Daniel J. Findley

Modeling the impact of spatial relationships on horizontal curve safety

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 drivers expectation to encounter additional curves. The link between an individual curves 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.

Curve Collisions: Road and Collision Characteristics and Countermeasures

Horizontal curves are relatively dangerous portions of roadway networks. Agencies optimizing the use of safety funds should be aware of characteristics of the collisions on those segments. However, few previously published articles attempted to characterize collisions on horizontal curves. This article describes an effort that characterized collisions reported to be on curves in North Carolina using the Highway Safety Information System. More than 51,000 North Carolina (NC) collisions on two-lane road curves were compared to collisions on all two-lane roads and on all roads. In doing so we gained a perspective of how well various curves perform relative to other road areas. We investigated numerous two-lane curve-collision types. Those most overrepresented included: collisions on grades, rural, severe injury or fatal, fixed object (particularly tree, ditch, and embankment), overturn, off-peak hours (particularly during darkness on unlighted roads), weekend, holiday periods, and wet, icy, or snowy pavement. The analysis also revealed that there were few short roadway segments (of 0.1- to 1-mile length) with more than 10 reported curve collisions in 3 years. This article provides recommendations from the literature to treat overrepresented collision types on horizontal curves. Based on the analysis findings, agencies should target countermeasures for the most common and overrepresented collision types.

Evaluation of GIS applications for horizontal curve data collection

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 ...

Collecting Horizontal Curve Data: Mobile Asset Vehicles and Other Techniques

Mobile asset data collection vehicles can provide transportation agencies with inventories of various roadway and roadside elements containing location information, element type, and condition data. Horizontal curves are of interest to agencies because they have been shown to be hazardous roadway components and have potential for mobile data collection concurrently with other roadway elements. The cost of manually acquiring horizontal curvature data to develop an inventory can be prohibitive for many agencies, so understanding the applicability of a mobile asset data collection effort for curves is important. The objective of this work was to study the ability of multiple commercial roadway inventory vehicles and to compare them to other methods for determining the geometric characteristics of horizontal curves. The comparison is based on data from three commercial vendors of roadway asset inventory data on a 38.8-km (24.1-mi) course in central North Carolina. Among the 16 curves studied, at least one vendor was within 10% of the radius value found with the manual chord method for six of the curves and within 25% for 13 of the curves. Only three curves had a larger radius variant. For the length measurements of the 16 curves, at least one vendor was within 10% of the length from the chord method for eleven of the curves and within 25% for fifteen of the curves. Only one curve had a larger length variant. The mobile vehicle vendors provided more accurate and consistent curve length measurements than radius measurements. Agencies that consider using mobile data collection vehicles for horizontal alignments should understand the limitations of each horizontal curve estimating technique and the changes that can occur in the radius within the curve. Collaborating with vendors to define the changes in roadway alignment that constitute a curve, the associated beginning and ending of the curve, and geometric characteristics can provide agencies the most appropriate data to meet their needs.

Considerations for Effective Lidar Deployment by Transportation Agencies

Lidar is becoming increasingly popular across the United States, and state transportation agencies are adopting this technology for practical uses in transportation-related applications. This trend can be seen in the growing number of agencies acquiring lidar scanners and contracting lidar services. The primary factors behind this trend are that (a) surveyors, engineers, and technicians are becoming more educated about and increasingly open to lidar and its applications and (b) lidar is potentially more cost-effective than traditional surveying technologies. Lidar can provide transportation agencies with the benefits of safety, data collection productivity, cost-effectiveness, applicability, high levels of detail, and technological advancement. Many of the more practical uses and benefits of lidar have come to fruition in recent years, and transportation agencies have been more open to its use. However, little more than anecdotal evidence supports when a specific lidar platform should be applied for various applications rather than a traditional surveying method. Decision makers in geomatic and surveying departments that use lidar must regularly weigh the options of which surveying method to use for specific projects and base decisions on performance tradeoffs. The methodology presented in this paper aims to provide guidance on how agencies may determine whether lidar can be practically used within their organizations. The aspects and performance measures outlined for effective deployment of lidar equipment or contracted services should be systematically considered.

