The Association for the Advancement of the Cost Engineering (AACE International) has recently released Recommended Practice 129R-23, Linear Scheduling Method (LSM). Dr. Amin Terouhid, PE, PMP and Dr. Mirhadi, PMP, Adroit’s principal consultants, are the two primary authors of this recommended practice. This recommended Practice has been peer reviewed and approved by AACE’s planning and scheduling subcommittee members and has now been released for public review.
The AACE International Recommended Practices (RPs) contain valuable reference information and serve as references for project management, cost engineering, and construction claims professionals around the globe. These documents are regularly and carefully updated, go through multiple peer reviews and revisions before publication, and are routinely reviewed by numerous relevant practitioners. The AACE International Recommended Practices (RPs) have been subject to a rigorous peer review process and are intended to be the main technical foundation of AACE’s educational, and certification products and services.
Adroit’s consultants have previously authored other recommended practices too. They received the AACE 2018 Technical Excellence Award because of their role in authoring some of the recommended practices published by AACE international (including Recommended Practice 91R-16 Schedule Development, Recommended Practice 89R-16 Management Summary Schedule, and Recommended Practice 92R-17 Analyzing Near-Critical Paths).
Project planning and scheduling professionals use a variety of project scheduling methods depending on the type, size, and nature of projects. The linear scheduling method (LSM) is typically used on projects wherein the majority of the scope is made up of highly repetitive work elements along a horizontal or vertical alignment. Examples of these projects include pipeline, tunnel, airport runway, highway, transmission line, road resurfacing, railroad, or high-rise construction projects. An LSM schedule (also known as a linear schedule or march chart) is the graphical output of the LSM. Linear schedules use velocity diagrams, which will be described below, to represent each activity and the progress rate to be achieved (or alternatively, the progress actually achieved) over time. The schedule format typically provides planned and/or actual production rates on a time-scaled, linear format.
This recommended practice (RP) is intended to serve as a guideline, not a standard. As a recommended practice of AACE International, the main objectives of this recommended practice (RP) are to increase LSM usage and enhance project management practices by:
Providing an overview of the LSM.
Defining characteristics and applications of the LSM.
Delineating the steps and main considerations in developing, updating, and managing linear schedules.
Highlighting main considerations in interpreting linear schedules
For more information about this recommended practice see:
To find out about the strategies for the effective use of project schedules, including the use of Linear Scheduling Method (LSM), please feel free to contact us.
Project schedules are among the key project artifacts that are used as a basis for project control. They are one of the most effective ways that a project team can use to coordinate their activities. Project schedules play a key role in making such coordination and to facilitate achieving a project’s time objectives. However, project schedules can play this role only if they are prepared in a reasonable manner. The reasonableness of project schedules can be evaluated from various perspectives including consistency, clarity, completeness, and feasibility of construction plans.
The
following are some of the main considerations that need to be given to
developing project schedules to ensure they are reasonable:
The schedule is complete and entails all the activities that are needed to successfully implement the scope of work
Proper logical relationships (including finish-to-start, start-to-start-, start-to-finish, or finish-to-finish relationships along with proper lag and lead values) are used in creating the project network
An appropriate combination and choosing of activity relationships (including mandatory, preferential, and scenario-based relationships) are created to define activity dependencies
The schedule accounts for the technical, physical, and technological constraints of performing the work
The schedule meets proper contractual milestones, identifies all interim and ultimate contractual deliverables, and satisfies time and resource constraints outlined in the contract
The schedule is clear, reasonable, and complete
Different sections of the schedule are consistent in terms of the timeline, work priorities, and work sequence
As
noted above, activity dependencies are among the key main considerations in
developing well-prepared schedules. A project network not only contains project
activities but also defines activity dependencies (also known as activity ties
or activity relationships). A variety of activity dependencies exists, and activity
relationships are categorized in different ways.
