damage Only (PDO) and total crashes for Urban Four-lane divided roadway segments (U4D) in Muscat, Sultanate of Oman and the development of new SPFs. This study first calibrates the HSM SPFs using the HSM methodology, and then new forms for specific SPFs are further evaluated for Muscat's urban roads to identify the best model. Finally, Riyadh fatal and injury model were validated using Muscat FI dataset. Comparisons across the models indicate that HSM calibrated models are superior with a better model fit and would be the best SPFs for predicting collisions in the City of Muscat. The best developed collision model describes the mean crash frequency as a function of natural logarithm of the annual average daily traffic, segment length, and speed limit. The study finds that the differences in road geometric design features and FI collision characteristics between Riyadh and Muscat resulted in an un-transferable Riyadh crash prediction model. Overall, this study lays an important foundation towards the implementation of HSM methods in multiple cities (Riyadh and Muscat), and could help their transportation officials to make informed decisions regarding road safety programs. The implications of the results are extendible to other cities and countries and the region, and perhaps other developing countries as well.

Author:
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ISBN:
Category : Roads
Languages : en
Pages : 123

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"TRB's Transportation Research Record: Journal of the Transportation Research Board, No. 2515, explores 15 papers related to statistical methods and highway safety performance, including: Multivariate Full Bayesian Hot Spot Identification and Ranking: New Technique; Modeling Crash Rates for a Mountainous Highway by Using Refined-Scale Panel Data; Exploring Piecewise Linear Effects of Crash Contributing Factors with a Novel Poisson-Mixed Multivariate Adaptive Regression Splines Model; Classification of Gaps at Uncontrolled Intersections and Midblock Crossings Using Support Vector Machines; Safety Impacts of a Statewide Centerline Rumble Strip Installation Program; Evaluation of the Safety Effectiveness of the Conversion of Two-Lane Roadways to Four-Lane Divided Roadways: Bayesian Versus Empirical Bayes; Is Horizontal Curvature a Significant Factor of Safety in Rural Multilane Highways?; Developing Calibration Factors for Crash Prediction Models with Consideration of Crash Recording Threshold Change; Empirical Bayes Before-After Study on Safety Effect of Narrow Pavement Widening Projects in Texas; Transferability and Calibration of Highway Safety Manual Performance Functions and Development of New Models for Urban Four-Lane Divided Roads in Riyadh, Saudi Arabia; Safety Analysis of Freeway Segments with Random Parameters; Strength of the Variable: Calculating and Evaluating Safety Performance Function Calibration Factors for the State of Ohio; Statistical Evaluation of Different Sample Sizes for Local Calibration Process in the Highway Safety Manual; Results and Lessons from Local Calibration Process of the Highway Safety Manual for the State of Maryland; Validation Technique Applied to Oregon Safety Performance Function Arterial Segment Models." -- Publisher's description

Author: Grant G. Schultz
Publisher:
ISBN:
Category : Bayesian statistical decision theory
Languages : en
Pages : 72

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This report documents the calibration of the Highway Safety Manual (HSM) safety performance function (SPF) for rural two-lane two-way roadway segments in Utah and the development of new models using negative binomial and hierarchical Bayesian modeling techniques. Crash data from 2005-2007 on 157 selected study segments in Utah provided a 3-year observed crash frequency to obtain a calibration factor for the HSM SPF and develop new models. The calibration factor for the HSM SPF for rural two-lane two-way roads in Utah is 1.16, indicating that the HSM underpredicts the number of crashes on these roads by 16 percent. Negative binomial regression was used to develop four new models, and one additional model was developed using hierarchical (or full) Bayesian techniques. The empirical Bayes (EB) method can be applied with each negative binomial model because the models include an overdispersion parameter used with the EB method. The hierarchical Bayesian technique accounts for high levels of uncertainty. Because the hierarchical Bayesian model produces a density function of a predicted crash frequency, a comparison of this density function with an observed crash frequency can help identify segments with significant safety concerns. Each model has its own strengths and weaknesses, which include its data requirements and predicting capability. This report recommends that UDOT use the negative binomial model with transformed average annual daily traffic (AADT) at a 95 percent confidence level (Equation 5-11) for predicting crashes. This model produces accurate results and requires less data than other models. The hierarchical Bayesian process should be used for identifying segments with extreme crash frequencies that may benefit from safety improvements.

Author: Bradford Brimley
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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The study area was the state of Utah. Crash data from 2005-2007 on 157 selected study segments provided a 3-year observed crash frequency to obtain a calibration factor for the HSM SPF and develop new SPFs. The calibration factor for the HSM SPF for rural two-lane two-way roads in Utah is 1.16. This indicates that the HSM underpredicts the number of crashes on rural two-lane two-way roads in Utah by sixteen percent.

Author: Bradford Brimley
Publisher:
ISBN:
Category :
Languages : en
Pages : 84

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Book Description
The study area was the state of Utah. Crash data from 2005-2007 on 157 selected study segments provided a 3-year observed crash frequency to obtain a calibration factor for the HSM SPF and develop new SPFs. The calibration factor for the HSM SPF for rural two-lane two-way roads in Utah is 1.16. This indicates that the HSM underpredicts the number of crashes on rural two-lane two-way roads in Utah by sixteen percent.

