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Open Access
Article
Publication date: 6 September 2021

Yujie Li, Tiantian Chen, Sikai Chen and Samuel Labi

The anticipated benefits of connected and autonomous vehicles (CAVs) include safety and mobility enhancement. Small headways between successive vehicles, on one hand, can cause…

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Abstract

Purpose

The anticipated benefits of connected and autonomous vehicles (CAVs) include safety and mobility enhancement. Small headways between successive vehicles, on one hand, can cause increased capacity and throughput and thereby improve overall mobility. On the other hand, small headways can cause vehicle occupant discomfort and unsafety. Therefore, in a CAV environment, it is important to determine appropriate headways that offer a good balance between mobility and user safety/comfort.

Design/methodology/approach

In addressing this research question, this study carried out a pilot experiment using a driving simulator equipped with a Level-3 automated driving system, to measure the threshold headways. The Method of Constant Stimuli (MCS) procedure was modified to enable the estimation of two comfort thresholds. The participants (drivers) were placed in three categories (“Cautious,” “Neutral” and “Confident”) and 250 driving tests were carried out for each category. Probit analysis was then used to estimate the threshold headways that differentiate drivers' discomfort and their intention to re-engage the driving tasks.

Findings

The results indicate that “Cautious” drivers tend to be more sensitive to the decrease in headways, and therefore exhibit greater propensity to deactivate the automated driving mode under a longer headway relative to other driver groups. Also, there seems to exist no driver discomfort when the CAV maintains headway up to 5%–9% shorter than the headways they typically adopt. Further reduction in headways tends to cause discomfort to drivers and trigger take over control maneuver.

Research limitations/implications

In future studies, the number of observations could be increased further.

Practical implications

The study findings can help guide specification of user-friendly headways specified in the algorithms used for CAV control, by vehicle manufacturers and technology companies. By measuring and learning from a human driver's perception, AV manufacturers can produce personalized AVs to suit the user's preferences regarding headway. Also, the identified headway thresholds could be applied by practitioners and researchers to update highway lane capacities and passenger-car-equivalents in the autonomous mobility era.

Originality/value

The study represents a pioneering effort and preliminary pilot driving simulator experiment to assess the tradeoffs between comfortable headways versus mobility-enhancing headways in an automated driving environment.

Details

Frontiers in Engineering and Built Environment, vol. 1 no. 2
Type: Research Article
ISSN: 2634-2499

Keywords

Article
Publication date: 13 June 2016

Michelle S. Dojutrek, Samuel Labi and J. Eric Dietz

Transportation project evaluation and prioritization use traditional performance measures including travel time, safety, user costs, economic efficiency and environmental quality…

Abstract

Purpose

Transportation project evaluation and prioritization use traditional performance measures including travel time, safety, user costs, economic efficiency and environmental quality. The project impacts in terms of enhancing the infrastructure resilience or mitigating the consequences of infrastructure damage in the event of disaster occurrence are rarely considered in project evaluation. This paper aims to present a methodology to address this issue so that in prioritizing investments, infrastructure with low security can receive the attention they deserve. Second, the methodology can be used for prioritizing candidate investments from a budget that is dedicated specifically to security enhancement.

Design/methodology/approach

In defining security as the absence of risk of damage from threats due to inherent structural or functional resilience, this paper uses security-related considerations in investment prioritization, thus introducing robustness in such evaluation. As this leads to an increase in the number of performance criteria in the evaluation, the paper adopts a multi-criteria analysis approach. The paper’s methodology quantifies the overall security level for an infrastructure in terms of the threats it faces, its resilience to damage and the consequences in the event of the infrastructure damage.

Findings

The paper demonstrates that it is feasible to develop a security-related measure that can be used as a performance criterion in the evaluation of general transportation projects or projects dedicated specifically toward security improvement. Through a case study, the paper applies the methodology by measuring the risk (and hence, security) of each for multiple infrastructure assets. On the basis of the multiple types of impacts including risk impacts (i.e. increase in security) because of each candidate investment, the paper shows how to prioritize security investments across the multiple infrastructure assets using multi-criteria analysis.

Originality/value

The overall framework consists of the traditional steps in risk management, and the paper’s specific contribution is in the part of the framework that measures the risk. The paper shows how infrastructure security can be quantified and incorporated in the project evaluation process.

