User Delay Costs Research Articles

An Improved Gravitational Search Algorithm for Task Offloading in a Mobile Edge Computing Network with Task Priority

Mobile edge computing (MEC) distributes computing and storage resources to the edge of the network closer to the user and significantly reduces user task completion latency and system energy consumption. This paper investigates the problem of computation offloading in a three-tier mobile edge computing network composed of multiple users, multiple edge servers, and a cloud server. In this network, each user’s task can be divided into multiple subtasks with serial and parallel priority relationships existing among these subtasks. An optimization model is established with the objective of minimizing the total user delay and processor cost under constraints such as the available resources of users and servers and the interrelationships among the subtasks. An improved gravitational search algorithm (IGSA) is proposed to solve this optimization model. In contrast with the other gravitational search algorithm, the convergence factor is introduced in the calculation of the resultant force and the crossover operation in a genetic algorithm is performed when generating the new particles during each iteration. The simulation results show that the proposed IGSA greatly improves the system performance compared with the existing algorithms.

Detour-Impact Index Method and Traffic Gathering Algorithm for Assessing Alternative Paths of Disrupted Roads

Infrastructure plays a key role in society. Recent collapses of bridges have underlined their importance for road functionality, causing disruptions to commuters and emergency vehicles. Major issues arise on rural roads, where the lack of redundancy leads to the isolation of entire communities. Actual approaches to assess the resilience of countryside roads rely on the availability of specific datasets, limiting their practical application; this issue is typically related to traffic data. This research aims to propose innovative algorithms to assess the road network’s vulnerability in rural areas, including a novel traffic data collection process and its calibration. The aggregate metric is called Detour-Impact Index (DII) and compares user costs before and after a disruptive event. The method uses traditional network-impact metrics in combination with a new algorithm that allows us to gather quantitative traffic data starting from qualitative information. User travel time showed good agreement between the proposed procedure and traditional web-based methods. Furthermore, the paper provides user delay costs functions accounting for traffic composition, trip purposes, vehicle operative costs, nonlinear volume–capacity relation, and average daily traffic. A significant aspect is the adaptability of this framework, as it is designed to be coupled with existing approaches. The method is demonstrated on a case study in Tuscany (Italy).

Contract bundling considerations in urban road project scheduling

AbstractRoad project scheduling and contract bundling are two separate concepts that profoundly influence project delivery consequences to key stakeholders. Therefore, agencies espouse initiatives for contract bundling (to reduce project costs) and project scheduling (to reduce user delay costs). Bundling combined with scheduling could potentially yield benefits to both the agency and urban road users. This paper investigates the overall benefits (to the two stakeholders) of optimal schedules with bundling considerations, compared to the optimal schedules for unbundled contracts. The agency's objective is to make scheduling‐with‐bundling decisions that minimize system‐wide travel time and project costs, and the users’ objective is to minimize their travel times in the network with work zones. The problem is solved using the non‐dominated sorting genetic algorithm. The numerical experiments suggest that with well‐designed bundling, optimal scheduling can significantly reduce not only the project cost but also the total system cost (project and travel delay).

Comparative Performance of Different Warm Mix Asphalt Technologies under the Influence of High Aircraft Tire Pressure and Temperature

Warm mix asphalt (WMA) technologies allow the production and placement of asphalt concrete materials at a lower temperature than the traditional hot mix asphalt (HMA). These materials simultaneously reduce the production fuel costs, increase the available hauling distance, lengthen the paving season, are eco-friendly, and ensure safer working conditions. Airport authorities can use such materials for construction applications to minimize the downtime and user-delay costs. However, the existing Federal Aviation Administration (FAA) construction specifications do not provide guidance on the implementation of such technologies, especially under the conditions created by aircraft with high tire pressure. To this end, the FAA National Airport Pavement and Materials Research Center (NAPMRC) conducted accelerated pavement tests as part of Test Cycle 1 (TC-1) to study the application potential of WMA (using chemical additive) on airport pavements. TC-1 results showed WMA performance was comparable to P-401 HMA performance in rutting. Test Cycle 2 (TC-2) study investigated the rutting performance of chemical, organic, and hybrid additive-based warm mixes alongside an FAA specification P-401 HMA counterpart. Four different test lanes were constructed accordingly in the outdoor area of NAPMRC, each encompassing three different test sections. Using the sixth-generation airport heavy vehicle simulator (HVS-A), sections on the north side of the test lanes were trafficked with 61.3 kips (272.7 kN) moving wheel load at a controlled temperature of 120°F (48.9°C). The chemical additive-based warm mix appeared to exhibit comparable performance to the HMA. A laboratory characterization effort also seemed to corroborate the rutting observations from traffic tests.