Activity
dependencies can be categorized based on the nature of dependencies that exist
between project activities. From this perspective, activity dependencies are
often categorized into the following two types of dependencies:
Mandatory dependency (also known as hard logic): This relationship represents a dependency that is necessary or inherent in the nature of the work.
Discretionary dependency (also known as soft, preferred, or preferential logic): This type of dependency represents preferential logic that is used to establish a desired sequence of work despite alternative sequences that are acceptable.
It is important to note, however,
that mandatory and discretionary relationships are not the only activity relationships
that are used in project schedules. To better identify activity dependencies,
it is suggested that activity dependencies are further categorized as shown in
Figure 1.
Figure 1. Activity relationship
types
As this figure shows, mandatary
relationships can further be broken down into the following three types:
Imposed relationships: Imposed relationships are those relationships that need to be built into a project schedule to satisfy legal, regulatory or contractual requirements. An example includes a contractually-imposed requirement that mandates using a phased approach (where a portion of work has to be implemented after another portion) in completing certain elements of work.
Physical relationships: This relationship represents a dependency that has to be established between two or more activities due to the nature of the work. An example of dependencies that are inherent in the nature of the work is the need to place a foundation first before erecting a column atop the foundation.
Safety relationships: This relationship represents a dependency that has to be established between two or more activities to ensure safety considerations are accounted for in sequencing project activities. An example of a safety relationship is the need to avoid concurrent logic in scheduling two activities that cannot be undertaken simultaneously because of safety concerns (e.g., a crew that cannot work on the second floor of a building because of the ongoing work on the first floor).
Sometimes, project scheduling
professionals use scenario-based relationships to define dependencies between
project activities. The current article uses the term scenario-based to
characterize these relationships because depending on the implementation
strategy chosen to execute a project, scenario-based relationships may or may not
be used in defining work sequences. Resource relationships are examples of
scenario-based relationships. Resource relationships are often added to the
project schedule due to resource management concerns (e.g., resource
constraints).
For example, if a contractor needs
to implement two non-causally-related activities, each of which requiring a
crane, the contractor may decide to add a finish-to-start relationship between
the two activities if the contractor has only one crane in its possession. In
this example, the two activities are not causally related; however, based on
the scenario described, the contractor has established a relationship between
these two activities to satisfy its resource constraint. If the contractor had
two cranes in its possession, defining a dependency between the two activities
was unnecessary because as noted above, the activities are presumably not
causally linked. Therefore, it is reasonable to recognize the above-referenced
activity relationship as a scenario-based relationship because these
relationships may or may not be used depending on the implementation scenario
or strategy used.
Not all scenario-based relationships
are resource relationships; therefore, in Figure 1, scenario-based
relationships are broken down into the two main types of resource relationships
and others. An example of other scenario based dependencies includes a
dependency that is established between two activities based on an assumed
what-if scenario to manage a likely change in the project scope of work. This
relationship may or may not be required to be established depending on whether
the change occurs or not.
The last category of activity
relationships is improper relationships that consist of redundant, incorrect
logic, and logic loops. Incorrect logic relationships can further be
categorized into errors, missing logic, out-of-sequence, and improper use of
lags and leads. These relationships will be described in greater depth in a
future article.
Planning and scheduling
professionals need to make informed decisions in selecting and using the right
relationship type. In general, it is suggested that only mandatory
relationships are used in developing project schedules unless the use of
discretionary or scenario-based relationships is justified. Similarly, the use
of preferential relationships may not be appropriate in demonstrating that a
schedule follows a reasonable logic. It is recommended that, instead of
resource constraints, planning and scheduling professionals use resource
leveling techniques to ensure the schedule is not bounded by too many
dependencies that could have otherwise been accounted for.
Assessing activity relationships is
critical in preparing or investigating time extension requests or delay
assessments because a proper delay analysis has to be based on a reasonable
schedule. A delay analysis based on a project schedule that contains
questionable activity relationships is defective. Project planning and
scheduling, forensic scheduling experts, and claim management professionals
need to ensure project schedules are free of improper relationships. Otherwise,
the schedule will not be reliable or reasonable and it may not serve its
purpose.
