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Challenges associated with ensuring the accuracy and reliability of cost estimation of highway construction bid items are of significant interest to state highway transportation agencies. Even with the existing research undertaken on the subject, the problem of inaccurate estimation of highway bid items still exists. This paper aims to assess the accuracy of the cost estimation methods employed in the selected studies to provide insights into how well they perform empirically. Additionally, this research seeks to identify, synthesize and assess the impact of the factors affecting highway unit prices because they affect the total cost of highway construction costs.

This paper systematically searched, selected and reviewed 105 papers from Scopus, Google Scholar, American Society of Civil Engineers (ASCE), Transportation Research Board (TRB) and Science Direct (SD) on conceptual cost estimation of highway bid items. This study used content and nonparametric statistical analyses to determine research trends, identify, categorize the factors influencing highway unit prices and assess the combined performance of conceptual cost prediction models.

Findings from the trend analysis showed that between 1983 and 2019 North America, Asia, Europe and the Middle East contributed the most to improving highway cost estimation research. Aggregating the quantitative results and weighting the findings using each study's sample size revealed that the average error between the actual and the estimated project costs of Monte-Carlo simulation models (5.49%) performed better compared to the Bayesian model (5.95%), support vector machines (6.03%), case-based reasoning (11.69%), artificial neural networks (12.62%) and regression models (13.96%). This paper identified 41 factors and was grouped into three categories, namely: (1) factors relating to project characteristics; (2) organizational factors and (3) estimate factors based on the common classification used in the selected papers. The mean ranking analysis showed that most of the selected papers used project-specific factors more when estimating highway construction bid items than the other factors.

This paper contributes to the body of knowledge by analyzing and comparing the performance of highway cost estimation models, identifying and categorizing a comprehensive list of cost drivers to stimulate future studies in improving highway construction cost estimates.

Various approaches have emerged to assist practitioners in making more informed decisions in highway construction projects. However, industry practitioners are still using subjective ways to make decisions. Also, researchers have developed tools and techniques with similar objectives. Lack of information on what has been developed might lead to those issues. Therefore, this paper aims to review trends of evolution, pinpoint strengths and gaps in the literature and identifies potential future directions for decision-making research in highway construction projects.

A systematic review was conducted on published articles on decision-making in highway construction projects using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) technique.

The analysis of 101 articles revealed that existing decision-making research in highway construction projects targets improvements in four areas: feasibility, conceptual, detailed scope and detailed design. The four areas consist of sixteen subthemes that are detailed in this study. In addition, most research involved developing decision support tools and systems as well as decision-making models, techniques and frameworks. Lastly, several research areas have emerged, such as adding more decision criteria including those with uncertainties, expanding existing decision-making models into decision support systems, benchmarking decision criteria between different sample populations and exploring inter-and intra-relationships between decision criteria.

This paper provides an overview of existing research on decision-making in highway construction projects. Also, it reveals research gaps in the body of knowledge to point out directions for future research. Finally, industry practitioners can use the findings to develop strategies for effective decision-making processes.

According to the Federal Highway Administration (FHWA), and based on its professional judgment, it typically takes from 9 to 19 years to plan, gain approval for, and construct a new, major federally funded highway project that has significant environmental impacts. However, these projects constitute only 3 percent of all federally funded projects, according to FHWA. Officials in federal and state agencies and other knowledgeable organizations indicate that delivering larger, more complex or controversial projects may take longer to complete than is typical for most highway projects. In addition to needing more time because of their size and complexity, they often take longer to complete because they must comply with more federal and state requirements and because of the public interest that they may generate. Federal and state agencies have undertaken several initiatives to improve completion times for highway construction projects. Most of these initiatives address opportunities for reducing the time required to obtain environmental approvals.

Evaluating the implementation of environmental management plans (EMPs) in highway construction projects is essential to avoid climate change. Public evaluations can help ensure that the EMP is implemented correctly and efficiently. To allow public evaluation of EMP implementations, this study aims to investigate performance indicators (PIs) for assessing EMP implementation in highway construction projects. To that end, the study objectives are to compare the critical PIs between environment auditors (EAs) and environment officers (EOs) and among the main project stakeholders (i.e. clients, contractors and consultants), create components for the critical PIs and assess the efficiency of the components.

The paper identified 39 PIs from interviews with environmental professionals and a systematic literature review. Then a questionnaire survey was developed based on the PIs and sent to EAs and EOs. The data were analyzed via mean score ranking, normalization, agreement analysis, factor analysis and fuzzy synthetic evaluation (FSE).