Sustainable Design of Diverging Diamond Interchange: Development of Warrants for Improving Operational Performance

Conventional diamond interchanges are facing ever-growing challenges related to traffic operations and safety risks due to increasing traffic volumes and worsening congestions. The agencies are well aware of the high socioeconomic (e.g., user delay cost, fuel cost, and high accident rates) and environmental losses (traffic emissions due to vehicles queuing) associated with the conventional interchange design. This paper provides insight into the different factors that affect the sustainability performance (operational and safety) of a conventional interchange through its redesign into the Diverging Diamond Interchange (DDI) with the increased left-turn demand. It also assesses the need to redesign an interchange to improve the efficiency. Two interchanges that have DDI designs were selected for investigations, and the required data were collected from the relevant agency. The average delay and the capacity were used as the Measures of Effectiveness (MOEs) for data analysis. Numerous factors, that affected these MOEs, were used to design an experiment. This experiment included different levels of volumes, geometric designs, and signal plans. The micro-simulation software (VISSIM 8.0) was employed to calibrate and validate the existing conditions through several steps, including signal optimization and driving behavior parameter optimization. The analysis of the results detected the key thresholds of switching from the conventional design to the innovative design under 90 different scenarios. Finally, the sustainability evaluation of DDI and Conventional Design Interchange was conducted based on their operation and safety performance comparison. The results and findings of this research will act as a guideline for decision-makers regarding when they should consider switching from the conventional interchange design to an innovative design.

Probabilistic Methodology to Quantify User Delay Costs for Urban Arterial Work Zones

AbstractThe total cost of road construction comprises direct costs paid by agencies and indirect costs paid by road users. In densely populated urban areas, work zone instigated user costs could ou...

Minimizing Cost of Highway Maintenance Considering the Impact of Vehicle Emissions using an Artificial Bee Colony Approach

The increasing traffic demand has reduced the efficiency of road networks and intensified the maintenance need for mobility and safety, increasing vehicle emissions, reducing air quality, and affecting climate change. To mitigate the negative impacts of work zone activities, a reliable method that can optimize spatio-temporal work zone activities is desirable. Previous studies have aimed to minimize the total cost, including maintenance, user delay, and accident costs, yet the associated environmental impact has been neglected. This study aims to optimize work zone activities using the artificial bee colony (ABC) algorithm, considering the cost of vehicle emissions in addition to the aforementioned costs for an environmentally sustainable optimization. MOtor Vehicle Emission Simulator (MOVES) is applied to calculate emission rates. The results show that the ABC algorithm is very efficient to search for the optimal solution that yields the minimum cost taking into account the well-being of the environment.

Optimal Timing for Lane(s) Addition to an Existing Highway: A Benefit–Cost Approach

The present study presents a comprehensive framework for optimal highway capacity expansion through lane(s) addition. The applicability of the proposed framework is demonstrated using data from a multi-lane urban arterial. In the proposed methodology, annualized widening costs (agency lane addition cost and work zone user delay cost) and excess user costs for do-nothing scenario (excess travel delay cost, excess vehicle operating cost and excess crash cost) were estimated for each analysis year within highway life cycle to estimate a range of traffic volumes for highway capacity expansion. Furthermore, a sensitivity analysis was conducted to evaluate the sensitivity of optimal time for highway capacity expansion to: (1) annual traffic growth rates (2) agency to user cost relative weights and (3) annual discount rate. Study results revealed that optimal highway capacity expansion time corresponds to an ADT ranging between approximately 34,430 and 37,600 vehicles per day for the case study traffic mix conditions. The sensitivity analysis results revealed that increase in agency to user cost relative weight and annual traffic growth rate would result in later and earlier optimal highway capacity expansion, respectively, while variations in annual discount rate have minimal impact on optimal highway capacity expansion timings. It is anticipated that the application of proposed framework can result in a sustainable decision by saving a huge amount of agency expenditures and excess user costs due to non-optimal decisions.