Details

International Journal of Disaster Resilience in the Built Environment, vol. 7 no. 3
Type: Research Article
ISSN: 1759-5908

Keywords

Open Access
Article
Publication date: 13 July 2022

Jiqian Dong, Sikai Chen, Mohammad Miralinaghi, Tiantian Chen and Samuel Labi

Perception has been identified as the main cause underlying most autonomous vehicle related accidents. As the key technology in perception, deep learning (DL) based computer…

Abstract

Purpose

Perception has been identified as the main cause underlying most autonomous vehicle related accidents. As the key technology in perception, deep learning (DL) based computer vision models are generally considered to be black boxes due to poor interpretability. These have exacerbated user distrust and further forestalled their widespread deployment in practical usage. This paper aims to develop explainable DL models for autonomous driving by jointly predicting potential driving actions with corresponding explanations. The explainable DL models can not only boost user trust in autonomy but also serve as a diagnostic approach to identify any model deficiencies or limitations during the system development phase.

Design/methodology/approach

This paper proposes an explainable end-to-end autonomous driving system based on “Transformer,” a state-of-the-art self-attention (SA) based model. The model maps visual features from images collected by onboard cameras to guide potential driving actions with corresponding explanations, and aims to achieve soft attention over the image’s global features.

Findings

The results demonstrate the efficacy of the proposed model as it exhibits superior performance (in terms of correct prediction of actions and explanations) compared to the benchmark model by a significant margin with much lower computational cost on a public data set (BDD-OIA). From the ablation studies, the proposed SA module also outperforms other attention mechanisms in feature fusion and can generate meaningful representations for downstream prediction.

Originality/value

In the contexts of situational awareness and driver assistance, the proposed model can perform as a driving alarm system for both human-driven vehicles and autonomous vehicles because it is capable of quickly understanding/characterizing the environment and identifying any infeasible driving actions. In addition, the extra explanation head of the proposed model provides an extra channel for sanity checks to guarantee that the model learns the ideal causal relationships. This provision is critical in the development of autonomous systems.

Details

Journal of Intelligent and Connected Vehicles, vol. 5 no. 3
Type: Research Article
ISSN: 2399-9802

Keywords

Article
Publication date: 27 June 2019

Samuel Laryea

Construction project management outcomes in the literature typically portray significant deviations from expected outcomes. Various theories from studies that focus superficially…

1463

Abstract

Purpose

Construction project management outcomes in the literature typically portray significant deviations from expected outcomes. Various theories from studies that focus superficially on causes of project cost and time overruns rather than root causes have not addressed this problem. The need is for a better understanding of how procurement strategy provides a fundamental means to address this problem. The purpose of this paper is to examine the procurement strategy used to deliver a new universities project in South Africa within budget and to ascertain its influence on the outcomes.

Design/methodology/approach

A case study was designed to provide a comprehensive and intensive methodology to identify and examine the construction procurement strategy and its influence on the project outcomes. Document analyses and semi-structured interviews were used to collect data on the construction procurement strategy and outcomes from the client team.

Findings

The evidence brought forward demonstrates that the successful outcome was largely a consequence of the client team, procurement strategy and systems of delivery. However, the collaborative procurement strategy formed the basis of the successful project delivery and outcomes. A general observation from the data is that an appropriate construction procurement strategy developed by an experienced client team and proactively implemented by an integrated delivery team working collaboratively is likely to achieve the intended project outcomes.

Practical implications

The findings show three critical keys to achieving intended outcomes – people, procurement strategy and systems of delivery at the governance, portfolio, programme and project management levels.

Originality/value

The value of this paper lies in using a comprehensive methodology to study the relationship between procurement strategy and outcomes. The findings can be applied by client teams to achieve better outcomes and value for money in infrastructure projects.

