Ali Touran

A collision model for safety evaluation of autonomous intelligent cruise control

This paper describes a general framework for safety evaluation of autonomous intelligent cruise control in rear-end collisions. Using data and specifications from prototype devices, two collision models are developed. One model considers a train of four cars, one of which is equipped with autonomous intelligent cruise control. This model considers the car in front and two cars following the equipped car. In the second model, none of the cars is equipped with the device. Each model can predict the possibility of rear-end collision between cars under various conditions by calculating the remaining distance between cars after the front car brakes. Comparing the two collision models allows one to evaluate the effectiveness of autonomous intelligent cruise control in preventing collisions. The models are then subjected to Monte Carlo simulation to calculate the probability of collision. Based on crash probabilities, an expected value is calculated for the number of cars involved in any collision. It is found that given the model assumptions, while equipping a car with autonomous intelligent cruise control can significantly reduce the probability of the collision with the car ahead, it may adversely affect the situation for the following cars.

Calculation of contingency in construction projects

This paper presents a probabilistic model that considers the random nature of change orders and their impact on the cost and schedule of a construction project. The model incorporates uncertainties in project cost and schedule and calculates the contingency based on the level of confidence specified by the owner. It assumes a Poisson arrival pattern for change orders in a construction project. The effect of schedule delays in further increasing the project cost is considered explicitly and the effect of correlation between change orders is discussed and analytically considered. The proposed model may be used for budgeting purposes at the early stages of project development. Typical applications of the proposed model in the context of construction industry are discussed. A numerical example is presented that demonstrates the use of the model in establishing a budget contingency. The results of the example are compared with actual data from previous construction projects.

Selection of Project Delivery Method in Transit: Drivers and Objectives

This paper describes the results of research on alternative project delivery methods in transit projects in the United States. The research, sponsored by the Transit Cooperative Research Program, aimed to identify those factors that drive the decision in the choice of project delivery method. A rigorous case study analysis based on on-site structured interviews with the directors of several transit projects was used to identify decision drivers and the rationale behind the delivery method selection decision in transit agencies. The nine case studies conducted in this research represent a cross section of delivery methods, including design-bid-build/multiprime, construction manager-at-risk, design/build, and design/build-operate-maintain. The interviewees agreed that the use of alternative delivery methods have resulted in savings in schedule and cost for transit agencies. The research also found that achieving aggressive schedule compression is the most influential factor when selecting alternative delive...

A Guidebook for the Evaluation of Project Delivery Methods

This guidebook describes various project delivery methods for major transit capital projects. The guidebook also includes an evaluation of the impacts, advantages, and disadvantages of including operations and maintenance as a component of a contract for a project delivery method. The project delivery methods discussed are design-bid-build (DBB), construction manager at risk (CMR), design-build (DB), and design-build-operate-maintain (DBOM). The guidebook offers a three-tiered project delivery selection framework that may be used by owners of transit projects to evaluate the pros and cons of each delivery method and select the most appropriate method for their project. Tier 1 is a qualitative approach that allows the user to document the advantages and disadvantages of each competing delivery method. The user can then review the results of this analysis and select the best delivery method. If, at the conclusion of this analysis, a clear option does not emerge, the user then moves on to Tier 2. Tier 2 is a weighted-matrix approach that allows the user to quantify the effectiveness of competing delivery methods and select the approach that receives the highest score. The third tier uses principles of risk analysis to evaluate delivery methods. The selection framework may also be useful as a means to document the decision in the form of a Project Delivery Decision Report. The guidebook will be helpful to transit general managers, policy-makers, procurement officers, planners, and consultants in evaluating and selecting the appropriate project delivery method for major transit capital projects.

Public-Private Partnership Experience in the International Arena: Case of Turkey

AbstractPublic-private partnership (PPP) models are frequently used in construction projects worldwide. The experiences of developed and developing countries vary depending on existing legal, economical, social, and political environments. Although there are some common challenges, risks, limitations, and success factors, practicing PPP framework is also dependent on country-specific factors. In this paper, first the state of the art in frequent PPP practicing regions/countries such as Europe, the U.K., and China are summarized; and a review of PPP experience in the U.S. is presented. Then, Turkey, where different PPP models have been used for nearly three decades, is analyzed in more depth as an example for developing countries. A new PPP law has been drafted to expand the legal context and types of models and overcome the existing limitations since the first introduction of PPP projects in Turkey in early 1980s. An intensive PPP literature survey has been made to present the common success factors, risk...

