Impact of environmental assessment and budgetary restrictions in pavement maintenance decisions: Application to an urban network

Road agencies are facing the challenges of aging pavements, deteriorating networks, and insufficient maintenance budgets. This study addresses two limitations in the current state of practice in pavement management. First, because the evaluation of maintenance strategies has traditionally focused on economic and technical aspects, it neglects the environmental impact of maintenance decisions. Second, current management systems often provide a unique, optimised pavement maintenance strategy based on a specific objective(s) and constraint(s). The main objective of the study is to analyse the effect of including environmental aspects and funding availability in the design of maintenance strategies. To achieve this objective, the study followed a three-step methodology. First, this study reviews existing practices on pavement maintenance and the criteria considered to trigger the application of maintenance treatments and their effects on pavement condition. Then, maintenance strategies are optimised considering three levels of budgetary capacity and a sustainable evaluation which incorporates technical, economic, and environmental aspects over the pavement lifecycle. Finally, a case study dealing with an urban pavement network in Chile is analysed. Results obtained from this case study show that an increment of 2% in maintenance budget allows to account for more sustainable maintenance decisions, such as cold in-place recycling and full-depth slab repair, whose greenhouse gas emissions are lower than other alternatives. Results also show that functional asphalt overlay and microsurfacing are more recommended in flexible pavements when budgetary restrictions are low, whereas recommended treatments for rigid pavements exhibit small variability with budgetary restrictions.     

Evaluating the effects of climate change on road maintenance intervention strategies and Life-Cycle Costs

Climate change has the potential to impact long-term road pavement performance. Consequently, to maintain pavements within the same ranges of serviceability as before, current pavement maintenance strategies need to be re-assessed and, if necessary, changed. Changes in maintenance may lead to different agency costs and user costs as a consequence. This paper commences by defining an assessment procedure, showing how maintenance intervention strategies and Life-Cycle Costs (LCC) may be affected by future climate. A typical Virginia flexible pavement structure and anticipated climate change was used as an example. This example is believed to be representative for a great number of localities in the United States. A method using historical climatic data and climate change projections to predict pavement performance using Mechanistic-Empirical Pavement Design Guide (MEPDG) under current or future climate was introduced. Based on pavement performance prediction, maintenance interventions were planned and optimized. The maintenance effects of three treatments (thin overlay, thin overlay with an intermediate layer, and mill & fill) were considered. A Life-Cycle Cost analysis is reported that used binary non-linear programming to minimize the costs (either agency costs or total costs) by optimizing intervention strategies in terms of type and application time. By these means, the differences in maintenance planning and LCC under current and future climate can be derived. It was found, that for this simplified case study, pavement maintenance and LCC may be affected by climate change Optimized maintenance may improve resilience to climate change in terms of intervention strategy and LCC, compared to responsive maintenance.     

Comparative life-cycle assessment of conventional (double lane) and non-conventional (turbo and flower) roundabout intersections

This research studied and compared different construction techniques for the road subgrade, embankment and pavement of different types of roundabout intersections in order to assess their environmental sustainability. A Life Cycle Assessment (LCA) was carried out on double lane, turbo- and flower roundabouts.We considered virgin materials and reclaimed asphalt pavement (RAP) for the pavement construction. Also the environmental effects due to in situ lime stabilization of fine-grained soils were assessed in order to reduce the use of virgin material in road subgrades.The use of reclaimed asphalt pavement (RAP) can lead to a significant reduction in pollutant emissions and energy consumption (especially due to the lesser material transport) – though with a slightly different impact according to the different percentages employed – compared to the pavements constructed with virgin materials. The same consideration can be made for fine soils with in situ lime stabilization: on the one hand, the technique allows to improve significantly the mechanical properties of soils which would be otherwise dumped and, on the other, to provide considerable environmental benefits. The life cycle assessment of the pavement was carried out with the help of the PaLATE software (by comparing different maintenance scenarios) while emissions and energy consumption in the use phase at intersections were evaluated by means of closed-form models (to estimate vehicle delays and speeds of vehicles) and the COPERT software.Finally, the generalized costs covered in the whole life cycle of roundabouts (i.e. sum of construction, maintenance and environmental costs) were assessed and associated to the different construction options.     

