Road Network Design Research Articles

Distance-Measure Impacts on the Calculation of Transport Service Areas Using GIS

Access coverage is important in public transit planning, as this is the means by which service is provided to riders. In fact the proximity of demand (population and employment) to stops or stations on the network to a great extent explains its greater or lesser usage by potential users. Coverage of service areas can be delineated by GIS through the creation of buffers around transit facilities based on Euclidean (straight-line) distance. A second method is based on calculations of distances along a street network (network distance). The choice of the distance calculation method affects significantly the final results in terms of population covered. This paper assesses the overestimation of the straight-line-distance method, which is the most widely used in coverage analysis, by comparing it with that of network distances. It investigates systematically the factors influencing this overestimation, such as the density of stops or stations, the coverage distance thresholds and the characteristics of the area analysed (street-network design, barriers, and population distribution in the neighbourhood of the bus stop or station). Finally, it concludes that the network-distance method provides systematically better estimates of transit ridership than the Euclidean distance method.

Improved road network design models with the consideration of various link patterns and road design elements

The success of an automatic road network layout over steep terrain mainly depends on the model design. Most previous models have used a grid representation that considers only eight adjacent cells when evaluating feasible road links. Here, we present improved models and alignment constraints mapped on a mathematical graph for better designs that are more applicable under field conditions. We have refined the link pattern by considering up to 48 neighbouring cells and have introduced 16 directional classes per grid cell. Optimization techniques, such as shortest path, minimum spanning tree, and Steiner minimum tree algorithms, are used on the graph to derive a road network that is optimal in terms of its construction costs. These improved models have been applied to different mountainous project areas. Our results show that, by considering various link patterns and alignment constraints, one can determine more appropriate and cost-effective locations for road networks, especially in steep terrain.

The anatomy of the safe and social suburb: An exploratory study of the built environment, social capital and residents’ perceptions of safety

This study explored the relationship between social capital and aspects of the built environment, focusing in particular on the walkability of suburbs as determined by street network design and the mix of land uses. We measured social capital and feelings of personal safety in 335 residents of three suburbs in metropolitan Perth, WA, and collected objective and perceived data on the built environment. After adjustment for demographic factors, the built environment was found to have a significant but small effect on social capital and feelings of safety, particularly in relation to the number and perceived adequacy of destinations. A high level of neighbourhood upkeep was associated with both higher social capital and feelings of safety.

Optimal design of signal-controlled road network

An optimal design of signalized road network is considered where total travelers’ delay is minimized subject to user equilibrium flow. This problem can be formulated as an optimization problem by taking the user equilibrium traffic assignment as a constraint. In this paper, a projected conjugate gradient method is presented to solve the signalized road network problem with global convergence. Numerical examples are investigated on simple grid road network. As it shows, the proposed method achieved substantially better performance than did traditional approaches when solving the signalized road network design problem with equilibrium flows.

A non-smooth model for signalized road network design problems

A signalized road network is considered where the set of link capacity expansions and signal setting variables are simultaneously determined. This paper addresses a new optimization scheme for a signalized road network design problem (SRNDP). A SRNDP can be formulated as a mathematical program with equilibrium constraints (MPEC) where user equilibrium is expressed as a variational inequality problem. Due to non-differentiability of the perturbed solutions in equilibrium constraints, a non-smooth model is established. A bundle subgradient projection (BSP) method is presented with global convergence. Numerical calculations are conducted on a real data city road network and large-scale grid networks where promising results are obtained.

Two-way road network design problem with variable lanes

This paper studies a new form of transportation network design problem. In urban transportation network, unreasonable phenomenon can occur in certain traffic period (e.g. on/off duty period), which demonstrates that the flows of opposite directions on a two-way road are seriously asymmetric; one traffic link of a two-way road congest heavily but the other is hardly used. In order to reduce transportation congestion and make full use of the existing road resources, we propose a lane reallocating approach in peak period, and establish a discrete bi-level programming model for the decision-making. Then, based on particle swarm optimization (PSO) technique, a heuristic solution algorithm for the bi-level model is designed. Finally, the lane reallocating approach is demonstrated through a simple transportation network.

