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When a road design solution is quite out of standards for the presence of insurmountable constraints, there is the need for an objective procedure aimed at achieving a certain level of safety for drivers. To avoid issues on judicial responsibility, designers aim to fully satisfy the existing standards, possibly without any exception. Traditional methodologies based on previous experience or road administrators' guidelines generally caused problems due to the high subjectivity involved in the analysis. In this paper, to overpass these issues, a rational procedure based on vehicles telemetry data in a simulated environment is proposed. This process, through synthetic indices, allows the analysts to compare two road geometries, similar but different, because one includes curves with shorter residual circular arcs than threshold values imposed by Italian standards. The main results, derived from a two-way ANOVA with subsequent contrast analysis, suggest that a certain deviation respect to the standards did not determine any decay in the driver's performance. Compared to the existing literature, in this study, a full objective procedure was proposed, based on a totally new indicator, which can be easily adapted to any context, involving driver, road and vehicle at the same time. [ABSTRACT FROM AUTHOR]

In this paper the use of lime stabilized subgrade for low volume roads in two regions with high mountains and different frost penetration conditions in Türkiye was investigated in terms of design, performance, and cost. Pavements on unstabilized and stabilized subgrade were designed for two regions (Izmir and Van), covering all climate variations. The resilient modulus of the lime stabilized subgrade with different soil pulverization levels for non-freezing and freezing conditions were taken from a previous laboratory study. Frost effects were considered in pavement design using two different approaches, including limited subgrade frost penetration method and reduced subgrade strength method. Detailed application and evaluation were performed for all steps. Lime stabilized subgrades significantly reduced the thickness of base courses, and the benefit of lime stabilization was highly dependent on soil pulverization level. A detailed cost analysis on the unstabilized and stabilized cases found that the use of lime stabilization in the subgrade provided significant initial cost savings. Comparative analysis by using the AASHTO (1993) method and KENPAVE software, and quantity effect of soil pulverization level on the performance of low volume roads from a service life perspective, show that subgrade resilient modulus can be estimated. It is also possible to make correct performance estimation in the field. The results of the study show that lime stabilization is a good solution for low volume roads in the mountainous regions of Türkiye. [ABSTRACT FROM AUTHOR]

The construction and operation of linear infrastructure has major impacts on biodiversity through loss of habitat, increased mortality and loss of connectivity. In particular, minimising the impact of roads which pass through ecologically sensitive areas on surrounding species at the construction and operational phases is critical for conservation. However, potential impacts are rarely known perfectly at the construction phase and early in the operational phase. To address this problem, a company could build flexibility into road operation so that it can respond rapidly to future ecological impacts if necessary. In this paper we analyse the value of this flexibility using stochastic dynamic programming and use the results to guide a global search algorithm to find high value roads in the region. We consider flexibility in terms of the proportion of traffic volume routed along the road, with the remainder passing along an existing higher-cost, lower-impact road. We applied this to an example scenario where a road must be routed through a region with a vulnerable species present. By incorporating flexibility, the proposed model was able to find a road that met a desired ending population of animals and was more valuable than roads found under existing design alternatives. [ABSTRACT FROM AUTHOR]

This paper presents a new algorithm to build feasible solutions to a MILP formulation of the vertical alignment problem in road design. This MILP involves a large number of special ordered set of type 2 variables used to describe piecewise linear functions. The principle of the algorithm is to successively solve LPs adapted from the MILP by replacing the special ordered set of type 2 constraints by linear constraints. Proof that the solutions to the successive linear relaxations of the MILP converge to a feasible solution to the MILP is provided. Numerical results emphasize that the algorithm performs better than CPLEX for large scale vertical alignment problems. [ABSTRACT FROM AUTHOR]

Because of the singular form and low flexibility of the clothoid as a highway transition curve in highway horizontal alignment, the K-curve, whose ratio of the chord-tangent angle to the tangential angle at any point is fixed, was proposed in a previous work, including the corresponding parametric equations and basic characteristics, and its high flexibility and various shapes were proved. Here, the application and verification of the K-curve in highway alignment is further studied. The solution methods of the K-curve for different connections are given. Through theoretical calculations and specific real-world examples, the geometric positions and lateral forces of the K-curve and the clothoid under different connection conditions are compared. The results show that the difference between the K-curve and clothoid in the above two aspects under a straight line-to-circle connection is greater than that under a circle-to-circle connection as an egg curve, and although the lateral force coefficient of the K-curve is smaller than that of the clothoid, the K-curve suffers from rapid change in the lateral force coefficient and a higher lateral acceleration change rate. Finally, the application conditions of the K-curve for highway alignment design are given with consideration of the centrifugal acceleration change rate. [ABSTRACT FROM AUTHOR]