Retaining Wall Field Condition Inspection, Rating Analysis, and Condition Assessment

In the past, highway retaining walls were assets that were often excluded from inventory programs and were regarded as noncritical or lost assets. With the recognition that wall failures may be detrimental to the roadway and the surroundings and may pose potential hazards to the safety of the public, several highway agencies have begun to incorporate retaining walls into their inventory and inspection programs. Work in this paper addresses the development of a system for the inventory and condition assessment of retaining walls serving various functions within the highway infrastructure. Critical elements of data collection are identified and a retaining wall information collection and assessment system (WICAS) is proposed. WICAS is designed such that data can be readily collected in the field. A condition assessment model is also proposed and is used to define a retaining wall rating metric. The rating system is designed so that those elements of a wall that are deemed to be in critical distress conditions are readily identified and not overlooked through the presentation of an overall average rating for the entire wall.

Evaluation of radar vehicle detection at four quadrant gate rail crossings

As train frequencies and traffic volumes increase, the need for safer at grade highway/rail crossings is paramount. Closing or grade separating crossings ultimately cannot work for all situations; therefore four quadrant gates may be used to provide a higher level of safety than conventional crossing treatments. At crossings between two adjacent signalized intersections, signal preemption may prevent vehicles from queuing within the crossing island, but some risk of vehicles becoming trapped by the timed exit gate descents still remains. Sensors can be installed to detect vehicles and would extend exit gate closure until the crossing island is clear or conversely allow for either simultaneous or near simultaneous entry and exit gate descents, if no vehicles are present. Radar detection was installed at three sites on North Carolina Railroad Companys H-Line in January 2014. Each crossing activation was broken down into 8 stages based on operating conditions of the gate system. The average duration of the time period when all gates are fully deployed increased considerably during the after period (when radar modified the exit gate behavior) by 10–17 s, providing a longer duration of a sealed crossing before the train arrived.

North Carolina Ferry System: A Study

The North Carolina Department of Transportation Ferry Division faces several challenges. Recent U.S. Coast Guard (USCG) regulations increasing the minimum crew size on vessels carrying more than 149 passengers require the North Carolina Ferry System (NCFS) to add 79 employees. Difficulty in finding additional funds and certified crew to meet these regulations, coupled with reduced NCFS financial allocations from recent state budget cuts, resulted in a reduced number of ferry sailings on some routes during the peak operation period in the summer of 2009. In addition, NCFS experienced challenges from ferry service outages that resulted from the need to operate aging ferry vessels, a lack of standby ferry vessels in case of breakdowns, and vessels out of service as a result of the increased frequency of USCG dry dock inspections. The NCFS must also contend with unreliable support vessels that have exceeded their useful lives and a lack of certified welders and marine electricians to support maintenance functions. However, these resource and operation challenges present an opportunity to analyze existing ferry operations and to explore future opportunities.

Estimating the Effect of Standard Enforcement of a Rear Seat Belt Law for Rear Seat Fatality Prevention

Data were collected from the NHTSA’s Fatality Analysis Reporting System to analyze the link between primary enforcement of rear seat belt use and injury severity in fatal vehicle collisions. Specifically, this study predicted the amount of fatalities that may have been prevented had there been standard enforcement of a rear seat belt law in effect. Previous literature concludes that increasing seat belt use will decrease injury severity in collisions and the primary enforcement of seat belts laws will increase seat belt use by approximately 14%. This study recorded and compared the number of rear seat fatalities in states that did and did not have primary enforcement laws for rear seat occupants. The results indicated that, on average, for every properly restrained rear seat fatality there are 0.45 more rear seat fatalities in states without primary enforcement than states with primary enforcement. It also predicts that the states that do not practice standard seat belt enforcement could have seen approximately 772 to 1,032 fatalities prevented from 2011 to 2015, had there been primary rear seat belt enforcement. This corresponds to an estimated national crash cost savings of

Comparison of Three Retaining Wall Condition Assessment Rating Systems

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