Network utility optimization-based joint user association and content placement in heterogeneous networks

The rapid growth of traffic demands has posed challenges and difficulties on both the radio access networks (RANs) and the backhaul links. While heterogeneous networks (HetNets) are expected to offer diverse radio access capabilities and improve the transmission performance of user equipments (UEs) significantly through integrating various RANs efficiently, the backhaul links may still experience challenges in offering quality of service (QoS) guaranteed services to UEs. To tackle these problems, caching technology, more specifically, caching user contents at the infrastructures of different RANs is proposed as an effective approach. In this paper, we consider the joint user association and cache content placement problem in cache-enabled HetNets. Stressing the tradeoff between user download delay and caching cost, we introduce the concept of utility function which characterizes the joint network performance as the weighted sum of user download delay and the caching cost and formulate the joint user association and cache content placement problem as a network utility optimization problem. As the formulated optimization problem is a nonlinear integer optimization problem which cannot be solved conveniently using traditional optimization tools, we transform the original optimization problem equivalently into three convex subproblems by applying Lagrange partial relaxation and McCormick envelopes, and then propose an iterative algorithm. Within each iteration, for a given set of Lagrange multipliers, the three subproblems are solved respectively by means of the modified Kuhn-Munkres (K-M) algorithm and the locally optimal solutions can be obtained, based on which the Lagrange multipliers can be updated through applying subgradient method. Simulation results demonstrate the effectiveness of the proposed algorithm.

User costs as one of main advantages of precast concrete application in highway construction

Road user cost primarily refer to the monetized components of road (re)construction impacts, such as the user delay costs, vehicle operating costs, crash costs and emission costs. Objective of this paper is to analyze and appraise the advantages and benefits of the innovative prefabrication approach in contrast to traditional cast-in-place construction method. The goal is to reduce these additional costs borne by motorists and the community at-large as a result of road construction activity to their minimum through application of the prefabrication. Assessing two basic possible approaches to highway infrastructure construction - casting the road pavements and structures either in place or precast off the site - it can be concluded that the initial capital investment costs do not vary much. Substantial differences can be recognized when comparing their life-cycle costs and an extent to which their construction process affects the public, environment and the local economy. Prefabrication of any structure component off-site offers major construction time and user cost savings in comparison with the traditional cast-in-place methods of construction. Precast prestressed road pavements’ technology and precasting bridges’ parts and elements offers dramatic increase in durability, while it also substantially decreases construction time and resulting user costs.

Decision Tree for Postflooding Roadway Operations

When a pavement is flooded, transportation agencies are faced with the decision to leave the road open or close it to traffic. On the one hand, agencies may want to keep the road open and prioritize connectivity if the road serves a critical economic purpose for a region. On the other hand, agencies may choose to close the road to prevent additional structural damage (which may incur significant repair costs) because of high water content in (or even saturation of) the subgrade. Nondestructive testing (NDT) tools such as the falling weight deflectometer (FWD) can be applied to assist decision makers by facilitating a more reliable evaluation of the structural condition of the pavement. Reliable decision making ought to incorporate inherent uncertainties in the process, including the structural state of the pavement after flooding, as well as the reliability of FWD testing and variability in costs. This paper presents a method that uses a Bayesian decision tree approach for highway emergency operations after flooding. Uncertainties in the structural state of the pavement after flooding, NDT, and costs are addressed with Monte Carlo simulations. A case study of a flooded roadway section in North Dakota demonstrated this approach: user delay costs caused by closure of the roadway were explicitly considered. The results of the decision tree analysis provide objective recommendations about opening or closing a road after flooding, as well as whether FWD testing of the flooded road should be conducted once the water recedes.