Quantifying sustainable strategies for the construction of highway pavements in Illinois

The environmental and economic burdens of various pavement construction strategies are evaluated in this study. A partial life-cycle approach was used to determine the environmental and economic benefits of asphalt concrete and Portland concrete mix designs as well as pavement-related pay items. Approximately 920 designs were assessed to determine the upstream energy consumption and global warming potential (GWP) of producing these mixes. In general, it was found that transportation hauling distances as well as asphalt binder type and production imposed the greatest variability on the environmental and economic costs of the mixes. In many cases, these variabilities were seen to reduce some of the benefits from using increased recycled content. A similar analysis was performed for pay items where it was found that the contribution of environmental and economic impacts to a project followed a trend with upper pavement layers having the greatest impact, followed by subsequently lower layers, and finally earth exaction and preparation. A cost effectiveness (CE) analysis was then conducted for 18 sustainable strategies, the majority of which had, on average, cost savings as well as environmental savings for both energy and GWP at the mix design level. Overall, this study systematically used common reference units (i.e., mix designs and pay items) from the industry to assess general trends, inconsistencies, and implications from using sustainable strategies in pavement construction.     

Life cycle assessment of heated apron pavement system operations

Heated pavement systems (HPS) offer an attractive alternative to the cumbersome process of removing ice and snow from airport pavements using traditional snow removal systems. Although snow and ice removing efficiency and economic benefits of HPS have been assessed by previous studies, their environmental impact is not well known. Airport facilities offering public or private services need to evaluate the energy consumption and global warming potential of different types of snow and ice removal systems. Energy usage and emissions from the operations of hydronic heated pavement system using geothermal energy (HHPS-G), hydronic HPS using natural gas furnace (HHPS-NG), electrically heated pavement system (EHPS), and traditional snow and ice removal system (TSRS) are estimated and compared in this study using a hybrid life cycle assessment (LCA). Based on the system models assessed in this study, HPS application in the apron area seems to be a viable option from an energy or environmental perspective to achieve ice/snow free pavement surfaces without using mechanical or chemical methods. TSRS methods typically require more energy and they produce more greenhouse gas (GHG) emissions compared to HPS during the operation phase, under the conditions and assumptions considered in this study. Also, HPS operations require less energy and have less GHG emissions during a snow event with a smaller snowfall rate and a larger snow duration.     

Towards the Incorporation of Environmental Impacts into Pavement Management Systems

Environmental nuisances (such as greenhouse gases and noise) may be generated during the use phase of the pavement life cycle, with these known to significantly affect the environment. However, no attempt has yet been made to gather information concerning the processes involved in the generation of environmental impacts, and to evaluate them. To address this issue, this paper reviews the knowledge base and relevant methods relating to environmental impact assessment and pavement management. It then presents a conceptual model, integrating impact pathway approach and life cycle cost analysis principles and providing a comprehensive framework for quantification and incorporation of environmental impacts into pavement management. This study shows that pavement management influences environmental impacts occurring during the use phase of the pavement life cycle. It establishes causal links between pavement management and nuisance generation, between nuisances and their impact on receptors, and finally between these impacts and their costs. This study also suggests that incorporating environmental impacts into pavement management systems is feasible and describes how existing and future methodologies and tools may be integrated to support this incorporation. Finally, this study underlines that the inaccuracy of current knowledge and data limits the scope of this conceptual model to network-level decisions.     

沥青路面冷再生沥青混合料配合比设计研究

冷再生沥青混合料施工技术是一种节能环保的公路路面修复技术,不但可以有效减少石料、沥青、水泥的需求量,降低工程成本,减少了资源浪费,并且与热再生技术相比可以有效降低CO2排放量。配合比设计是影响冷再生沥青混合料质量的关键因素,本文以某公路沥青路面修复工程为例,对沥青路面冷再生沥青混合料配合比进行研究,以加强冷再生沥青混合料质量控制。     

广西天然碎石土路面低造价硬化技术研究

农村公路中大量存在的碎石路面由于缺少胶结材料，路面强度低、结构松散，极大的影响着农村公路的通行能力。文章以广西农村公路砂石路面为依托进行了低造价改造技术的试验研究。通过现场取样和室内、外试验结果分析，提出了适宜于农场公路碎石土路面改造的低造价硬化技术方案     

机场刚性道面PCN计算方法的对比分析研究

文章对我国机场刚性道面的两种不同的PCN计算方法进行对比研究,分析了同等道面情况下二者之间的差异,并对二者的主要影响因素进行了敏感性分析。研究结果表明：当量单轮荷载计算方法较设计飞机法计算结果偏大,主要受道面厚度及地基强度影响;设计飞机计算方法综合考虑道面自身及航空交通量双方面因素,计算结果更加接近实际情况,但因根据评价机型的选取不同,所得结果并不唯一。     

The effect of time on acoustic durability of low noise pavements – The case studies in Poland

The tyre/road noise depends on type and speed of vehicles and on the characteristics of road pavement. Vehicle traffic load and weather conditions lead to significant changes in the characteristics of the materials used to build the wearing course. This applies especially to road pavements with the increased void contents. Clogging of the pores, changes in the characteristics of the binder and the damage to the wearing course influence changes in the acoustic properties of the road pavement over time. The article presents the results of the studies on noise level carried out in 2011 and 2014 by the Statistical Pass-By method (SPB) on porous asphalt concrete (PAC), very thin asphalt concrete (VTAC) and stone mastic asphalt (SMA). The wearing courses with the increased void contents immediately after building constitute a very advantageous solution compared with traditional road pavements (dense asphalt concrete, stone mastic asphalt). However, the unfavourable location of the road with porous wearing course, lack of systematic cleaning of porous layers or inappropriate maintenance methods in winter lead to the loss of the acoustic durability of low-noise pavements within a few years of their exploitation.     

