Vertical Curve Research Articles

PHYSIC-CHEMICAL PROPERTIES OF TYPICAL CHERNOZEMS OF PRYDNISTERSK PODILLYA

This article analyzes the physic-chemical properties of typical chernozems. According to the methods, a laboratory study was performed. Physic-chemical parameters that are typodiagnostic for subfacial classification division of typical chernozems of the Prydnistersk Podillya are determined. Typical chernozems of the Prydnistersk Podillya are low-humus (2.78–3.98%). With depth, the humus content decreases by an average of 0.2% for every 10 cm, which indicates a uniformly accumulative type of distribution of organic matter in the profile of chernozems. In the same direction, humus reserves are declining. There is a spatial correlation between the humus content and the amount of physical clay in the fine soil.
 Humic acids predominate in the humus to a depth of 90–100 cm (Sgk: Sfk is 1.12–1.78). The general tendency of relative “fulvatization” of the arable layer as a result of its agrotechnical depletion is noticed. In relation to SGC to total organic C, chernozems of the study area are characterized by a high and very high degree of humification of organic matter. It is highest (62–70%) in the soils of the key section “Humentsi”, decreasing to 52–62% and 43–63% in the western direction.
 The humic acids of typical chernozems are dominated by calcium humates (GK-2). The largest number of them (29–35%) is concentrated on the contact boundary of humus and carbonate profiles. The convex nature of the distribution curves of the fraction of 2 humic acids and a sharp decrease in its content deeper than 100 cm, indicates their high migration capacity and the possibility of significant deposition of only a significant excess of calcium carbonates. The intensity of migration processes of the GK-2 fraction decreases in the direction of increasing the stiffness of hydrothermal conditions, due to the pulling of carboxylic acid salts closer to the soil surface, supersaturation of the solution with calcium bicarbonate, and as a consequence, increasing the total alkalinity in the humus horizon.
 The capacity of cation exchange (ECO) of typical chernozems is quite high (29–32 mmol-eq / 100 g of soil) with the dominance of calcium and magnesium cations in the composition of the soil-absorbing complex (GVC). There is a general tendency to increase these indicators in chernozems with low values ​​of SCC of the territory.
 The pH of the aqueous extract of typical chernozems of the Prydnistersk Podillya increases with depth from weakly acidic in the arable horizon to weakly and medium-alkaline within the carbonate profile. The reasons for such changes in the increase with the depth of the concentration of Ca2 + bicarbonates, which in their dissociation leads to an increase in the amount of hydroxyl ion and increase the alkalinity of the soil.
 The carbonate profile of typical chernozems is dominated by migratory forms of carbonate neoplasms - mold, carbonate plaque, veins. The vertical curve of carbonate content has an eluvial-illuvial type of profile structure. The content and reserves of carbonates in the 1.5-meter layer of typical chernozems increase from the west (434–714 t / ha) to the east (979–1847 t / ha).
 Key words: physic-chemical properties, typical chernozems, humic horizon, humic acids, carbonate profile.

Assessing the reliability of wind power operations under a changing climate with a non-Gaussian bias correction

Facing increasing societal and economic pressure, many countries have established strategies to develop renewable energy portfolios whose penetration in the market can alleviate the dependence on fossil fuels. In the case of wind, there is a fundamental question related to the resilience and hence profitability of future wind farms to a changing climate, given that current wind turbines have lifespans of up to 30 years. In this work we develop a new non-Gaussian method to adjust assimilated observational data to simulations and to estimate future wind, predicated on a trans-Gaussian transformation and a clusterwise minimization of the Kullback–Leibler divergence. Future winds abundance will be determined for Saudi Arabia, a country with a recently established plan to develop a portfolio of up to 16 GW of wind energy. Further, we estimate the change in profits over future decades using additional high-resolution simulations, an improved method for vertical wind extrapolation and power curves from a collection of popular wind turbines. We find an overall increase in daily profit of $272,000 for the wind energy market for the optimal locations for wind farming in the country.