Reliability-based optimization of direct and indirect LCC of RC bridge elements under coupled fatigue-corrosion deterioration processes

An optimal bridge design should minimize the life cycle cost (LCC) of the structure without compromising its safety. Various cost components need to be evaluated when assessing the life cycle cost of a reinforced concrete bridge. When the structure is subjected to performance degradation due to aging, the probabilistic modeling of degradation is required. In this paper, the reliability-based design optimization RBDO is performed on the life cycle cost of the structure subject to deterioration processes of fatigue and corrosion. This paper advances the state of the art by: considering the coupled corrosion fatigue model in the design optimization and by developing a new approach to evaluate the user delay costs on a bridge, based on direct and indirect costs related to degradation and failure. Also, a sensitivity analysis of optimal costs and design variables is performed. The improved life cycle cost analysis presented herein can be applied to select the optimal design of reinforced concrete bridge elements, by minimizing both agency and bridge user costs, while providing the required safety along the structure lifetime, taking into account the most severe degradation processes.

A new method for evaluating the sustainability of bridges

Civil infrastructure projects such as bridges can have a major impact on many of the issues relevant to sustainability and it is therefore important that civil and structural engineers have methods at their disposal that will help them deliver sustainable designs. This paper describes a new model for appraising the sustainability of bridges. The indictors used to assess sustainability are climate change, resource use, waste, biodiversity and heritage, noise, dust, vibration, aesthetics, employment and businesses, construction costs, maintenance costs and user delay costs. The paper describes the aim of each indicator and provides details of the methods of measurement. The paper also presents the results of a case study on the appraisal of three alternative designs of an over-bridge for a dual two-lane motorway to discover which option is the most sustainable. Details of the key input parameters are provided. The way in which individual impacts are combined to produce an overall sustainability score for a given structure is highlighted. The paper concludes with a discussion on interpreting the results and ways of further improving the sustainability of the selected design.

Economic Analysis of Buried Corrugated Steel Culverts Considering Deterioration

The characteristics of the corrugated steel culvert and the deterioration of the structure are analyzed. The Life Cycle Cost (LCC) approach is put forward to analysis the initial, maintenance and recycling cost of the different material culverts. The user delay costs are added to the typical LCC values considering the deterioration and the failure of structures. The analysis and the economic comparison results show that the total LCC values at the failure emergency situation is much larger than the situation when the deterioration is considered initiatively. Such economic analysis can help the project decision makers better understand the risks associated with deterioration and failure. The inspection and maintenance schedule should be formulated considering the culvert size, the environment in which the culvert is placed, and the characteristics of the soil and the backfill.

Elements of pavement management system: case study

This paper presents the elements of a Pavement Management System with a particular focus on the initial effort to create a comprehensive data archive and its further application in four different maintenance strategies. Pavement performance indicators including longitudinal and transverse cracking as well as roughness were investigated with respect to numerous distinct factors which can be grouped into three categories, i.e. climatic, pavement structure, and traffic-related. High-quality climatic data was obtained from the national weather stations in Connecticut. Maintenance and construction data was used to determine the pavement age and structure amongst several other factors. Traffic data was acquired from the state records and accumulated traffic loading was estimated for all segments based on their age. High definition pavement images collected by the Automatic Road Analyzer vehicle in 2010 were used to quantify the longitudinal and transverse cracking with respect to their location within the pavement surface. Elements of the Pavement Management System with stochastic elements were created from this data and analyzed in order to demonstrate the budget implications under four different management scenarios. Scenarios varied by the trigger values of the Pavement Condition Index for considered maintenance treatments. The 20-year projection analysis clearly showed the benefit of repairing pavements that are still in a good condition even without considering related user-delay costs and/or vehicle-operation costs which would only heighten the differences between scenarios.

Bridge user cost estimation – a synthesis of existing methods and addressing the issues of multiple counting, workzones and traffic capacity limitation

Efforts to incorporate the concerns of bridge users in bridge investment evaluation are often stymied by lack of a comprehensive framework for assessing different user costs. There is a need to synthesise and update existing user cost estimation techniques so that the incorporation of user costs in bridge investment evaluation can be more consistent and streamlined. Secondly, a bridge detour may occur for more than one reason, thus there is a danger of multiple counting that could cause overestimation of user costs. Thirdly, user costs during bridge workzones have rarely been considered in the literature. To address these issues, this article presents a framework for comprehensive estimation of bridge user costs, an approach to address the multiple-counting problem, and a methodology for bridge workzone user cost estimation. Furthermore, the article develops a method to estimate bridge user delay cost due to traffic capacity limitation. The methodologies are demonstrated using a case study.