Author: Dr. Amin Terouhid, PE, PMP, PSP | Principal
Consultant
If you are interested to find out more about the main
considerations in developing or evaluating project schedules, please contact us.
Adroit’s consultants have demonstrated their expertise in developing, updating,
constructability review, and forensic evaluation of project schedules and will
be able to assist. You may also be interested to read the following articles:
Schedule constructability review, what does it entail?
Project planning and scheduling professional may use different project scheduling methods and techniques for different projects depending on the type, size, and nature of projects. Repetitive scheduling techniques are used is in linear construction projects. In linear construction projects, the majority of the work is made up of highly repetitive activities. In these projects, a set of project activities are repeated in each location for the entire length of the work. Once a project activity is started and/or ended in one location, it is repeated in another location. Examples of linear construction projects include pipeline projects, highway construction, highway resurfacing and maintenance, airport runway construction and resurfacing tunnels, mass transit systems, and railroads. Because of the highly repetitive nature of the work, high-rise building projects are also often identified as linear in nature.
One of the important considerations in the planning of linear construction projects is to identify a location for the working crew to move to in a manner that its work does not interfere with the work of any other construction crew. Therefore, production rates have to be coordinated to prevent a preceding process from overtaking its succeeding process(s).
Traditional project planning and scheduling methods such as the critical path methods are typically inadequate for effective planning and scheduling of linear construction projects because these planning and scheduling methods do not account for work locations or spatial aspects and do not effectively model project activities that are repetitively performed. Due to such shortcomings, other methods such as line of balance (LOB), vertical production method (VPM), time couplings method (TCM), the repetitive project modelling (RPM), repetitive construction (REPCON), and the repetitive scheduling method (RSM) have been proposed in the literature to better satisfy the planning and scheduling needs of linear construction projects. The various repetitive scheduling techniques can be categorized into the two main classes of linear scheduling methods (LSM) and line of balance (LOB) techniques.
Line of balance techniques use three key types of charts to illustrate repetitive construction activities. These charts are objective chart, production plan, and progress chart. LOB was first used in the manufacturing industry. It starts with the end product and the ultimate output quantity and schedule in mind. This information is documented in the production plan and it is then used to establish a cumulative plan that delineates how much work ought to be delivered over time. This cumulative plan then becomes the objective chart against which the actual progress is measured using the progress chart. An example objective chart that is used in the line of balance method is shown in the figure below.
LSM schedules, however, use velocity diagrams representing each activity. The schedule format may provide the planned and actual production rates on a time-scaled format. A typical LSM diagram represents time along the X-axis (i.e., horizontal axis) and some measure of repetitive units along the Y-axis (i.e., vertical axis). This diagram also includes lines that represent all the linear activities that are involved in the completion of the repetitive units. A linear activity is a project activity that progresses along a physical path. This path is represented by the location axis in the LSM. Over the course of the project and at any point of progress along this path, the activity is completed up to that point. For instance, consider an activity that involves rough grading before finish grading in a road construction project. In this example, as the path is rough-graded, the rough-grading activity is complete up to that point of progress along the path. Once the path is rough-graded at any location, no need exists anymore to go back and rough-grade the location. Therefore, any location along the path that is behind the current work location is a work-front for succeeding activities (e.g., finish grading) to be performed. An example LSM diagram is shown in the figure below.
In a future article, further considerations in developing the linear scheduling and line of balance techniques will further be described.
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Subway station rehabilitation/renovation projects, also known as subway rehabilitation projects, are among the projects with special needs. These projects have special characteristics that differentiate them from other types of construction projects. The most important characteristics of subway rehabilitation projects from a project planning perspective are the need to account for the schedule of diversions, utility/infrastructure relocations, piggybacking opportunities, special permits, flagger availability, and work train availability.