The Influence Of Traffic Control Devices And Road Geometric Characteristics On Traffic Crushes Of Rular Two Lane Road

Traffic accidents worldwide are among the most alarming phenomena because they cost billions of dollars due to death rates and property damage. In Ethiopia, the accident fatality rate is becoming one of the most serious problems. Specifically, in rural highways where in there are problems with traffic control device enforcement and geometric deficiencies. Gedeo zone faces a similar problem that is considered a hot issue on-road crash. This study focused on the influence of traffic control devices and geometric characteristic related to road crashes. The data collection method was a purposive sampling technique considering both primary and secondary data collection system. Direct field observations were conducted, such as field survey and recording of the existing road geometric elements to figure out which geometric element contributory to traffic crashes. The data collected from the police traffic was categorized by clustering the road into different road segments composed of the same geometric characteristics. The severity of the accident analyzed and identified the hazardous road sections (black spot area). The relationships of accident crash established between the influence of traffic control access devices and geometric elements on the crash reduction at the identified accident-prone areas. Further, the study used ANN modeling through engineering software MATLAB to analyze the weight age of crashes on specified road segments concerning geometric road characteristics. Hence, the gradient carriageway width, super-elevation, cross slope, gradient, sight distance number of the horizontal curve, number of vertical curves, and AADT are the major factors for the occurrence of both fatal and injury at the blackspot segment along the rural highway.

Estimating the Ultimate Bearing Capacity for Strip Footing Near and within Slopes Using AI (GP, ANN, and EPR) Techniques

Numerical and computational analyses surrounding the behavior of the bearing capacity of soils near or adjacent to slopes have been of great importance in earthwork constructions around the globe due to its unique nature. This phenomenon is encountered on pavement vertical curves, drainages, and vertical infrastructure foundations. In this work, multiple data were collected on the soil and footing interface parameters, which included width of footing, depth of foundation, distance of slope from the footing edge, soil bulk density, slope and frictional angles, and bearing capacity factors of cohesion and overburden pressure determined for the case of a foundation on or adjacent to a slope. The genetic programming (GP), evolutionary polynomial regression (EPR), and artificial neural network (ANN) intelligent techniques were employed to predict the ultimate bearing capacity of footing on or adjacent to a slope. The performance of the models was evaluated as well as compared their accuracy and robustness with the findings of Prandtl. The results were observed to show the superiority of GP, EPR, and ANN techniques over the computational works of Prandtl. In addition, the ANN outclassed the other artificial intelligence methods in the exercise.

SPOT SPEED LIMIT STUDIES OF AGAIE-KATCHA-BARO ROAD AGAIE, NIGER STATE

The number of accidents in Nigeria increases relatively from year to year, despite the fact that there are many programs organized by the authority to reduce them. Several factors contribute to the occurrence of accidents. Some of which are human behavior, vehicles condition, weather conditions, road surfaces, and road alignments (vertical and horizontal curves). This research presents empirical research to estimate the 85th percentile operating speed limits. The speed data were obtained using a stopwatch on the selected location along the Agaie-Katcha-Baro Road Agaie, Niger State. Spot speed study was adopted as the method for the research. The method has successfully predicted the 85th percentile speed limit for the Agaie-Katcha-Baro Road Agaie, Niger State. It has established maximum and minimum speed limits for the road and has also shown how inexpensive and quick the stopwatch method is in conducting spot speed studies in Nigerian roads. The findings are hoped to provide a lasting solution towards the national design standard for the highway designer and planner to improving the consistency of geometric design elements of the two-lane highways.