Full Closure or Partial Closure? Evaluation of Construction Plans for the I-5 Closure in Downtown Sacramento

Three alternative construction plans with full highway closures and limited capacity closures (partial closures) are evaluated for a large-scale freeway reconstruction project in the Sacramento metropolitan area. By using a dynamic network analysis tool, the potential impact resulting from different construction plans is estimated and analyzed measured by changes in total demand, travel delays, vehicle miles/hours traveled (VMT/VHT), fuel consumptions, and emissions. The results show that, for this Interstate 5 closure, if only user delay costs are considered, the actual full closure plan is the best. It produces considerably less total system travel delay than the two partial closure plans although it closed more lanes. This plan, however, may induce more VMT than the other two. In fact, the other two partial closure plans produce slightly fewer emissions and consume slightly less fuel. The outcome of which plan comes out on top crucially depends on two other factors, besides the chosen objective: the amount of demand reduction a plan induces and the availability of alternative routes to divert traffic away from the work zone area. Developing efficient demand management measures will be the key to improving the network performance and to reduce the emissions. Moreover, when data are available, construction costs and emissions produced by construction activities should also be included in the evaluations, in addition to the user costs considered in this study.

Life-Cycle Cost Assessment of Maintenance Strategies for RC Structures in Chloride Environments

Corrosion of the reinforcing steel can cause cover cracking and eventual spalling of reinforced concrete (RC) surfaces, resulting in costly and disruptive repairs. The present paper will compare the effect of maintenance and repair strategies on the timing, extent, and cost of remediation actions over the service life of a RC structure in a chloride environment. The paper presents a probabilistic reliability analysis, which is used to predict the likelihood and extent of corrosion-induced cracking to RC structures. A spatial time-dependent reliability model has been developed where concrete properties, concrete cover, and the surface chloride concentrations are treated as random fields. This allows for the calculation of the probability that a given extent of damage will occur for any time period. Maintenance strategies and repair efficiencies are incorporated in a Monte-Carlo event-based simulation analysis, allowing a comparison in terms of cost and number of repairs over the service life of a RC structure. Thus, the expected timing and extent of repairs can be predicted for various design parameters, inspection intervals, repair thresholds, maintenance strategies, and efficiency of repairs. Results are presented for a RC bridge deck subject to a marine environment. The life-cycle cost (LCC) analysis considers repair and user delay costs. User delay costs can be up to ten times higher than the cost of repair itself. The statistical variability of predicted LCCs can be large, with coefficients of variation exceeding one. DOI: 10.1061/(ASCE)BE.1943-5592.0000248. © 2012 American Society of Civil Engineers.

Multifaceted public outreach and cost–benefit analysis for its effectiveness validation

A heavily trafficked 4.5km highway stretch on Interstate 15 east of Los Angeles was rebuilt using two extended closures, each spanning nine days with 24/7 operations. Before and during the closures, a multifaceted, extensive, dynamic public outreach programme was implemented to gain public support for the project and to minimize inconvenience to the public. That outreach programme is described, its overall effectiveness in terms of total net benefit and traffic inconvenience during lane closures is assessed, and changes in public perception of the accelerated construction strategy resulting from the outreach programme is examined. Pre‐ and post‐construction surveys performed using the project website mirrored the findings of the traffic measurement study, indicating that the outreach programme effectively reduced traffic demand. The results of two web‐based surveys with a combined total of approximately 400 respondents indicated a dramatic change in public perception of the accelerated construction strategy. The survey results showed that strong initial objection to the accelerated project eventually became supportive of future, accelerated projects. The cost–benefit analysis showed that the additional cost of the outreach programme was outweighed by the savings achieved from reduced road user delay costs.

Alternative valuation of highway user delay costs

Improved highway networks result in net benefits to society, of which the reduction in travel time is one of the most important. Similarly, the delay in travel due to construction and maintenance operations represents a real cost to users. Assignment of the value of time in the cases of both benefit and cost involves judgment, since individuals value time differently and adjust for travel time changes in various ways. Values based on wage rates traditionally have been used because they are convenient, but alternative approaches based on leisure or survival are worthy of investigation. A full life-cycle cost assessment of a project requires an evaluation of future savings in travel time projected over a project’s lifetime, as well as delay costs associated with construction and subsequent maintenance operations. Due to its economic as well as social complexity, alternative measures of user travel time valuation and its network effects need to be considered.