Joint optimization of freight facility location and pavement infrastructure rehabilitation under network traffic equilibrium

Establishment of industry facilities often induces heavy vehicle traffic that exacerbates congestion and pavement deterioration in the neighboring highway network. While planning facility locations and land use developments, it is important to take into account the routing of freight vehicles, the impact on public traffic, as well as the planning of pavement rehabilitation. This paper presents an integrated facility location model that simultaneously considers traffic routing under congestion and pavement rehabilitation under deterioration. The objective is to minimize the total cost due to facility investment, transportation cost including traffic delay, and pavement life-cycle costs. Building upon analytical results on optimal pavement rehabilitation, the problem is formulated into a bi-level mixed-integer non-linear program (MINLP), with facility location, freight shipment routing and pavement rehabilitation decisions in the upper level and traffic equilibrium in the lower level. This problem is then reformulated into an equivalent single-level MINLP based on Karush–Kuhn–Tucker (KKT) conditions and approximation by piece-wise linear functions. Numerical experiments on hypothetical and empirical network examples are conducted to show performance of the proposed algorithm and to draw managerial insights.     

The importance of the use phase on the LCA of environmentally friendly solutions for asphalt road pavements

In order to assess sustainability of products and processes, different methodologies have been developed and used in the last years. In the road pavement construction area, most methodologies used for Life Cycle Assessment (LCA) are essentially focused in the construction phase. The present paper analyses the importance of the use phase of a road in the LCA of different paving alternatives, namely by evaluating energy consumption and gaseous emissions throughout the road pavement’s life. Therefore, a new LCA methodology for road pavements was developed, and the results of its application to a case study involving the construction of alternative pavement structures are discussed. The study intends to assess the influence of using more sustainable paving construction alternatives (asphalt recycling vs. conventional asphalt mixtures), and/or different surface course materials (which have a higher influence on the rolling resistance and, therefore, affect the performance during the use phase). The LCA results obtained for this case study showed that the reductions in energy consumption and gaseous emissions obtained during the use phase, for pavement alternatives with a lower rolling resistance surface course, are higher than the total amount of energy consumption and gas emissions produced during construction. It is therefore clear that some improvements in the characteristics of the surface course may have an effect over the road use phase that will rapidly balance the initial costs and gas emissions of those interventions. The LCA results obtained also showed that the sustainability of pavement construction may also be improved using recycled asphalt mixtures.     

Planning strategies for promoting environmentally suitable pedestrian pavements in cities

This paper examines the relevance of incorporating comprehensive life-cycle environmental data into the design and management of pedestrian pavements to minimize the impact on the built environment. The overall primary energy demand and global warming potential of concrete, asphalt and granite sidewalks are assessed. A design with a long functional lifetime reduces its overall primary energy demand and global warming potential due to lower maintenance and repair requirements. However, long-lived construction solutions do not ensure a lower life-cycle primary energy demand and global warming potential than for shorter-lived designs; these values depend on the environmental suitability of the materials chosen for paving. Asphalt sidewalks reduce long-term global warming potential under exposure conditions where the functional lifetime of the pavements is less than 15 years. In places where it is known that a concrete sidewalk can have a life of at least 40 years, a concrete sidewalk is the best for minimizing both long-term primary energy demand and global warming potential. Granite sidewalks are the largest energy consumers and greenhouse gas contributors.     

Life cycle assessment of bituminous pavements produced at various temperatures in the Belgium context

Bituminous mixture is the premier material for road construction in Belgium. Innovative technologies to improve energy efficiency of pavement constructions are necessary. Warm mix asphalt may provide significant energy savings to the asphalt industry, but the environmental impact of the total life cycle has to be investigated. The use of additives may counteract the reduced environmental impact due to energy savings. This paper presents the results of an environmental impact assessment of four wearing course test sections. Using life cycle assessment, hot mix asphalt is compared to a cold asphalt mix with emulsion and warm mix asphalt with two types of additives: a synthetic zeolite and an organic Fischer–Tropsch wax. Neither hot nor warm mix asphalt could be preferred based on the results of this study, because the additive has a major influence on the environmental results. It was seen that the production of bitumen, the transport and energy in order to generate heat mainly contribute to the total environmental impact. The results from the sensitivity analyses show that the total environmental impact of the life of the pavement can vary significantly based on the choice of the specific data source and service life.     