Experimental study and numerical simulation analysis of distortional buckling capacity of stainless steel lipped C-section beams

For S30408 austenitic stainless steel, a mechanical property test of 2.5 mm and 3.0 mm plate and corner regions was carried out, and the mechanical properties and stress–strain curves were determined. On this basis, the distortional buckling capacity tests of 8 stainless steel lipped C-section beams were carried out, and the mechanical performance and failure modes of each specimen were revealed. The load-mid-span vertical displacement curve, load-loading point vertical displacement curve, load-mid-span lateral displacement curve, load-support rotation curve, load-transverse strain curve, distortional buckling load and ultimate bearing capacity of each specimen were determined. A refined finite element model of each specimen was established using the ABAQUS software, and a numerical simulation analysis was carried out. By comparing the finite element results with the experimental results, the accuracy of the finite element model was verified. A parametric analysis was conducted using the validated finite element model. The results showed that the nominal yield strength of the corner region was about 40% ∼ 60% higher than that of the plate region, and the elongation was obviously lower than that in the plate region. In the bearing capacity test, the experimental phenomena of each specimen were illustrated, and the development of distortional buckling wave of the compressed flange was revealed. After distortional buckling, each specimen still had a post-buckling strength. The test results and simulation data were compared with the current standards, which showed that the current standards underestimated the distortional buckling capacity of stainless steel lipped C-section beams.

Risk-Based Calibration of Road Sag Vertical Curve Design Guidelines on Undivided Highways

AbstractSafety in highway geometric design is one of the main goals to be achieved. However, deterministic design criteria do not provide information concerning the risk associated with the design ...

PERENCANAAN GEOMETRIK DAN PERKERASAN LENTUR PADA JALAN NANGAMIRO - JALAN PANCASILA, KABUPATEN DOMPU, NUSA TENGGARA BARAT (STA 0+000 - 8+758)

The road as a transportation system plays an important role, especially in supporting the economy in the Dompu district. Therefore, the planning of the Nangamiro road to the Pancasila road is a road needed by the community and is the main road for the mobility of agricultural / plantation products and also as one of the connecting access roads between Pancasila Village and Nangamiro Village, Pekat District, Dompu Regency to Kananga Village, District Tambora, Bima Regency. The road planning is made with 2 alternatives to choose the best and is planned using flexible pavement. This road planning includes road dimension planning, horizontal alignment and vertical alignment based on the Bina Marga Standard Guidelines for Inter-City Road Geometric Planning Procedures (No.038 / T / BM / 1997), and pavement planning using flexible pavement using the Pd T-01- method. 2002-B Planning Guidelines for Flexible Pavement Thickness. Based on this planning, it is obtained that the track length is 8.539 km with 5 bends of the SCS type with L1 = 190.995 m, L2 = 238.163 m, L3 = 137.031 m, L4 = 174.672 m, L5 = 214.306 m. 2 vertical curves are convex, namely Lv1 = 230.00 m, Lv3 = 230.00 m and 2 vertical curves, namely Lv2 = 230.00 m, Lv4 = 230.00 m, and the thickness of the flexible pavement layer is 7.00 cm with a total cost Rp 144,391,237,000.00,-.

Influence of bolster-hanger length on the dynamic performance of high-speed EMS maglev vehicles

To investigate the dynamic effects of bolster-hanger length on the 600 km/h high-speed EMS maglev vehicles, a dynamic model of three-car trainset is established, considering the kinematic relation of the bolster-hanger mechanism and the active levitation/guidance control system. Model validation is carried out by comparing simulated results with test results of Shanghai high-speed maglev vehicles. Then, the proposed model is used to simulate the dynamic response of maglev vehicles with four different hanger lengths of 0.12, 0.18, 0.24, 0.36 m and passing through the straight track, the horizontal curve and the vertical curve. Simulated results indicate that because of the too short hanger maglev vehicles cannot pass through safely the sharp horizontal curve, and deteriorate the lateral dynamic performance of maglev vehicles on the straight track. The too long hanger may increase the lateral displacement of the carbody and lateral forces of rubber stops of maglev vehicles on the large-radius horizontal curve. The hanger length has little influence on the dynamic response of maglev vehicle on the vertical curve. In sum, the medium-long (0.24 m) hanger can provide a stronger curve negotiation capacity and better ride quality of high-speed maglev vehicles.

