Evaluating Driver Response to a Dynamic Speed Feedback Sign at a Freeway Exit Ramp Considering the Sign Design Characteristics and Lateral Installation Position

Research was conducted at a freeway exit ramp with significant horizontal curvature to evaluate the effectiveness of dynamic speed feedback signs (DSFS) as a speed reduction countermeasure. Several aspects of the DSFS were evaluated, including display size, border type, lateral installation position, and vehicle detection range. Three different full-matrix DSFS were utilized, which included: 15-inch display panel with yellow border, 18-inch display panel with yellow border, and 18-inch display panel with no border. Each sign was individually installed and tested at identical locations near the start of the exit ramp curve, in both the traditional right-side-mount and an alternative forward-mount within the exit gore area. Speed data and message activation location were collected for vehicles approaching and entering into the curve across the various sign test conditions. Overall, the presence of a DSFS positioned near the start of the curve resulted in curve entry speeds that were, on average, 3.5 mph lower than without a DSFS present at the site. The lowest curve entry speeds were observed for cases where the message activated when vehicles were within 250 to 400 ft of the curve. Interestingly, earlier message activation did not contribute to further speed reductions, although later activation substantially diminished the speed reduction effects. Regarding DSFS lateral position, both the side-mounted and forward-mounted DSFS installations resulted in similar curve entry speeds. Furthermore, there were no discernable differences in curve entry speeds between the 15-inch and 18-inch display panels, although the inclusion of a yellow sign border improved performance.

Biomechanics in Removable Partial Dentures: A Literature Review of FEA-Based Studies

The present study was aimed at reviewing the studies that used finite element analysis (FEA) to estimate the biomechanical stress arising in removable partial dentures (RPDs) and how to optimize it. A literature survey was conducted for the English full-text articles, which used only FEA to estimate the stress developed in RPDs from Jan 2000 to May 2021. In RPDs, the retaining and supporting structures are subjected to dynamic loads during insertion and removal of the prosthesis as well as during function. The majority of stresses in free-end saddle (FES) RPDs are concentrated in the shoulder of the clasp, the horizontal curvature of the gingival approaching clasp, and the part of the major connector next to terminal abutments. Clasps fabricated from flexible materials were beneficial to eliminate the stress in the abutment, while rigid materials were preferred for major connectors to eliminate the displacement of the prosthesis. In implant-assisted RPD, the implant receive the majority of the load, thereby reducing the stress on the abutment and reducing the displacement of the prosthesis. The amount of stress in the implant decreases with zero or minimal angulation, using long and wide implants, and when the implants are placed in the first molar area.

Driver Response to a Dynamic Speed Feedback Sign on Freeway Exit Ramps Based on Sign Location, Interchange Type, and Time of Day

A series of field evaluations was performed at three freeway interchange ramps in Michigan that possessed significant horizontal curvature to assess the impacts of a dynamic speed feedback sign (DSFS) on driver speed selection and brake response while approaching and entering the ramp curve. A DSFS with a 15 in. full-matrix display was temporarily installed at each of the three exit ramp locations. The sign was programmed to display the same feedback message at each location, which included the speed number for all approaching vehicles, which alternated with a “Slow Down” message for vehicles approaching above 40 mph. The effectiveness of the feedback sign was tested across various sign locations (at the point of curvature versus 350 ft upstream), interchange types (system versus service), time of day (peak versus off-peak), light conditions (daylight versus darkness), and vehicle types (passenger vehicles versus trucks). Compared with the pre-DSFS site condition, the DSFS reduced curve entry speeds and improved brake response at two of the three ramp locations. In general, the greatest beneficial effects on driver behavior were achieved when the DSFS was positioned at the point of curvature, during which curve entry speeds were reduced by approximately 2 mph. These findings were consistent between the system interchanges and service interchanges, and across all vehicle types. The DSFS was also found to be most effective during daytime off-peak periods compared with peak periods and at night. Further evaluation of DSFS at additional ramp locations, and considering an expanded set of conditions, is recommended.

Safety Effects of Horizontal Curve Design and Lane and Shoulder Width on Single Motorcycle Accidents in Norway

Factors related to the road infrastructure contribute to the occurrence of motorcycle accidents. This study investigates how design parameters of the existing rural two-lane road network in Norway influence the occurrence of single motorcycle accidents. The design elements considered in this study are horizontal curvature (curve type, degree of curvature, and adjacent curve requirements) and lane and shoulder widths. A matched case-control study design was applied to investigate the safety effects of these elements. Cases were defined as segments experiencing at least one single motorcycle accident during the study period from 2013 to 2017, while controls were defined as segments not experiencing an accident in the same period. In order to identify the segments, a GIS analysis was performed on data collected from the National Road Database (NVDB). In case-control studies, matching allows us to control for confounding variables. AADT and speed limit were used as matching variables in this study. A matching ratio of 4 : 1 (i.e., four controls per case) was used, resulting in 752 controls being matched to 188 cases. The results indicate horizontal alignment to have a more significant effect on single motorcycle accidents compared to lane and shoulder widths. Segments with several adjacent reverse curves, with high curvature (R < 200 m), have high odds for an accident. Further, if the requirements for adjacent curves are not fulfilled (i.e., considerable variation in adjacent curve radii), the odds increase even more. While the results are not statistically significant, trends seen indicate that wider lanes were associated with increased odds for an accident, while wider shoulders were associated with decreased odds. In comparison with a similar study considering passenger vehicles, the results of this study also indicate that horizontal alignment has a greater effect on single motorcycle accidents than on passenger vehicle accidents.

