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Rasdorf W.,North Carolina State University | Findley D.J.,North Carolina State University | Zegeer C.V.,Engineering and Planning Highway Safety Research Center | Sundstrom C.A.,Highway Safety Research Center | Hummer J.E.,North Carolina State University
Journal of Computing in Civil Engineering

Applications that use a geographic information system (GIS) are common and useful in the field of transportation. Horizontal curves are critical components on a roadway in their role as a transition between straight segments and in their potential as a safety hazard to motorists. Therefore, determining the characteristics of curves [both spatial (including location, length, radius) and nonspatial (including traffic volume, signage, pavement type)] is an important task. GIS applications have been developed for evaluating roadway alignments in general and some have focused on horizontal curve assessment. This paper reports on two benchmarking efforts. The first assessed and established the accuracy of three publicly available GIS applications for determining curve spatial characteristics. The second assessed the quality of available GIS roadway line work. The three GIS applications were evaluated for performance accuracy on the basis of a comparison with precisely drawn curves [with radii ranging from 30.5 to 1,524m (100 to 5,000ft)]. The line work was evaluated on the basis of a comparison with field measurements from 51 curves [with radii ranging from 61.6 to 1,832.2m (202 to 6,011ft)]. The analysis found that the use of a GIS to accurately determine horizontal curve radius and length is possible. The Curvature Extension GIS application is recommended for individual curve analysis while Curve Calculator can produce sufficient results for individual curves if a substantial number of GIS points exist (8 points for an error of approximately 1% and 25 GIS points for an error of less than 0.1%). For network or route analysis, Curve Finder is recommended. This paper presents the methodology and analysis that led to these findings. © 2012 American Society of Civil Engineers. Source

Sandt L.S.,Highway Safety Research Center | Marshall S.W.,University of North Carolina | Rodriguez D.A.,University of California at Berkeley | Evenson K.R.,University of North Carolina | And 2 more authors.
Accident Analysis and Prevention

Background Few studies have comprehensively evaluated the effectiveness of multi-faceted interventions intended to improve pedestrian safety. "Watch for Me NC" is a multi-faceted, community-based pedestrian safety program that includes widespread media and public engagement in combination with enhanced law enforcement activities (i.e.; police outreach and targeted pedestrian safety operations conducted at marked crosswalks) and low-cost engineering improvements at selected crossings. The purpose of this study was to estimate the effect of the law enforcement and engineering improvement components of the program on motor vehicle driver behavior, specifically in terms of increased driver yielding to pedestrians in marked crosswalks. Methods The study used a pre-post design with a control group, comparing crossing locations receiving enforcement and low-cost engineering treatments (enhanced locations) with locations that did not (standard locations) to examine changes in driver yielding over a 6-month period from 2013 to 2014. A total of 24,941 drivers were observed in 11,817 attempted crossing events at 16 crosswalks in five municipalities that were participating in the program. Observations of real pedestrians attempting to use the crosswalks ("naturalistic" crossing) were supplemented by observations of trained research staff attempting the same crossings following an established protocol ("staged" crossings). Generalized estimating equations (GEE) were used to model driver yielding rates, accounting for repeated observations at the crossing locations and controlling other factors that affect driver behavior in yielding to pedestrians in marked crosswalks. Results At crossings that did not receive enhancements (targeted police operations or low-cost engineering improvements), driver yielding rates did not change from before to after the Watch for Me NC program. However, yielding rates improved significantly (between 4 and 7 percentage points on average) at the enhanced locations. This was true for both naturalistic and staged crossings. Conclusions This study provides evidence that enhanced enforcement and low-cost engineering improvements, as a part of a broader program involving community-based outreach, can increase driver yielding to pedestrians in marked crosswalks. These data are important for the staff and decision-makers involved in pedestrian safety programs to gain a better understanding of the different engineering and behavioral mechanisms that could be used to improve driver yielding rates. Source

Findley D.J.,North Carolina State University | Hummer J.E.,North Carolina State University | Rasdorf W.,North Carolina State University | Zegeer C.V.,Highway Safety Research Center | Fowler T.J.,North Carolina State University
Accident Analysis and Prevention

The curved segments of roadways are more hazardous because of the additional centripetalforces exerted on a vehicle, driver expectations, and other factors. The safety of a curve is dependent on various factors, most notably by geometric factors, but the location of a curve in relation to other curves is also thought to influence the safety of those curves because of a driver's expectation to encounter additional curves. The link between an individual curve's geometric characteristics and its safety performance has been established, but spatial considerations are typically not included in a safety analysis. The spatial considerations included in this research consisted of four components: distance to adjacent curves, direction of turn of the adjacent curves, and radius and length of the adjacent curves. The primary objective of this paper is to quantify the spatial relationship between adjacent horizontal curves and horizontal curve safety using a crash modification factor. Doing so enables a safety professional to more accurately estimate safety to allocate funding to reduce or prevent future collisions and more efficiently design new roadway sections to minimize crash risk where there will be a series of curves along a route. The most important finding from this research is the statistical significance of spatial considerations for the prediction of horizontal curve safety. The distances to adjacent curves were found to be a reliable predictor of observed collisions. This research recommends a model which utilizes spatial considerations for horizontal curve safety prediction in addition to current Highway Safety Manual prediction capabilities using individual curve geometric features. © 2011 Elsevier Ltd. All rights reserved. Source

Torbic D.J.,Midwest Research Institute | Harwood D.W.,Midwest Research Institute | Bokenkroger C.D.,Midwest Research Institute | Srinivasan R.,Highway Safety Research Center | And 3 more authors.
Transportation Research Record

A coordinated effort is under way to develop a Highway Safety Manual (HSM) for use in making quantitative estimates of the safety performance of specific highway types and quantitative estimates of proposed improvements to specific highway types. The highway types being addressed in the first edition of HSM are rural two-lane highways, rural multilane highways, and urban and suburban arterials. Explicit consideration of pedestrian safety on urban and suburban arterials is considered critical to implementation of the first edition of HSM. The objective of the present research was to develop a methodology for quantifying the effects of existing site characteristics and proposed improvements on urban and suburban arterials on pedestrian safety. The pedestrian safety prediction methodology has been developed to function as a component of the overall safety prediction methodology for urban and suburban arterials proposed for the first edition of HSM. In the present research, a methodology for prediction of vehicle-pedestrian collisions at signalized intersections was developed. This methodology includes base models for three- and four-leg signalized intersections and several accident modification factors. Source

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