Details

Engineering, Construction and Architectural Management, vol. 26 no. 9
Type: Research Article
ISSN: 0969-9988

Keywords

Article
Publication date: 3 October 2019

Mustafa Jahangoshai Rezaee, Samuel Yousefi and Ripon K. Chakrabortty

Analyzing factors of delays in construction projects and determining their impact on project performance is necessary to better manage and control projects. Identification of root…

Abstract

Purpose

Analyzing factors of delays in construction projects and determining their impact on project performance is necessary to better manage and control projects. Identification of root factors which may lead to project delay and increased cost is vital at the early or planning stage. Better identification of delay factors at the early stage can help the practitioners to reduce their impacts over the long run. Hence, the purpose of this paper is to propose an intelligent method to analyze causal relationships between delay factors in construction projects. The proposed approach is further validated by a real case study of the construction projects in West Azerbaijan province in Iran.

Design/methodology/approach

During the first phase, the fuzzy cognitive map (FCM) is drawn to indicate the causal relationships between the delay factors and the evaluation factors. For this purpose, the causal relationships between 20 delay factors and four evaluation factors are considered. Afterward, the effect of each factor on management goals is evaluated by using a hybrid learning algorithm. Delay factors are further prioritized by applying fuzzy data envelopment analysis (FDEA). In the second phase, an interpretive structural modeling (ISM) is employed to determine the root causes of delay factors.

Findings

Results of the first phase show that “supervision technical weaknesses for overcoming technical and executive workshop problems” and “Inaccurate estimation of workload, required equipment and project completion time” are the most significant delay factors. In contrary, “non-use of new engineering contracts” has the lowest impact on the management goals. Meanwhile, the results of the second phase conclude that factors like “Inaccurate estimation of workload, required equipment and project completion time” “weakness of laws and regulations related to job responsibilities” and “lack of foreseen of fines and encouragements in the contracts” are the most significant root factors of delay in construction projects.

Originality/value

This paper integrates three methods including FCM method, FDEA and ISM. In the first phase, FCM is drawn according to the experts’ opinions and concerning management goals and delay factors. Later, these factors are prioritized according to the results of running the algorithm and using the FDEA model. The second phase, the seven-step in the ISM methodology, is done to identify the root factors. To ensure that the root factors of the delay are at a lower level of hierarchical structure, delay factors are partitioned by drawing the ISM model.

Details

International Journal of Managing Projects in Business, vol. 14 no. 2
Type: Research Article
ISSN: 1753-8378

Keywords

Article
Publication date: 3 April 2017

Samuel Famiyeh, Charles Teye Amoatey, Ebenezer Adaku and Collins Sena Agbenohevi

In Ghana, the duration of construction projects from inception to completion is becoming a great concern, recently, especially among clients and beneficiaries, because of the…

10403

Abstract

Purpose

In Ghana, the duration of construction projects from inception to completion is becoming a great concern, recently, especially among clients and beneficiaries, because of the rising interest rates, inflation, development plan targets, among other factors. Hence the need to understand the causes of delays and cost overrun in the construction sector has become more important than ever. This study therefore aims to identify the major factors underlying time and cost overruns in projects related to the education sector in Ghana to proffer practical solutions in addressing them.

Design/methodology/approach

The study conducted a survey among clients’ consultants and representatives of the contractors working on about 60 government school projects. A relative importance index was used to determine the relative effects of the factors causing construction time and cost overruns.

Findings

The key factors causing construction time overrun were: financial problems, unrealistic contract durations imposed by clients, poorly defined project scope, client-initiated variations, under-estimation of project cost by consultants, poor inspection/supervision of projects by consultants. Other factors were underestimation of project complexity by contractors, poor site management, inappropriate construction methods used by contractors and delays in the issuance of permits by government agencies. Factors affecting cost overruns were financial difficulty by client, delays in payments of completed works, variations in designs, lack of communications plans, poor feasibility and project analysis, poor financial management on site and material price fluctuations.

Research limitations/implications

The research was limited to only the educational sector projects.

Practical implications

Practically, this study highlights for the construction sector the critical factors causing project time and cost overruns in Ghana. Identification of these factors provides the basis for pragmatic solutions to enhance the chances of project success.

Social implications

The identification and solutions to project time and cost overruns, especially for educational sector projects, contribute toward making public goods more affordable and accessible to most citizens, particularly in developing countries.

Originality/value

This study contributes to the debate on factors causing project time and cost overruns in the construction sector especially from a developing country’s perspective.

Details

Journal of Engineering, Design and Technology, vol. 15 no. 2
Type: Research Article
ISSN: 1726-0531

Keywords

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