Author: Srinivas Reddy Geedipally
Publisher:
ISBN:
Category : Traffic safety
Languages : en
Pages : 0

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The Highway Safety Manual (HSM) contains safety performance functions (SPFs) that are used in project-level decision-making for estimating the average crash frequency by severity level for existing conditions, alternatives to existing conditions, or proposed new roadways. However, SPF calibration is needed because most of the existing HSM SPFs were developed for states other than Texas. In addition, the HSM does not contain predictive models for frontage roads. Texas has a large network of frontage road segments that are part of the freeway system. Also, the ramp models in the HSM are not applicable to Texas due to differences in ramp configurations. Ramps in Texas usually connect the freeway mainline to the adjacent frontage road rather than a ramp terminal that connects directly to the perpendicular road, as is typical in the states used for developing the SPFs in the HSM. Researchers derived reliable local calibration factors to apply to Texas roadways for most of the SPFs in the HSM. For the facilities with poor calibration factors, researchers developed new SPFs. The calibration factors were developed by region for all facility types. Researchers developed new safety prediction models for one-way and two-way frontage roads and ramp segments. Researchers also developed an analysis spreadsheet tool to help practitioners implement the new models to facilitate analysis of all rural and urban roadway segments and intersections. In particular, the tool will assist in estimating the average crash frequency at a particular site and in evaluating different cross-sectional alternatives

Author: Imalka Chiranthi Matarage
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Crash prediction models in the Highway Safety Manual (HSM) are used to quantify the safety experience of existing and new roadways. Safety performance functions (SPFs) or crash prediction models are statistical formulas developed on limited data from a few selected states, Kansas not being one of those states. Therefore, the HSM recommends calibration of HSM-default SPFs, or development of local SPFs, to enhance accuracy of predicted crash frequency. This dissertation demonstrates the HSM calibration procedure and its' quality assessment for freeway segments, speed-change lanes, ramp segments, and crossroad ramp terminals in Kansas. The study used three years of recent crash data, the most recent geometric data, and HSM-recommended sample sizes for all facilities considered for the calibration. The HSM methodology overpredicted all fatal and injury (FI) crashes and underpredicted all property damage only (PDO) crashes for freeway segments. The HSM methodology consistently underpredicted both FI and PDO crashes for both entrance- and exit-related speed-change lanes. The HSM methodology overpredicted all FI crashes, underpredicted multiple vehicle PDO crashes, and overpredicted single vehicle PDO crashes for entrance ramp segments. In the case of exit ramp segments, the HSM methodology underpredicted all multiple vehicle crashes and overpredicted all single vehicle crashes. The HSM methodology overpredicted all FI crashes and underpredicted all PDO crashes for both signal- and stop-controlled crossroad ramp terminals. Cumulative residual plots and coefficient of variation were used to evaluate the quality of calibrated HSM-default SPFs. Results of calibration quality assessment indicated that estimated calibration factors were satisfactory for all freeway and ramp facilities considered in this study. However, for further accuracy and comparison purposes, calibration functions were developed to improve the fit to local data. Calibration functions were better fitted compared to calibrated HSM-default SPFs for freeway and ramp facilities in Kansas. Challenges faced, how those challenges were addressed, and data collection techniques used in this study are discussed. In summary, estimated calibration factors and developed calibration functions of this study would greatly improve making accurate decisions related to freeway and ramp safety in Kansas.

Author: Karen Dixon
Publisher: Transportation Research Board
ISBN: 0309213886
Category : Roads
Languages : en
Pages : 27

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Book Description
TRB’s National Cooperative Highway Research Program (NCHRP) Report 715: Highway Safety Manual Training Materials provides training materials to aid in implementing the American Association of State Highway and Transportation Officials’ Highway Safety Manual (HSM).

Author: Xiang Yu (Graduate of University of Missouri--Columbia)
Publisher:
ISBN:
Category :
Languages : en
Pages : 154

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According to several years' official crash data, a significant proportion of crashes happened at roadway intersections in Missouri. Of those intersection crashes, a large number of crashes occurred at urban roadway intersections. Although much safety research has been performed, it is still crucial to further understand the factors that contribute to crashes at such locations. It is also noticed that adverse weather and precipitation would lead to high crash risk and more severity crashes. Therefore, it is meaningful to do safety research about urban roadway intersections considering adverse weather and precipitation conditions. Safety Performance functions (SPFs) were built for urban two-lane four-leg unsignalized intersections and urban four-leg signalized intersections considering precipitation factors. All the intersection samples were collected from Missouri. For urban two-lane four-leg unsignalized intersections, AADT and precipitation factors were considered for developing SPF. For urban four-leg signalized intersections, AADT, speed limit, and precipitation factors were considered for building SPF. SPFs were built based on negative binomial regression model. Several diagnostics methods were used in model developing processes, such as Exploratory Data Analysis (EDA), Variable Introduction Exploratory Data Analysis (VIEDA), over-dispersion, log-likelihood, and cumulative residual plots (CURE Plot). The models revealed that precipitation factors have significant impacts on the safety of urban two-lane four-leg unsignalized intersections. However, for urban four-leg signalized intersections, the effects were not obvious. Calibration factors were also developed for several unsignalized intersections types in this thesis. Calibration factors can be applied to adjust crash frequency by comparing actual roadway conditions to base roadway conditions. The new calibration factors were almost same as HSM1.

Author: Lee August Rodegerdts
Publisher: Transportation Research Board
ISBN: 0309155118
Category : Technology & Engineering
Languages : en
Pages : 407

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Book Description
TRB's National Cooperative Highway Research Program (NCHRP) Report 672: Roundabouts: An Informational Guide - Second Edition explores the planning, design, construction, maintenance, and operation of roundabouts. The report also addresses issues that may be useful in helping to explain the trade-offs associated with roundabouts. This report updates the U.S. Federal Highway Administration's Roundabouts: An Informational Guide, based on experience gained in the United States since that guide was published in 2000.