AN INTEGRATED MODEL FOR OPTIMIZING RURAL ROAD NETWORK AND PUBLIC FACILITY LOCATION IN DEVELOPING COUNTRIES

In many developing countries, the poor geographical accessibility has made rural residents isolated from opportunities which improve quality of life. The objective of this study is to provide an integrated model for optimal road network and multi-type public facility location design considering budget constraint. The model is simulated with the real road network in puok district, Cambodia. It is found that investment in many small size facilities distributed among villages along with a provision of a good basic earth road seems to be the most cost-effective approach in the study area.

Heuristics for urban road network design: Lane layout and signal settings

This paper concerns the urban road network design problem. In urban areas supply has usually been unable to keep pace with increasing demand: the only possibility is often to reorganise the current supply configuration in order to use existing resources efficiently. Thus, in urban areas signal settings and network topology (in particular lane layout) are the two major factors that can be handled by design models. Methods for the combined design of signal settings and topology are proposed in this paper. All the methods proceed in two stages: the first deals with integer variables (topology), while the second deals with continuous variables (signal settings). Some metaheuristics (Hill Climbing, Simulated Annealing, Tabu Search, Genetic Algorithms and Path Relinking) are specified for the topology design stage, and they are used singularly or jointly. The continuous part of the solution, with fixed topology is optimized through an algorithm for asymmetrical deterministic equilibrium assignment. This paper focuses on evaluating performances obtained by all the different algorithms proposed for the topology design stage. The algorithms are compared by applications to real networks, and some conclusions are drawn about their efficiency.

The multi-criteria road network design problem in an urban area

In this paper, urban network design is analysed through a heuristic multi-criteria technique based on genetic algorithms. Both network layout and link capacity (link layout and traffic lights) are optimised. Different optimisation criteria are included for users, non-users and public system managers. Demand is considered elastic with respect to mode choice; both morning and afternoon peak periods are taken into account. In addition, choice of parking location is simulated. The procedure is applied to a test and to a real transportation system.

A Topological Method to Choose Optimal Solutions after Solving the Multi-criteria Urban Road Network Design Problem

The paper proposes and applies a method for systematically sorting and reducing the number of different possible solutions to a network design problem (NDP). This is achieved first by defining a topological similarity measurement and then by applying cluster analysis. The NDP can be derived from the scientific literature. In general, the method consists of some models and subsequent algorithms that generate different solutions (enumerative, branch and bound, genetic, expert panel, ...) and evaluate for each solution an objective function (with deterministic or stochastic network assignment and with elastic or inelastic demand). The NDP, mainly in urban areas, needs multi-criteria evaluation and in each case a large set of non-dominated solutions is generated. In this paper, in order to select solutions and identify latent optimal network layouts, cluster analysis is carried out. The methodology utilises a “cluster” formation in relation to the solution topology and a “best” (representative) solutions extraction in relation to the criteria values. It can be utilised after solving the existing multi-criteria NDP and in other network problems, where the best solutions (for global or local network layouts) are extracted (with respect to the network topology) from a large set. The method is applied in a test system and on different real networks in two Italian towns, in order to analyse the goodness of the solution algorithm and assess its possible application to different networks.

Possibilities of Using the Direct Runoff Model KINFIL for a Road Network Design

The paper provides a practical implementation of the hydrological model KINFIL to be used for design­ing an optimal road density system in areas where agricultural or forestry production does not play an important role. In particular, such a road system project is based on the physiographic characteristics of land. Input data for a direct runoff analysis are computed in relation to the geometric parameters of upstream sub-catchments using the method of maximum daily precipitation reduction. Computed direct runoff discharges depend mainly on soil and vegetation conditions. Besides the soil type characteristics, the length and the angle of hill slopes to be drained by a road drainage system are major parameters determining the road density. These discharges are further assessed for road drain capacities designed according to the Czech Standard System (ČSN).