Analysis of the Effectiveness of Determining the Horizontal Curvature of a Track Axis Using a Moving Chord

The paper addresses the issue of determining the horizontal curvature of a railway track, noting that it is most often done indirectly – on the basis of measured sags from a chord stretched along the track. Further use of this method would not be justified if there were a direct method for determining the curvature. Therefore, the assumptions of the method for deter-mining the horizontal curvature from “Archives of Civil Engineering”, iss. 4/2020, are presented. This method is based on changes in the slope angles of the moving chord in the Cartesian coordinate system. Two important details are examined: the influence of the length of the chord on the obtained values of curvature and the possibility of determining the location of border points between particular geometrical elements. The analysed variants resulted from the type of transition curves used. It has been found that the length of the chord does not play a significant role in determining the curvature and does not limit the application of this method. At the same time, attention is drawn to the precision of determining the nature of the curvature and its compliance with the theoretical course on transition curves. The analysis shows that, in the moving chord method, it is possible to determine the location of the border points between the individual geometrical elements, but the required chord length must be adapted to the type of transition curve. Keywords: railway, horizontal curvature, moving chord, analysis methodology

ANALISIS PENGARUH KETEBALAN WEB TERHADAP KEAMANAN BOX GIRDER AKIBAT VARIASI SUDUT KELENGKUNGAN HORIZONTAL PADA JEMBATAN

In general, bridges are made in a straight shape, but with complex geometries, topographic factors, and efforts to prevent congestion, horizontal curved bridges are used at highways and toll roads. In building a bridge, good planning is needed especially in terms of strength. However, the use of improper dimensions will cause a bridge to be over-designed or under-designed. Therefore, the purpose of this research is to determine the effect of web thickness on the safety of prestressed concrete box girder due to variations in the horizontal curvature angle on the bridge. The span length of the analysed bridge is 60 m with a roller-joint placement and a single span bridge type. The angular variation of the horizontal curved bridge used are 0°, 15°, and 30°. The analysis was carried out using the Midas Civil 2020 program in accordance with the SNI 1725 : 2016 loading standard. The results of this analysis indicate that with increasing the thickness of prestressed concrete box girder web, it will cause increased stress and deflection on the bridge. Pada umumnya jembatan dibuat dengan bentuk lurus, namun dengan adanya geometri yang kompleks, faktor topografi, dan upaya untuk mencegah terjadinya kemacetan, jembatan lengkung horizontal digunakan pada simpang susun jalan raya dan jalan tol. Dalam membangun suatu jembatan, diperlukan perencanaan yang baik terutama dari segi kekuatan. Akan tetapi, dengan penggunaan dimensi yang tidak tepat akan menyebabkan suatu jembatan menjadi over-designed atau under-designed. Oleh karena itu, tujuan dari penelitian ini adalah untuk mengetahui pengaruh dari ketebalan web terhadap keamanan prestressed concrete box girder akibat variasi sudut kelengkungan horizontal pada jembatan. Panjang bentang jembatan yang dianalisis adalah 60 m dengan perletakan sendi-rol dan jenis jembatan single span. Variasi sudut jembatan lengkung horizontal yang digunakan adalah 0°, 15°, dan 30°. Analisis dilakukan dengan menggunakan program Midas Civil 2020 sesuai dengan standar pembebanan SNI 1725 : 2016. Hasil dari analisis ini menunjukkan bahwa dengan meningkatnya ketebalan web prestressed concrete box girder, akan menyebabkan meningkatnya tegangan dan juga defleksi pada jembatan.

Identifying Roadway Physical Characteristics That Contribute to Emissions Differences between Hybrid and Conventional Vehicles

Conventional vehicles and hybrid electric vehicles (HEVs) will be the dominant vehicle types in the U.S. private passenger vehicle fleet for the foreseeable future. This study used a real-time data set obtained from monitoring vehicle performance and emissions from a series of test runs from a conventional vehicle and a HEV over an 18-month period. An innovative new method of analysis allowed the assessment of different emissions rates between the two propulsion systems and the attribution of these differences to physical roadway/infrastructure characteristics. Regression and cross-classification results identify specific roadway characteristics that contribute to emissions differences between the vehicle types. Overall, the models that included maximum grade and intersection control type performed best, however, speed limit and horizontal curvature were also shown to be important. The performance differences identified in this project confirm that engine controls that are responsive to roadway characteristics are necessary.

Evaluación de la estabilidad de taludes en cárcavas, Huasca de Ocampo, Hidalgo, México.

In Santo Domingo, Huasca de Ocampo, Hidalgo, changes in the use of soil, the topographic and geomorphological conditions and the increase of runoffs, promote the formation of gullies in agricultural areas, causing the loss of soil fertility and a reduction of agricultural land. The objective of our research was to identify the main topographic features and physical/mechanical properties of the soil that cause a sidewall retreat of gullies (AV); determination was performed through principal component analysis (PCA) and multiple linear regression (MLR). The AV varied from 0.04 to 0.17 m yr‑1 with a mean value of 0.092 m yr-1. The most important variables in the PCA were: height, slope, orientation, vertical and horizontal curvature, transversal slope, ridge thickness, bulk density (0 to 5 and 5 to 10 cm), penetration resistance (2.5, 5 and 10 cm), hydraulic conductivity, shrinkage index, plasticity index, 0.25, 0.15 and 0.075 mm particles, cohesion and soil erodibility factor. The best linear regression explanatory model presented a f it value of 84.02% using four variables (particles of 0.15 and 0.075 mm, slope and ridge thickness). The AV is influenced by the presence of silt and clay in the regolith and soil surface (ridge), which are vulnerable to wetting and drying processes that boost the formation of cracks and disaggregation of the components of ridge and slope, reducing the soil’s resistance to erosion and causing headward erosion and instability in the gully slopes.