The analyses revealed 21 critical PIs for assessing EMP implementation in highway construction projects. Also, the critical PIs can be grouped into four components: ecological, pollution, public safety and ecological. Finally, the overall importance of the critical PIs from the FSE is between important and very important.

To the best of the authors’ knowledge, this paper is the first-of-its-kind study on the critical PIs for assessing EMP implementation in highway construction projects.

The purpose of this study is to determine whether there is a correlation between mobilization costs and project schedule performance of highway projects. In addition to this, the study will also determine if the mobilization costs are helping small or large highway projects in terms of improving the schedule performance.

The data of 206 highway projects were collected from the Department of Transportation of two states with the help of questionnaire survey. The cost, schedule and mobilization costs data were collected. The performance metrics related to construction schedule growth and construction intensity were developed in order to test the research hypotheses: mobilization costs will increase the schedule performance of highway projects. The data were also divided into two groups based on project cost and analyzed to check whether the mobilization costs impact the schedule performance of these highway projects. Spearman's correlation test was conducted to determine the correlation between dependent and independent variables. In addition, a Mann–Whitney test was conducted to determine the difference in medians of construction schedule growth and the construction intensity of these two groups of projects.

One major study finding was that there was no strong linear correlation between the mobilization cost percentage and the construction schedule growth and construction intensity of highway projects. However, the study found the projects that have 9% or more mobilization costs had significantly better schedule growth compared to the projects that have less than 9% mobilization costs. When data were analyzed based on the project size, it was found that this pattern was seen only in large projects costing equal to or more than $5 million.

This study's findings have very crucial practical implications to state DOTs contract engineers. This study shows that the highway contract engineers need to provide the right amount of mobilization costs to complete their projects on and before schedule. If the correct amount of mobilization costs is not provided to the contractors, the impact of these mobilization costs on reducing the schedule growth will be negligible. The findings of this study will assist public agency decision makers to complete their projects on or before time by including the mobilization costs provision in the contract. The state DOTs can improve their schedule performance by providing enough financial help to the contractors so that they can improve their cash flows and complete projects successfully within the given timeframe.

This paper contributes to the existing body of knowledge by validating the impact of mobilization costs on the schedule performance of highway projects. There has been no empirical study conducted prior to this to identify the role of mobilization costs on reducing the schedule growth of highway projects.

This study aims at identifying the main causes of change orders in highway construction projects, determining the factors that affect rework in highway construction projects, examining the relationship between change orders and rework and at developing a predictive model that will determine the impact of change orders on rework in highway construction projects in Palestine.

A questionnaire survey was used to identify the main change order causes and rework causes from the perspectives of contractors and consultants. The questionnaire contained 16 causes of change orders and 19 causes of rework which had been identified from the literature reviewed. The study also identifies the impact of change orders on rework based on data comprising 22 highway construction projects implemented in Palestine. Both descriptive and inferential statistics were used in analyzing the data.

The study concluded that the five most common causes of change orders can be identified as: change of project scope by owner (additional – enhancement), lack of coordination between construction parties; owner’s financial difficulties, change in materials, and errors and omissions in design. The study has also established that among the various factors that causes rework, non-conformance with specification requirements, scope changes, late design changes, lack of labor experience, lack of labor skills and improper subcontractor selection top the list. Using regression analysis, the results reveal a significant relationship between change orders and rework cost in highway construction projects in Palestine.

By ranking the various change orders causes and rework causes from the perspectives of consultants and contractors, the study provides a fresh perspective on an old chronic problem in the construction sector. This study has provided evidence on the most significant change orders causes and rework causes in the Palestinian highway construction, as well as the impact of change orders or rework on constructions sites. Finally, although this study is specific to the country of Palestine, its results can be applicable to other developing countries facing similar problems in their public construction sectors.

The results address the common causes of change orders and reworks in highway construction projects in Palestine. The results also address the relation between change orders and rework cost based on data collected from highway construction projects implemented in the West Bank in Palestine. This study is the first study conducted in the West Bank in Palestine to identify the change orders and reworks causes in highway construction projects.

Public-private partnership (PPP) highway projects in India are undertaken at both state and national levels, such that differences exist in how the procuring authorities manage project risk during the development and construction phase under different institutional frameworks. This study assesses the performance implication of the different administrative positionings of the procuring authority.

A data set of 516 PPP highway projects implemented in India formed the basis of this study. Means comparison, ordinary least squares (OLS) regression and seemingly unrelated regression were used to assess the impact of procuring authority on schedule performance.