Flexural strengthening mechanism of concrete-filled steel tube beam by welding round steel at soffit of the beam

In the present study, the flexural behavior of concrete-filled steel tube (CFST) beams strengthened by welding round steel at the soffit of the beam has been investigated. First, a total of six specimens were tested under four-point bending load, which includes one reference beam and five retrofitted beams strengthened by welding round steel of different diameters at the soffit of the beams. Then, the corresponding nonlinear finite-element models have been developed and calibrated against the experimental results. By combining indoor experiments and numerical simulations, the bending moment versus mid-span curvature curves, the flexural capacities, flexural stiffness, ductility, vertical deflection curves, strain distribution across the cross-section, and neutral axis offset of the test beams have been systematically analyzed. The results show that the welded round steel at the soffit can improve the flexural bearing capacity and stiffness of the CFST beams significantly. This can be attributed to the CFST beams benefitting from the flexural bearing effect of the round steel and the downward offset of the neutral axis which causes more core concrete to be in compression. Further, the larger the diameter of the round steel, the greater the benefit. Finally, comparisons have been made with the flexural stiffness calculated using the existing design codes, such as AIJ standard, BS5400, Eurocode 4 and AISC specification. The comparisons show that the flexural stiffness of the unstrengthened CFST beam can be predicted by AIJ and BS5400 perfectly, whereas those of the strengthened CFST beams can only be accurately calculated by AISC.

Exploring the Need to Model Two- and Multiple-Vehicle Crashes Separately

Single-vehicle crashes have been shown to differ from two-plus vehicle crashes. Several studies have discussed the issues with modeling single-vehicle and two-plus vehicle crashes together. However, none of the empirical studies have attempted to study two-vehicle (2V) and multiple-vehicle (MV), that is, three-plus crash groups, to understand their correlation and influencing factors. This study first investigated whether there is a need to develop separate safety performance functions for 2V and MV crashes, in addition to single-vehicle crashes. Then, the correlation and influencing factors of 2V and MV were evaluated. Three regression models—a correlated bivariate negative binomial regression (BNR) model, an uncorrelated bivariate negative binomial regression (NR) model, and a univariate negative binomial regression (UNR) model, were developed and compared. The analysis was based on the 2011–2015 crashes that occurred on I-4 in Florida. Findings indicated that the BNR model significantly outperformed the NR and the UNR models. The model results suggest that disaggregating 2V and MV crashes while allowing correlation between the groups for the latent effects in the model best describes the data. Traffic volume, posted speed limit, and median type were found significant in contributing to the occurrence of both 2V and MV crashes. Additional contributing factors for 2V crashes included the presence of interchange influence area, and for MV crashes, the presence of a vertical curve and the presence of a horizontal curve. Study findings could assist transportation officials in implementing specific safety countermeasures for road segments identified as hotspots for 2V and MV crashes.

The influence of seed transfer distance on the growth of Calotropis procera (ait) provenances in dry lands of South Eastern Kenya

In a study to domesticate the species Calotropis procera, for wool production in drylands, investigations were done to determine the effects of seed transfer distance on the growth of the species in a typical farm setting. The objectives of the research were to determine the growth of three provenances of C. procera and to determine the influence of seed transfer distance on the growth parameters. Diameter and height data were used to generate horizontal and vertical growth curves respectively and further subjected to Duncan Multiple Range Test (DMRT) to isolate existence of significant differences across the three provenances. Pearson correlation analysis was used to establish existence of relationships across the growth parameters. Results showed that C. procera is a multi-stemmed plant. Duncan Multiple Range Test (DMRT) showed no significant statistical differences (p<0.5) in diameter growth though Pearson correlation analysis, showed strong positive correlations (Pearson, p<0.01) between branching and DBH Test of homogeneity of variances showed significant statistical differences (p<0.5) in vertical growth The study concluded that C. procera is a multi-stemmed plant that can reach a height of 4.48m and a diameter of 7.4cm in two years. It is recommended that C. procera seeds for raising nursery stock should be sourced from the nearest source possible. This will reduce the environmental and climatic effects associated with long distance seed transfers and ensure the species benefits from home-site advantages.