Pessimistic Equilibrium Flow and Its Network Design Implications

Quality of service in urban transportation network is very important to the users of this network. Travel time in street networks is one, very important, aspect of this service, particularly for trips with purposes such as work or school. A conservative route choice concept based on a pessimistic view of travel time has been proposed to render a pessimistic equilibrium flow (PEF). This flow is different from a user equilibrium flow (UEF), particularly in congested networks, and has sometimes a lower total travel time than UEF. A street network design problem has been proposed to take into account the travel time fluctuations (or service quality) in the network. This design model is based on PEF and is called pessimistic network design (PND) model. It is shown by an example network that an implication of PEF consideration in a PND model is that projects with lower potential in getting congested are chosen as compared with the conventional network design problem.

Non-motorized transportation in four Shanghai districts

Shanghai is well known for a high level of non-motorized travel, in particular by bicycle. This research investigated firstly whether significant differences in the use of non-motorized transportation between areas of the city can be attributed to particular features of the local environment, in particular road network characteristics and design; secondly, the extent to which personal and household characteristics contribute to this variable use of foot and bicycle modes of travel. The most recent trips and daily repeated trips of 1,811 individuals were collected in four districts in Shanghai in a one-week period. Distances were extracted from a GIS while regression analysis examined the significance of district, age, income, trip purpose and mode choice in the distance travelled and in the proportion of travel by non-motorized means. District accounted for up to 22% of variance in the proportion of non-motorized travel. Differences in the allocations to motorized and non-motorized modes between districts were significantly related to block structure and road density but not to public transportation provision. There were also significant differences in travel distances by mode and trip purpose. Finally, age, income, household composition and type of employment had very minor effects on travel mode and travel distance by non-motorized modes.

A GRASP and Path Relinking Heuristic for Rural Road Network Development

This paper presents a model for rural road network design that involves two objectives: maximize all season road connectivity among villages in a region and maximize route efficiency, while allocating a fix budget among a number of possible road projects. The problem is modeled as a bicriterion optimization problem and solved heuristically through a greedy randomized adaptive search procedure (GRASP) in conjunction with a path relinking procedure. The implementation of GRASP and path relinking includes two novel modifications, a new form of reactive GRASP and a new form of path relinking. Overall, the heuristic approach is streamlined through the incorporation of advanced network flow reoptimization techniques. Results indicate that this implementation outperforms both GRASP as well as a straightforward form of GRASP with path relinking. For small problem instances, for which optimality could be verified, this new, modified form of GRASP with path relinking solved all but one known instance optimally.

Design of forest road network in relation to all-society functions of forests

The basic condition of forest management development is the accessibility of the forest. A design of the forest road network in relation to all-society functions of forests has been made in the catchment of the Vilčok stream. The catchment is situated in Protected Landscape Area Beskydy. The method Quantification and quantitative evaluation of functions of forests as a basis for their evaluation (Vyskot et al. 2003) was used for the design. This method can be applied to road planning. It can serve as another component in the decision-making process of the planning of forest road construction.

Fashioning one-way urban road network design as a Module Orientation Problem

Conversion of 2-way roads to 1-way roads or vice versa is not an unusual practice in the pragmatic field of transport engineering. However, there have been few if any mathematical theories developed to investigate the optimal layout of the road network during the conversion of 2-way roads to 1-way roads. This paper discusses fashioning 1-way urban road network design as a Module Orientation Problem (MOP), thereby suggesting various solutions employed in the MOP could be used in the design of 1-way urban road networks. As an illustration, the graph model approach provided by Cheng et al. (1991) is used to formulate the 1-way urban road network design as an MOP. Results obtained are run and further validated using a traffic simulation package, Paramics.

