Case–control and cross-sectional methods for estimating crash modification factors: Comparisons from roadway lighting and lane and shoulder width safety effect studies

Groß, Frank; Donnell, Eric T.

doi:10.1016/j.jsr.2011.03.003

Cited by 59 publications

(28 citation statements)

References 12 publications

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“…These methods showed that crash frequency was reduced with increasing shoulder width. Gross and Donnell [19] used two methods to determine crash modification factors (CMFs). Their study utilized case-control and cross-sectional analyses to calculate CMFs for fixed roadway lighting and allocation of lane and shoulder widths.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Road Shoulder and Weather Conditions on the Occurrence of Rollover Crashes in Two-lane Highways

Kordani¹,

Shirini²,

Yazdani³

2019

Period. Polytech. Civil Eng.

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Rollover crash is a type of dangerous crash that occurs often in two-lane highways. Therefore, this study evaluates the effect of road shoulder and weather condition on rollover crashes. Crash data show that 8,609 crashes were recorded from 2006 to 2009 on six two-lane highways located at the center of Iran. This data contains 1860 rollover crashes. Rollover crash in this paper not included the head on crashes and fixed object crashes. Therefore the rollover crashes are only single vehicle crashes. Binary logit was selected for modelling since there were two possible outcomes: rollover crashes and other crash types. The variables of the final model include highway class, road shoulder width, as well as rainy, snowy, foggy and night conditions. The modeling results show that rainy and foggy variables, with coefficients of 0.731 and 0.719 respectively, had the greatest effects on rollover crash occurrence. Also, road shoulder width and night conditions, with coefficients of 0.221 and 0.184 respectively, had the least effects on rollover crash occurrence. Afterward, sensitivity analysis was performed on all the independent variables, and the results show variable variation and indicate that the probability of rollover crash occurrence is 21.29 % on the mentioned highway.

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Section: Introductionmentioning

confidence: 99%

The Effect of Road Shoulder and Weather Conditions on the Occurrence of Rollover Crashes in Two-lane Highways

Kordani¹,

Shirini²,

Yazdani³

2019

Period. Polytech. Civil Eng.

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“…Literature shows that the obtained values are reasonable for such models[25] [29]. However, all crashes and all lane-departure crashes may overestimate the safety effectiveness of the treatments.…”

mentioning

confidence: 86%

“…Equation 1 shows the general form of the negative binomial regression model which is modified for the crash frequency modeling [24] [25].…”

Section: Model Developmentmentioning

confidence: 99%

An Alternative Regression-Based Approach to Estimate the Crash Modification Factors of Multiple Treatments Using Before-and-After Data

Galgamuwa¹,

Dissanayake²

2018

JTTs

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Before-and-after methods have been effectively used in the road safety studies to estimate Crash Modification Factors (CMFs) of individual treatments as well as the multiple treatments on roadways. Since the common practice is to apply multiple treatments on road segments, it is important to have a method to estimate CMFs of individual treatment so that the effect of each treatment towards improving the road safety can be identified. Even though there are methods introduced by researchers to combine multiple CMFs or to isolate the safety effectiveness of individual treatment from CMFs developed for multiple treatments, those methods have to be tested before using them. This study considered two multiple treatments namely 1) Safety edge with lane widening 2) Adding 2 ft paved shoulders with shoulder rumble strips and/or asphalt resurfacing. The objectives of this research are to propose a regression-based method to estimate individual CMFs estimate CMFs using before-and-after Empirical Bayes method and compare the results. The results showed that having large sample size gives accurate predictions with smaller standard error and p-values of the considered treatments. Also, results obtained from regression method are similar to the EB method even though the values are not exactly the same. Finally, it was seen that the safety edge treatment reduces crashes by 15%-25% and adding 2 ft shoulders with rumble strips reduces crashes by 25%-49%.

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“…Researchers applied this method to calculate CMFs for the effects of lane width, shoulder width, and presence of edge-line marking for frontage roads, and median width for freeways and rural multilane highways [22]. However, the cross-sectional method sometimes overestimates the effect of the countermeasure due to the presence of confounding variables, whereas case-control method estimates the casual-effects while controlling impacts of confounding variables [23]. Although this method can be used to investigate the effect of multiple countermeasures, the data collection and sample selection become very complex in case of multiple countermeasures [24].…”

Section: Literature Reviewmentioning

confidence: 99%

Simulation-Based Framework for Estimating Crash Modification Factors (CMFs): A Case Study for ITS Countermeasures

Das

Park

Bhavsar³

2019

Journal of Advanced Transportation

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The efficient movement of users and goods is the primary purpose of the surface transportation system. Roadway traffic crashes have devastating impacts on quality of life of the users as well as health of the system. While researchers are utilizing advanced computing and communication tools to reduce number of crashes on the roadways, there is still an absence of appropriate method to evaluate the safety performances of these advanced technologies in the planning stage. Development of crash modification factors (CMFs) is a standard method to evaluate the safety effect of proposed countermeasures. Though, the current practices of developing CMFs are not efficient and cost-effective in case of addressing impacts of Intelligent Transportation System (ITS) countermeasures. This study demonstrated a proof of concept of simulation-based framework for determining CMFs for ITS countermeasures. The proposed framework includes the application of traffic microsimulation model and Surrogate Safety Assessment Model (SSAM) developed by Federal Highway Administration (FHWA). The integration of these two models is suggested to estimate CMFs efficiently. However, the calibration of traffic microsimulation model and SSAM model is essential to portrait the real-world scenarios. A case study for estimating CMFs of ITS countermeasures was conducted to validate the proposed simulation-based approach. Four ITS countermeasures were considered: ramp metering, variable speed limit, junction control, and dynamic lane assignment. They were coded in traffic microsimulation environment and vehicle trajectory files were generated to import into SSAM model. After analyzing these trajectory files in SSAM tool, it was found that all proposed ITS countermeasures, except variable speed limit assignment, could reduce the number of crashes at crash prone locations.

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Case–control and cross-sectional methods for estimating crash modification factors: Comparisons from roadway lighting and lane and shoulder width safety effect studies

Cited by 59 publications

References 12 publications

The Effect of Road Shoulder and Weather Conditions on the Occurrence of Rollover Crashes in Two-lane Highways

The Effect of Road Shoulder and Weather Conditions on the Occurrence of Rollover Crashes in Two-lane Highways

An Alternative Regression-Based Approach to Estimate the Crash Modification Factors of Multiple Treatments Using Before-and-After Data

Simulation-Based Framework for Estimating Crash Modification Factors (CMFs): A Case Study for ITS Countermeasures

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