TUNNEL MODELING USING MOBILE MAPPING LIDAR POINTS

Abstract. In this paper, a method to model a tunnel using lidar points is presented. The data used was collected using Leica Pegasus Two Ultimate with a Z+F 9012 Profiler mounted on a mobile platform. The tunnel was approximately 151 m long. Visual inspection of a cross-section of the tunnel showed two rail tracks supported on ballast and sidewalks along both sidewalls of the tunnel. The walls and the ceiling of the tunnel were made of five planar surfaces. The tunnel alignment was straight, without any horizontal or vertical curves. The bearing of the central axis of the tunnel was N12.2oW. The following methodology was developed to model just the planar surfaces of the tunnel by excluding the rails, ballast, sidewalks, powerlines, and other accessories. The entire methodology was divided into three broad parts. In the first part, a model cross-section was created. Since the design plans of the tunnel were not available, the model cross-section polyline was created using mean tunnel dimensions from random cross-section points. The model cross-section consisted of the walls and the ceiling of the tunnel. Points were placed at every 1 cm along the model polyline. Six of the model points that represented the shape of the tunnel were selected as salient points. The lower-left salient point was considered as the seed point. In the second part, to define a reference axis of the tunnel, an approximate centerline was manually defined by selecting points at its start and end. Lidar points within 1 m at the start and the end of the tunnel were modeled using the model points to determine the centroids. The reference axis was determined by connecting the centroids at the start and the end of the tunnel. In the third part, the tunnel points were sliced along the reference axis at 5 cm intervals. The model cross-section was matched to points within each tunnel slice using a three-stage approach. In the first stage, the pattern of salient points was matched to the tunnel points by placing the seed point at every tunnel point location. The distances between salient points and their nearest tunnel points were calculated. Ten sets of tunnel points with the least differences to the salient points were shortlisted. In the second stage, a dense point-to-point matching was performed between the model and sliced tunnel data at the shortlisted points. The shortlisted point location with the least difference between the tunnel and the model points was considered as a match. At this point, the model points were hinged to the tunnel points at the seed point location. Hence, in the last stage, a six-parameter affine transformation was performed to match the model points to the tunnel data. The transformed model points at every 5 cm of the length of the tunnel were considered as current shape of the tunnel.

Calculating TIN-Based 3D Sight Distance and Its Evaluation on Drivers Free-Flow Speed

Sight distance during driving may be limited by side factors such as mountain slopes or trees and buildings in horizontal curves and by the dome of the arc in vertical curves, and the night vision also can be limited in the sag vertical curves by the vehicle’s light. Analyzing driver’s sight distance in the road is very important for traffic safety. In this regard, in order to help the designer, the current rules and guidelines propose the two-dimensional analysis model for the sight distance. In this analysis, the sight distance is calculated separately in the combination of horizontal and vertical curves, and the smallest amount is considered as the sight distance. While, after constructing and operating the road, drivers control their vehicle according to the conditions in their 3D space. Nowadays, given the remarkable advances in computer science, there are many possibilities for 3D modeling of the route. In this research, the goal is to calculate the three-dimensional stopping sight distance at each spatial point by computer modeling the existing roads. The speed of various drivers with conventional riding vehicles under free traffic conditions was obtained by a GPS device. The results showed that, in places such as curves, given the provision of sufficient stopping sight distance, driver’s free-flow speed reduces. Thus, another factor affecting the speed of the drivers is the curvature change rate. Finally, using nonlinear regression modeling a logical relationship was determined and extracted between the three factors of driver’s free-flow speed, 3D stopping sight distance, and curvature change rate of the path.