A comparative study of the emissions by road maintenance works and the disrupted traffic using life cycle assessment and micro-simulation

Life cycle assessment is being accepted by the road industry to measure such key environmental impacts as the energy consumption and carbon footprint of its materials and laying processes. Previous life cycle studies have indicated that the traffic vehicles account for the majority of fuel consumption and emissions from a road. Contractors and road agencies are looking for road maintenance works that have the least overall environmental impact considering both the roadwork itself and the disrupted traffic. We review life cycle assessment studies and describe the development of a model for pavement construction and maintenance, detailing the methodology and data sources. The model is applied to an asphalt pavement rehabilitation project in the UK, and the micro-simulation program VISSIM is used to model the traffic on that road section. The simulation results are fed into a traffic emissions model and emissions from the roadwork and the traffic are compared. The additional fuel consumption and emissions by the traffic during the roadwork are significant. This indicates that traffic management at road maintenance projects should be included in the life cycle assessment analysis of such work.     

Traffic noise abatement: How different pavements, vehicle speeds and traffic densities affect annoyance levels

In this paper, annoyance ratings from traffic noise recorded on cobblestones, dense asphalt, and open asphalt rubber pavements are assessed with regard to car speeds and traffic densities. It was found that cobblestones pavements are the most annoying; also while open asphalt rubber pavement imposes less annoyance than dense asphalt it is not significantly different. Higher car speeds always lead to greater annoyance, as does higher traffic densities. LAeq and LAmax correlate well with annoyance, but loudness is the best predictor. Roughness and sharpness exhibit inconsistent interactions.     

Life cycle assessment of pavement: Methodology and case study

A life cycle assessment model is built to estimate the environmental implications of pavements using material, distribution, construction, congestion, usage, and end of life modules. A case study of three overlay systems, Portland cement concrete overlay, hot mixture asphalt overlay, and crack, seat, and overlay, is presented. The case leads to the following conclusions. It is reasonable to expect less environmental burdens from the Portland cement concrete and crack, seat, and overlay options as opposed to hot mixture asphalt while although the results have a high degree uncertainties. The material, congestion, and particularly usage modules contribute most to energy consumption and air pollutant. Traffic related energy consumption and greenhouse gases are sensitive to traffic growth and fuel economy improvement. Uncertainties exist in the usage module, especially for the pavement structure effect.     

公路沥青复合料冷再生路面的结构设计分析研究

公路路面冷再生翻新技术充分利用旧路破拆材料,处理和避免了旧路破拆垃圾,也一定程度节省了新料的投入,符合节能环保公路建设理念。但旧料冷再生利用,必须以新路面基本技术性能得到充分保证为前提。本文基于JTGD50-2017规范,参考国内公路沥青路面的毁损病害多发状态与冷再生复合料的基本性能功效,对公路沥青复合料冷再生新路面开展结构设计分析研究,探讨了三种路面厚度设计方案,提出了一个新的沥青复合料冷再生新路面的结构设计方法。     

公路面层三性磨耗机理与建议

文章结合路面磨耗力学的规律,介绍混凝土路面类型及磨耗形式,分析了公路面层剪切性磨耗、剥落性磨耗、液压性磨耗三性磨耗机理,并为公路面层避免或减少磨耗提出相关的建议。     

Investigating effects of asphalt pavement conditions on traffic accidents in Tennessee based on the pavement management system (PMS)

Pavement maintenance is essential for ensuring good riding quality and avoiding traffic congestion, air pollution, and accidents. Improving road safety is one of the most important objectives for pavement management systems. This study utilized the Tennessee Pavement Management System (PMS) and Accident History Database (AHD) to investigate the relationship between accident frequency and pavement distress variables. Focusing on four urban interstates with asphalt pavements, divided median types, and 55 mph speed limits, 21 Negative Binomial Regression models were developed for predicting various types of traffic accident frequencies based on different pavement condition variables, including rut depth (RD), International Roughness Index (IRI), and Present Serviceability Index (PSI). The modeling results indicated that the RD models did not perform well, except for predicting accidents at night and accidents under rain weather conditions; whereas, IRI and PSI were always significant prediction variables in all types of accident models. Comparing the models goodness‐of‐fit results, it was found that the PSI models had a better performance in crash frequency prediction than the RD models and IRI models. This study suggests that the PSI accident prediction models should be considered as a comprehensive approach to integrate the highway safety factors into the pavement management system. Copyright © 2010 John Wiley & Sons, Ltd.