Probabilistic Approach for Budgeting in Portfolio of Projects

This paper presents a mathematical model for calculating the budgetary impact of increasing the required confidence level in a probabilistic risk assessment for a portfolio of projects. The model provides a rational approach for establishing a probabilistic budget for an individual project in such a way that the budget for a portfolio of projects will meet a required confidence level. The use of probabilistic risk assessment in major infrastructure projects is increasing to cope with major cost overruns and schedule delays. The outcome of the probabilistic risk assessment is often a distribution for project costs. The question is at what level of confidence (i.e., the probability that budget would be sufficient given the cost distribution) should be used for establishing the budget. The proposed method looks at a portfolio of such projects being funded by the same owner. The owner can establish a target probability with respect to its annual budget. The model can help the owner establish confidence level ...

Optimum fleet size determination by queuing and simulation

Queuing theory applications in the field of earth-moving operations are reviewed. Using queuing theory and simulation techniques, a model is developed that can predict the productivity of one pusher and a fleet of scrapers under a given set of operating conditions. A computer program is developed for this purpose that interfaces Gaarslevs Queuing Model Program and Caterpillars Vehicle Simulation Program. The new system can consider the effect of variable inter-arrival times and bunching and road and machine conditions. The developed computer system allows the user to perform a sensitivity analysis by varying the number of scrapers, thus determining the optimum fleet size based on the lowest cost per cubic yard of production.

A Guidebook for Selecting Airport Capital Project Delivery Methods

This guidebook describes various project delivery methods for major airport capital projects. The guidebook also evaluates the impacts, advantages, and disadvantages of these various project delivery methods. The project delivery methods discussed include design-bid-build (DBB), construction manager at risk (CMR), and design-build (DB). The guidebook offers a two-tiered project delivery selection framework that may be used by owners of airport projects to evaluate the pros and cons of each delivery method and select the most appropriate method for their project. Tier 1 is an analytical delivery decision approach that is designed to help the user understand the attributes of each project delivery method and whether the delivery method is appropriate for their specific circumstance. Tier 2 uses a weighted-matrix delivery decision approach that allows users to prioritize their objectives and, based on the prioritized objectives, select the delivery method that is best suited for their project. The report will be helpful to airports with determining the most appropriate project delivery methods (e.g., DBB, DB, or CMR) for various types of airport capital projects.

Schedule contingency analysis for transit projects using a simulation approach

Abstract This paper presents a probabilistic method to establish schedule contingency levels based on percent completion of the project. The objective is providing a distribution for contingency for various percent completion levels which allows the project owner/manager to choose the schedule contingency at their comfort level. The proposed method is applied on real data from a number of US transit projects and actual schedule overruns for different phases of the project development (preliminary engineering, final design and construction) are analyzed. These values are used to establish the required contingency at the conclusion of each of the mentioned project phases. Additionally, using these values, the required contingency at various points during the construction phase (such as 25% and 50% completion) is calculated and reported. This approach can be used by project owners to plan realistic schedules during various phases of the project, providing better control on duration and the opportunity for be...

Project Management Strategies for Complex Projects: Case Study Report

Successful management of complex transportation projects requires a fundamental change in how projects are planned, developed, designed, procured, and constructed. The Strategic Highway Research Program 2 (SHRP 2) Renewal Research Project R10, Project Management Strategies for Complex Projects, is investigating strategies, tools, techniques, and methods that can be effectively used for complex project management. This report for Project R10 describes the results of Task 4 (Develop Case Studies) and a portion of Task 5 (Analyze Case Studies). Fifteen projects in the United States and three international projects were investigated through in-depth case studies to identify tools that aid project managers of complex projects to successfully deliver projects. These 18 projects represent a number of different project types, locations, project sizes, and phases of project development. The tools identified from these projects fall into two areas: project development and project execution.