Safety Evaluation of Horizontal Curves on Rural Undivided Roads

Khan, Ghazan; Bill, Andrea R.; Chitturi, Madhav; Noyce, David A.

doi:10.3141/2386-17

Cited by 38 publications

(20 citation statements)

References 10 publications

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“…Fink and Krammes [7] and Persaud et al [8] used a higher number of data, more than 500. In contrast, Zegeer et al [9], Sakshaug [10] and Khan et al [11] had more than 10,000 curves. They obtained the information about road geometry from national road databases.…”

Section: Introductionmentioning

confidence: 99%

ROCA – An ArcGIS toolbox for road alignment identification and horizontal curve radii computation

et al. 2018

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We present the ROCA (ROad Curvature Analyst) software, in the form of an ESRI ArcGIS Toolbox, intended for vector line data processing. The software segments road network data into tangents and horizontal curves. Horizontal curve radii and azimuth of tangents are then automatically computed. Simultaneously, additional frequently used road section characteristics are calculated, such as the sinuosity of a road section (detour ratio), the number of turns along an individual road section and the average cumulative angle for a road section. The identification of curves is based on the naïve Bayes classifier and users are allowed to prepare their own training data files. We applied ROCA software to secondary roads within the Czech road network (9,980 km). The data processing took less than ten minutes. Approximately 43% of the road network in question consists of 42,752 horizontal curves. The ROCA software outperforms other existing automatic methods by 26% with respect to the percentage of correctly identified curves. The segmented secondary roads within the Czech road network can be viewed on the roca.cdvgis.cz/czechia web-map application. We combined data on road geometry with road crashes database to develop the crash modification factors for horizontal curves with various radii. We determined that horizontal curves with radii of 50 m are approximately 3.7 times more hazardous than horizontal curves with radii accounting for 1000 m. ROCA software can be freely downloaded for noncommercial use from https://roca.cdvinfo.cz/ website.

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Section: Introductionmentioning

confidence: 99%

ROCA – An ArcGIS toolbox for road alignment identification and horizontal curve radii computation

et al. 2018

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“…There has been considerable research conducted in recent years into establishing relationships between crashes and various traffic flow characteristics for freeway segments. Most of the research has focused on determining the relationship between crashes and highway traffic volumes, while little attention has been focused on the relationships of vehicle density, level of service (LOS), volume/ capacity (v/c) ratio, and speed distribution (4)(5)(6)(7). Most researchers only focused on selected segments of a particular facility and did not consider the roadway system as a whole while exploring the relationship between crash rates and flow parameters (8)(9)(10).…”

Section: Literature Reviewmentioning

confidence: 99%

Assessment of the Effects of Volume Completeness and Spatial and Temporal Correlation on Hourly Freeway Crash Prediction Models

Dutta¹,

Fontaine

2020

Transportation Research Record

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Traditional traffic safety analyses of crash frequency usually use highly aggregated cross-sectional data and ignore the time-varying nature of some critical factors. This research used 7 years of hourly data from 110 rural four-lane segments and 80 urban six-lane segments to develop hourly level crash prediction models and contrasted them with traditional annual average daily traffic (AADT)-based models. To account for the overdispersion of data and unobserved heterogeneity, generalized linear mixed-effect models were contrasted with negative binomial models. The models used average hourly volume as a measure of exposure, and the quantity of volume data available for the sites ranged from continuous counts to locations where only a couple of weeks of data were available every other year (short counts). While developing disaggregated models, the difference in data availability from these sources can be a potential source of error, so evaluating the change in performance of prediction models with changes in volume data availability was examined. The results showed that the best models include a combination of average hourly volume, selected geometric variables, and speed related parameters. Hourly models that included speed parameters consistently outperformed AADT models. Further investigation revealed that the positive effect of using a more inclusive and larger dataset was larger than the effect of accounting for data correlation. This showed that using short count stations as a data source does not diminish the quality of the developed models, thus indicating that these methods could be applied broadly across agencies, even when volume data is relatively sparse.

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“…The studies include those of Fitzpatrick et al (2010), Bauer and Harwood (2013), Khan et al (2013), Banihashemi (2015Banihashemi ( , 2016 and Gooch et al (2016). Although all the studies included in Figure 1 show that the number of accidents (traffic volume is controlled for in all studies) increases as curve radius declines, there are many important differences between the studies.…”

Section: Figure 1 About Herementioning

confidence: 99%

Can evolutionary theory explain the slow development of knowledge about the level of safety built into roads?

Elvik

2017

Accident Analysis & Prevention

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In several papers, Hauer (1988, 1989, 2000a, 2000b, 2016) has argued that the level of safety built into roads is unpremeditated, i.e. not the result of decisions based on knowledge of the safety impacts of design standards. Hauer has pointed out that the development of knowledge about the level of safety built into roads has been slow and remains incomplete even today. Based on these observations, this paper asks whether evolutionary theory can contribute to explaining the slow development of knowledge. A key proposition of evolutionary theory is that knowledge is discovered through a process of learning-by-doing; it is not necessarily produced intentionally by means of research or development. An unintentional discovery of knowledge is treacherous as far as road safety is concerned, since an apparently effective safety treatment may simply be the result of regression-to-the-mean. The importance of regression-to-the-mean was not fully understood until about 1980, and a substantial part of what was regarded as known at that time may have been based on studies not controlling for regression-to-the-mean. An attempt to provide an axiomatic foundation for designing a safe road system was made by Gunnarsson and Lindström (1970). This had the ambition of providing universal guidelines that would facilitate a preventive approach, rather than the reactive approach based on accident history (i.e. designing a system known to be safe, rather than reacting to events in a system of unknown safety). Three facts are notable about these principles. First, they are stated in very general terms and do not address many of the details of road design or traffic control. Second, they are not based on experience showing their effectiveness. Third, they are partial and do not address the interaction between elements of the road traffic system, in particular road user adaptation to system design. Another notable fact consistent with evolutionary theory, is that the safety margins built into various design elements have been continuously eroded by the development of bigger and faster motor vehicles, that can only be operated safely if roads are wider and straighter than they needed to be when motor vehicles were smaller and moved slower.

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Safety Evaluation of Horizontal Curves on Rural Undivided Roads

Cited by 38 publications

References 10 publications

ROCA – An ArcGIS toolbox for road alignment identification and horizontal curve radii computation

ROCA – An ArcGIS toolbox for road alignment identification and horizontal curve radii computation

Assessment of the Effects of Volume Completeness and Spatial and Temporal Correlation on Hourly Freeway Crash Prediction Models

Can evolutionary theory explain the slow development of knowledge about the level of safety built into roads?

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