The findings suggest that the state and the national highway projects were no different in achieving financial closure. However, the administrative positioning of the procuring authorities had a significant impact on other schedule performance variables. The construction of the state highway projects started quickly after the financial closure compared to the national highway projects. Moreover, the state highway projects were not only planned to be implemented at a faster rate but they were actually implemented at a faster rate and had a lower time overrun.

Procuring authorities under the state governments, being closer to the project, are better placed to manage project risk than those under the national government.

The administrative distance of the procuring authority from the PPP project and its implication on performance has never been studied.

The purpose of this paper is to develop models to forecast final budget and duration of a highway construction project during construction stage.

Highway construction project data are collected and analyzed to find out factors affecting project final budget and duration before developing the forecasting models, research for which is based on the principle of Artificial Neural Network (ANN). The forecasting results obtained from the proposed method are compared with those obtained from the current method based on earned value.

Factors affecting final budget and duration are presented. The forecasting results obtained from the proposed method based on ANN application are more accurate and stable than those obtained from the current method based on earned value.

Factors affecting final budget and duration may differ if applied in other countries, since the project data were collected in the Kingdom of Thailand. The forecasting models, therefore, must be reconsidered for better outcomes.

The study presents a useful tool for the highway construction project manager to predict project final budget and duration. The results can potentially provide early warning of over‐budget and schedule delay.

The ANN models to forecast final budget and duration of highway construction projects during the construction stage, developed by using project data reflecting continual and seasonal cycle data, can provide better predicting results.

This study aims to analyze the interaction and key factors within the network of factors influencing the success of green highway projects.

Through literature review and interviews with experienced project managers, this study identified 33 influencing factors from the perspectives of stakeholders and life cycle. The interaction between these influencing factors was determined by surveying different experts, most of whom have participated in green highway projects in China. Then, social network analysis (SNA) was used to explore the impact and control ability of different factors.

According to the prioritization of these factors, the results showed that some key factors were identified, especially incremental cost, lack of standards and regulations, development of innovative technologies and materials, public awareness and environmental protection behavior. Finally, some meaningful suggestions were put forward for different influencing factors of green highway projects.

While the key influencing factors of the green highway projects have been identified by considering the interrelationships between different factors, the specific influencing paths and levels of different factors are not analyzed, more studies and methods should be conducted on this area in the future.

This finding of factors influencing the success of green highway projects which is useful for managers to overcome various obstacles encountered in similar projects. Moreover, considering the interaction among the influencing factors enables managers to make systematic and efficient decisions.

Developing green highways have been perceived as a major innovation to help achieve the synergy of environmental protection, economic development and social responsibility. Studying the key factors influencing the success of green highway projects and putting forward targeted suggestions are crucial for promoting the environmental protection transformation of highway construction.

Compared with most studies on the identification of key influencing factors of construction projects, this research emphasized the interaction between different factors within the system in the analysis process. The findings could provide useful references to promote the successful implementation of green highway projects.

Extensive research towards identifying the attributable cost overrun factors globally has been conducted predominantly from a survey-oriented perspective, which disregard the contextual basis on which these triggers manifest. This study aims to explore the driving factors of cost overrun in highway projects, specific to the Nigerian context.

The research used a context-based approach to seek project stakeholders’ perspectives on the key drivers of cost overrun in highway projects in Nigerian. Semi-structured interviews were conducted with client, contractor and consultant organisations involved in the provision of highway infrastructure projects in Nigeria. The collected data was analysed using a developed coding framework grounded on a case study approach, principles of inductive thematic analysis and saliency analysis to identify the key drivers.

Findings from the analysis identified triggers from macroeconomic, societal, leadership and project management perspectives with synergistic relationships with each other based on prevalence and significance. Among the key triggers is a delay in work progress, political instability, adverse weather, social issues, delay in progress payment to contractors and modification of project scope. In conclusion, the triggers of cost overrun in highway projects are contextually driven by the complex nature of the project management, societal, macroeconomic and leadership triggers specific to the Nigerian context.

The research was limited to only highway infrastructure projects in Nigeria. Furthermore, the findings are based on a small sample size, and thus, caution must be taken before applying the outcome of this study in a generalised way to other contexts.

Practically, the stakeholders i.e. client, contractors and consultants should acknowledge the contextual circumstances in which each of the triggers takes place, which will aid in developing pragmatic measures and make the right decisions towards addressing these triggers during any highway construction project in Nigeria and enhance the chances of project success.

The context-based approach applied in this study is expected to provide a new insight in understanding the triggers of cost overruns, especially in highway projects in Nigeria and indeed other developing countries with similar governance characteristics