Calculation model of overburden rock failure volume in mined-out area based on Brillouin optical time-domain analysis technology

The determination of overburden failure volume is a great challenge because of the complexity and concealment of mining fractures. Taking the 61,601 working face of Longwanggou Coal Mine as the engineering background, this paper established a two-dimensional model of 3000 mm × 200 mm × 1350 mm (length × width × height) in the laboratory. By adopting the Brillouin optical time-domain analysis (BOTDA) technology, considering the fiber deformation and the coordination of rock strata, Of deformation and damage state of overburden strata above the mined-out area, discusses the strata deformation partitioning features and characteristics of fiber optic monitoring strain curve partition interaction relations, is derived based on the above theoretical calculation formula of the rock damage volume, comparing the calculated results with measured results, verify the accuracy of volume calculation formula of mined-out area. The results show a good correspondence between the strain zoning characteristics monitored by optical fiber and the deformation zoning characteristics of overburden. Based on considering the discordant deformation between the overlying rock mass and the optical fiber sensor, the range and degree of overlying mining rock can be obtained through the inversion of the horizontal optical fiber monitoring results to reflect the position and degree of rock strata movement and deformation with the optical fiber. By analyzing the development process of the vertical fiber optic strain curve, it can be found that the rock strata with different propelling distances and different heights bear different tensile stresses, which have remarkable range characteristics. By comparing the results of the calculation model proposed in this paper with the monitored values of the model, it is found that the void volume size of goaf is the same, and the relative error is less than 9%. The results show that the model is reliable in calculating the failure volume of overburden rock in goaf.

Kinematic gait characteristics of straight line walk in clinically sound dairy cows.

The aim of this study is to describe the kinematic gait characteristics of straight line walk in clinically sound dairy cows using body mounted Inertial Measurement Units (IMUs) at multiple anatomical locations. The temporal parameters used are speed and non-speed normalized stance duration, bipedal and tripedal support durations, maximal protraction and retraction angles of the distal limbs and vertical displacement curves of the upper body. Gait analysis was performed by letting 17 dairy cows walk in a straight line at their own chosen pace while equipped with IMU sensors on tubera sacrale, left and right tuber coxae (LTC and RTC), back, withers, head, neck and all four lower limbs. Data intervals with stride by stride regularity were selected based on video data. For temporal parameters, the median was calculated and 95% confidence intervals (CI) were estimated based on linear mixed model (LMM) analysis, while for limb and vertical displacement curves, the median and most typical curves were calculated. The temporal parameters and distal limb angles showed consistent results with low variance and LMM analysis showed non-overlapping CI for all temporal parameters. The distal limb angle curves showed a larger and steeper retraction angle range for the distal front limbs compared with the hind limbs. The vertical displacement curves of the sacrum, withers, LTC and RTC showed a consistent sinusoidal pattern while the head, back and collar curves were less consistent and showed more variation between and within cows. This kinematic description might allow to objectively differentiate between normal and lame gait in the future and determine the best anatomical location for sensor attachment for lameness detection purposes.

Brief design and numerical calculations for a secondary road

Based on the traffic volume survey, the standard traffic volume conversion is considered, and then the road traffic volume is predicted. Through the calculation, the maximum annual average daily traffic volume in the design life is obtained, and then the road grade and design speed of the design road are determined. The Annual Average Daily Traffic (AADT) is converted into Directional Design-Hour Volume (DDHV), and then the number of lanes of the road is determined. Collect the terrain data of the route area through the field survey, and then carry on the interior design. The route schemes are compared and the optimal route scheme is selected. AUTOCAD and a professional road design software were used to assist in the design of road line selection, horizontal curve design, vertical section design, cross section design and drainage design. Through the calculation, the design parameters such as the maximum synthetic slope, the average slope and the minimum length of superelevation transition section are obtained. Afterwards, the parameters in horizontal curve, vertical curve and superelevation-widening were checked manually.