A decision support system for assessing alternative projects for the design of a new road network: methodology and application of a case study

This study aims to offer an applicable evaluation framework for assessing project alternatives by employing different multicriteria evaluation methods as a tool to reduce conflicts in a decision making process. The first part of the paper consists of a brief survey of the great diversity of modern assessment methods that have been developed in recent decades. This helps to provide a perspective for procedural types of decisions in which various qualitative and quantitative aspects are incorporated. The paper initially focuses on three recently developed techniques: Regime analysis, the Analytical Hierarchic Process (AHP) method and the Flag model. It advocates a merger of these methods. In the second part of the paper, the above-mentioned multicriteria methods are applied to a real-world case concerning the design of a new road network in the area of the Cilento National Park in Italy.

Benefit distribution and equity in road network design

In the classical continuous network design problem, the optimal capacity enhancements are determined by minimizing the total system cost under a budget constraint, while taking into account the route choice behavior of network users. Generally the equilibrium origin–destination travel costs for some origin–destination (O–D) pairs may be increased after implementing these optimal capacity enhancements, leading to positive or negative results for network users. Therefore, the equity issue about the benefit gained from the network design problem is raised. In this paper, we examine the benefit distribution among the network users and the resulting equity associated with the continuous network design problem in terms of the change of equilibrium O–D travel costs. Bilevel programming models that incorporate the equity constraint are proposed for the continuous network design problem. A penalty function approach by embodying a simulated annealing method is used to test the models for a network example.

Reducing sediment inputs to Scottish streams: a review of the efficacy of soil conservation practices in upland forestry

The historical process by which a soil conservation strategy has evolved within the UK forestry industry is briefly reviewed. Particular attention is given to the development of practical and effective guidelines to prevent both soil damage and sediment entering water courses. It is concluded that the ‘Forest and Water Guidelines’, together with other forest industry manuals, largely provide adequate protection for aquatic habitats from pre-afforestation cultivation and from harvesting activities. The problem of soil erosion owing to ploughing of open furrows has largely been obviated by improved drainage network design coupled with the use of vegetated buffer strips and sediment catchpits. Alternative site preparation techniques, such as ‘moling’ or ‘dolloping’ of afforestation sites, are now preferred. However, the effects on slope hydrology and the improved soil conservation associated with these methods require quantifying. Additional understanding of effective buffer strip function, for example, on a variety of slope angles, soil types and vegetation associations would be beneficial. The design of forest roads and the associated network of drains, culverts and sediment catchpits is addressed in forestry guidelines. Future potential in this area may involve the use of Geographical Information Systems in the effective design of road networks which minimise adverse effects on slope hydrology. Similarly computer simulation of flow routing might aid in the design of road drain networks. At the more local scale there remains scope for further research aimed at minimising soil disturbance by machinery. Consideration should also be given to the long-term sustainability of the soil structure through second and subsequent crop rotations.

The design of a terminal network for intermodal transport

A model called TERMINET 1 model has been developed to determine locations and capacities of road and rail terminals where transshipment of load-units between road vehicles and trains takes place. The model consists of a traffic conversion method which translates freight flows from tonnes to numbers of load-units as well as a freight flow consolidation method using existing assignment techniques. The TERMINET model examines the possible binding effect of terminal infrastructure and investigates the influence of the cost structure of intermodal transport which strongly determines the possible modal-shift from road to intermodal transport. The TERMINET model makes it possible to determine interactively or automatically inland terminal locations for transshipment of load-units between road vehicles trains. The influence of train length on terminal locations, terminal capacities and network load may be calculated. Besides these capabilities it is also possible to determine the overall system performance in tonnes, tonne-kilometres, TEUs and numbers of trains. The TERMINET model has been applied to the design of an inland road and rail terminal network in the Netherlands to be used in an intermodal road and rail freight transport system for international and Dutch domestic freight flows for the year 2015. The cost structure of intermodal transport has been examined. Cost calculations have been made to examine the effect of zero or complete passing on of external and infrastructure costs to both the road and rail mode. Furthermore, the effect of the maximum use of intermodal transport on the reduction of the growth of road transport has been examined.