When building a road, it is critical to select a vertical alignment which ensures design and safety constraints. Finding such a vertical alignment is not necessarily a feasible problem, and the models describing it generally involve a large number of variables and constraints. This paper is dedicated to rapidly proving the feasibility or the infeasibility of a Mixed Integer Linear Program (MILP) modeling the vertical alignment problem. To do so, we take advantage of the particular structure of the MILP, and we prove that only a few of the MILP's constraints determine the feasibility of the problem. In addition, we propose a method to build a feasible solution to the MILP that does not involve integer variables. This enables time saving to proving the feasibility of the vertical alignment problem and to find a feasible vertical alignment, as emphasized by numerical results. It is on average 75 times faster to prove the feasibility and 10 times faster to build a feasible solution. [ABSTRACT FROM AUTHOR]

The problem of moving a commodity with a given initial mass distribution to a pre-specified target mass distribution so that the total work is minimized can be traced back at least to Monge's work from 1781. Here, we consider a version of this problem aiming to minimize a combination of road construction and transportation cost by determining, at each point, the local direction of transportation. This paper covers the modeling of the problem, highlights how it can be formulated as a material distribution topology optimization problem, and shows some results. [ABSTRACT FROM AUTHOR]

The paper presents an original design method of vertical alignment of road routes. It involves the use of the so-called general or universal transition curves. These curves describe the entire curvilinear transition between two straight lines using a single equation. They also have only one curvature extremum, which is of great practical significance. By using general transition curves, it is possible to obtain a completely curvilinear course of vertical alignment ensuring full smoothness at the connection points of each curve. The paper presents a methodology of creating appropriate approximation equations for longitudinal profile points as well as their development using the method of least squares in order to determine the parameters for optimum vertical alignment. The proposed approach reflects the principles of the so-called polynomial routing and makes it possible to create vertical alignment that may be composed of both general transitional curves, as well as straight line sections. Numerical studies of several longitudinal profiles on the site have shown that the proposed approach allows for a better fit to the vertical terrain than traditional design methods of vertical alignment, i.e. using tangent polygon of parabolic arcs. [ABSTRACT FROM AUTHOR]

This work investigates the role of materials selected for different urban surfaces (e.g. on building walls, roofs and pavements) in the intensity of the urban heat island (UHI) phenomenon. Three archetypal street-canyon geometries are considered, reflecting two-dimensional canyon arrays with frontal packing densities (λ) of 0.5, 0.25 and 0.125 under direct solar radiation and ground heating. The impact of radiative heat transfer in the urban environment is examined for each of the different built packing densities. A number of extreme heat scenarios were modelled in order to mimic conditions often found at low- to mid-latitudes dry climates. The investigation involved a suite of different computational fluid dynamics (CFD) simulations using the Reynolds-Averaged Navier-Stokes equations for mass and momentum coupled with the energy equation as well as using the standard k-ε turbulence model. Results indicate that a higher rate of ventilation within the street canyon is observed in areas with sparser built packing density. However, such higher ventilation rates were not necessarily found to be linked with lower temperatures within the canyon; this is because such sparser geometries are associated with higher heat transfer from the wider surfaces of road material under the condition of direct solar radiation and ground heating. Sparser canyon arrays corresponding to wider asphalt street roads in particular, have been found to yield substantially higher air temperatures. Additional simulations indicated that replacing asphalt road surfaces in streets with concrete roads (of different albedo or emissivity characteristics) can lead up to a ~5 °C reduction in the canyon air temperature in dry climates. It is finally concluded that an optimized selection of materials in the urban infrastructure design can lead to a more effective mitigation of the UHI phenomenon than the optimisation of the built packing density. [ABSTRACT FROM AUTHOR]

The role of engineering geology in the final design and construction of a road crossing the Blue Nile (Abay) gorge in Ethiopia is described. This new road between Mekhane Selam and Gundewein is a strategic link in the Ethiopian road network and encounters very steep and difficult terrain that poses significant engineering geological challenges. Remote sensing, landscape modelling, reference condition classification, and conventional field mapping have been applied to assist in the finalisation of the alignment, the prediction of ground conditions for earthworks design, and the implementation of slope and drainage protection works. The approach adopted serves as a blueprint for other road construction and improvement projects in the region though limitations exist with respect to the prediction of variable volcanic rock sequences at depth without the benefit of ground investigation boreholes. Although ground conditions different from those predicted have been exposed along 15 % of the alignment, these have been of relatively minor significance and have necessitated unanticipated remedial action affecting less than 2 % of the alignment in the gorge. Thus far, the main damage to the road from geohazards has been caused by road-related effects, including the concentration of road drainage below culverts and seepages from broken and blocked side drains. The susceptibility of the terrain to uncontrolled runoff is such that preventative and reactive maintenance will be required throughout the lifetime of the road. [ABSTRACT FROM AUTHOR]