Assessment of road safety parameters in the city of Kigali, Rwanda

Increase in vehicular population has led to increase in road crashes. This is particularly very evident in low- and middle-income countries. Rwanda is no exception to this problem. While various factors influence the occurrence of a crash, it is argued that road design can make roads either safe or unsafe to drive. This research examines geometric parameters of roads in the City of Kigali, with emphasis on checking their safety parameters in comparison with design standards of AASHTO 2011. The case study of this research was „KN 123 St‟, a two-lane asphalt road located in the center of the City of Kigali. Road parameters like lane widths, curve radii, super-elevation, sight distances and slope grades were examined. The research found various areas of improvement, inconsistencies and non-conformities. The findings established a clear relationship between ignored safety parameters during design and construction, and road crashes that happened on specifically identified hazardous spots. For instance, there is an extreme abrupt change in lane widths over the whole length at a rate of 74%. Unsafe sharp curves make half of all evaluated horizontal curves. Curves with the smallest radii have already recorded many crashes. The study found that super-elevation values have been inadequately computed, designed, and constructed with an average variance of 5%. About 80% of assessed vertical curves had insufficient stopping sight distance and 90% of headlight sight distance likewise. Apart from geometric parameters, high operating speeds of car drivers and motorcyclists, lack of shoulders, lack of zebra crossings and left sidewalk were found as extra causes of traffic injuries. While widening of the road could potentially help meet most safety parameters, it is arguably expensive and unrealistic. Therefore, this study recommends speed governance, forgiving roadside features, traffic signalization, and road markings as tools to alert drivers where most crash-prone areas are.
 Keywords: Road safety, Geometric design, Safety assessment, Road Crashes, AASHTO 2011

Feasibility study of highway alignment design controls for autonomous vehicles

In recent years, the development and testing of autonomous driving technology have become widespread around the world. However, due to differences in perception abilities between autonomous vehicles and human drivers, the current geometric design controls for highway alignments, designed for the human driver, may not be applicable to the autonomous vehicle (AV). Few studies, however, have systematically investigated the design controls for autonomous vehicles, though we face full driving automation in the next few decades. Because the range of modern AV sensors reaches 250 m, with expected further improvements in the near future, there is a need to determine how the sensors’ perception field and perception-reaction time may affect the current road design standards developed for human drivers. This study therefore tested the feasibility of the current design controls for fully-autonomous vehicles by separately computing controls for vertical alignments and combined horizontal and vertical alignments, considering the AV’s perception abilities of perception-reaction time (PRT), sensor height, and upward angle from the horizontal. The required stopping sight distance (SSD) and minimum length of sag and crest vertical curves were derived and compared with those for human drivers. Computations for combined alignments were based on Green Book coordination guidelines: as the minimum length of horizontal curve can be used for alignments adhering to guidelines, preview sight distance (PVSD) was computed for alignments that do not. Results showed that 1) AV-based design controls on vertical curves were more tolerant than those based on human drivers; and 2) the dominating criterion of sag vertical curve design control was comfort for autonomous vehicles, versus required SSD for human drivers.

Assessment of Young Drivers’ Driving Behaviour and Driving Speed along Horizontal and Vertical Alignments

Young drivers are more likely to experience car crashes as they tend to have risky driving behaviours. This study aims to assess young drivers’ driving behaviour and driving speed along the horizontal and vertical alignments of roads. The 20 young drivers who participated in this study were asked to complete a self-reported assessment (Driver Behaviour Questionnaire) and then invited for an on-road driving assessment during daytime and night-time, along horizontal and vertical road alignments at a selected route in Skudai, Johor. The results from the Driver Behaviour Questionnaire revealed that distractions during driving was the most frequently reported behaviour that caused car crashes amongst young drivers, followed by error and violation. Speed profile was found to be higher during daytime when compared to night-time. A significant difference in speed between male and female drivers was noted at horizontal curves during daytime and vertical curves during night-time. The study concluded that such aberrant driving behaviours would have an impact on the driving performance, particularly on horizontal and vertical curves.