The present article offers analyses of important issues concerning design of vertical arcs by means of polynomial transition curves. In particular, two families of polynomial transition curves are considered, both of which are marked by versatility in shaping their geometry. This is an effect of a wide range of acceptable values that can be assumed by the parameter which governs mutual relations between the minimum radius, abscissa of the end point of the curve, and the slope of the tangent in the starting point. The article describes due procedures for designing vertical arcs, and compares them with traditional arcs which are formed by means of a second-degree parabola. The presented analyses lead to conclusions which have implications also for possible modernizations of already existing routes that may involve reconstruction of vertical arcs by means of polynomial transition curves. [ABSTRACT FROM AUTHOR]

Roads with high traffic volumes are a source of animal mortality, can disrupt normal animal movements and dispersal, and may represent a potentially serious threat to wildlife population stability and viability. Retrofitting existing structures built for other purposes (e.g., drainage culverts or small below-grade access roads) to facilitate wildlife crossing by animals and to reduce mortality may be expensive if modifications to the existing structures themselves were involved. However, the environmental context surrounding these structures may influence the willingness of animals to cross, and management of some of these attributes may enhance the attractiveness of these structures. Culverts and underpasses are two common structures along roads in Portugal. We quantified the response of small and medium-sized carnivores to the presence of both types of existing passages by determining: (1) frequency of use; (2) whether use differed by type of passage, and if so; (3) by examining if associated environmental attributes might explain the differences observed. We surveyed 57 different passages along 252 km of highway with a total sampling effort of 2,330 passage trap-days. The mean passage rate for carnivores combined was 0.7 complete passages per crossing structure per day. Crossings by weasel, polecat, otter, and wildcat were infrequent or absent. Red fox, badger, genet and Egyptian mongoose used the crossing structures regularly and without obvious preference; stone marten preferred underpasses. Regression analyses showed the frequency of use by carnivores varied with structural, landscape, road-related features, and human disturbance with 17 of 26 (65%) attributes being significant. Larger passages with vegetation close to the passage entrances, favorable habitat in the surrounding area, and low disturbance by humans were important key features to regular use by the guild of species studied. Mitigation planning in areas with ecological significance for carnivores will be beneficial. Structural attributes and human disturbances are more difficult or expensive to change, even though related significantly to crossing use. Management of vegetation at passage entrances and restricting human use near passages in carnivore suitable areas may substantially improve crossing attractiveness for the guild of carnivore species. [ABSTRACT FROM AUTHOR]

Advances in personal computers (PCs) have increased interest in computer-based road-design systems to provide rapid evaluation of alternative alignments. Optimization techniques can provide road managers with a powerful tool that searches for large numbers of alternative alignments in short spans of time. A forest road optimization model, integrated with two optimization techniques, was developed to help a forest road engineer in evaluating alternative alignments in a faster and more systematic manner. The model aims at designing a path with minimum total road costs, while conforming to design specifications, environmental requirements, and driver safety. To monitor the sediment production of the alternative alignments, the average sediment delivered to a stream from a road section was estimated by using a road erosion/delivery model. The results indicated that this model has the potential to initiate a new procedure that will improve the forest road-design process by employing the advanced hardware and software capabilities of PCs and modern optimization techniques. [ABSTRACT FROM AUTHOR]

It is very important for managers to plan a road network that meets all the requirements for tourism development and management. The aim of this study was to evaluate and modify an existing road network for tourism purposes in the Arasbaran protected area. First, the map layers of effective criteria were prepared in GIS and were standardized by a fuzzy logic approach and finally combined considering their relative importance weights obtained through pair-wise comparison technique. A suitability map was then acquired. After that, 14 different scenarios of road network were designed to access the recreational area using PEGGER extension in ArcView. Then, they were evaluated in terms of technical, environmental, and socio-economic criteria to achieve the optimal-designed road network. Moreover, the existing road network was modified according to the optimal-designed road scenario. Finally, a modified version of the existing road network was proposed for tourism development and management in the Arasbaran region. Regarding the results, the slope criterion with a value of 0.289 was identified as the most important factor in providing a suitability map for road planning. The seventh scenario, with a road density of 3.34 m ha−1 and accessibility (hard) of 64.68%, was chosen as the optimal option to modify the existing road network due to the best performances in terms of minimum costs and environmental impacts on the basis of the highest value per unit length (72.26). According to the assessments and chi-square test comparison, the optimal-designed road network and the proposed road network were identified as better alternatives compared to the existing road. Based on this work, it can be concluded that the combination of GIS-MCDM approaches can properly assist in tourism planning and management. [ABSTRACT FROM AUTHOR]