Because of the special characteristics of subway rehabilitation projects, some considerations for scheduling these projects shall be applied with special attention and emphasis. The following provides key considerations for planning and scheduling of these projects. This list is not meant to be comprehensive. Instead, it identifies some of the key considerations that need to be given to the planning and scheduling of subway rehabilitation projects.
Identify the activities that cannot be implemented during normal service hours (e.g., the activities that need diversion of train services). Examples include activities on the platform edge and activities on, under, or near tracks. If a project involves working on several stations on the same line, the stations that are between two immediate switches can utilize the same diversion (by piggy-backing on each other). Under these circumstances, diversion-related tasks should be scheduled properly to maximize efficiency. Having multiple diversions on one line and between different switches is called double-heating. If the stations are not between two immediate switches, diversions are not usually scheduled at the same time to avoid double-heating and ensure train service interruptions are minimized.
Determine the preliminary number and type of the required diversions, work-trains, and other special services for the project. This determination will help the construction team consider diversions, work-trains, and other special services as project resources. This approach helps the construction team to identify the resources that are constrained. By using proper resource management strategies such as resource planning and optimization, the construction team can ensure it obtains access to these special services when the project needs these services.
Review the special services identified with operations departments to ensure availability. If the requested diversions cannot be accommodated during required timeframes, the scope of work, design requirements, alternative construction methods, job phasing, or the project timeline should be reviewed and revised based on the available diversion plans. In addition to time, budget, and resource constraints, the availability of diversions is one of the major constraints that impact subway rehabilitation projects.
Identify the areas and equipment that cannot concurrently be closed or taken out-of-service in each subway station to ensure of continuous and safe operation of the station. Examples include entrance stairs, platform stairs, mezzanine areas, elevators, and tracks. For instance, if two elevators in one station exist and upgrading both elevators are in the project scope of work, working on the two elevators at the same time may not be permitted.
Identify hazardous materials such as lead, asbestos, and mercury. Performing abatement operations might be necessary before the commencement of work in areas in which hazard may be present. In these cases, direct communication and coordination between the client, contractor, and environmental agencies is crucial to identify the proper course of actions. In addition, removal of these materials during the construction phase may require special permits and equipment for which contractors should plan in advance.
Identify the long-lead and client-furnished items. With respect to long-lead items, an opportunity may exist to fast-track some activities by creating an overlap between the design and procurement activities for the long-lead items. Moreover, early order placement for long-lead items plays an important role in making sure that long-lead items will be delivered to the project in a timely manner. In addition, the construction management needs to properly identify the client-furnished items and account for the possibility of receiving these items later than expected.
Identify the activities that are supposed to be executed in areas that are not under the authority of the construction team. Examples include utility relocations or working in a public street. In addition, it should be determined if these activities require additional permits (e.g., DOT permits). The project team should be aware that these tasks have the potential to delay the project to a great extent because the project team usually has little control on expediting the permit application, inspection, or review processes.
In sum, from a project planning perspective, some of the key characteristics of subway rehabilitation projects that differentiate these projects from many other construction projects include the need to account for the schedule of diversions, utility/infrastructure relocations, piggybacking opportunities, special permits, flagger availability, and work-train availability. As such, some considerations for planning and scheduling of these projects shall be applied with special attention and emphasis. This article briefly discussed some of these requirements.
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The Association for the Advancement of the Cost Engineering (AACE International) has recently released Recommended Practice 89R-16 Management Summary Schedule. Dr. Mirhadi, Adroit’s CEO and one of Adroit’s principal consultants is one of the two primary authors of this recommended practice. The AACE International Recommended Practices (RPs) are intended to be the main technical foundation of AACE’s educational, and certification products and services. The RPs are a series of documents that contain valuable reference information that has been subject to a rigorous review process and recommended for use by AACE’s Technical Board and they become references for project management practitioner throughout the world.
This recommended practice (RP) characterizes management summary schedules, describing their intended use, and identifies considerations for developing and updating these summary schedules. It also addresses roles and responsibilities relating to, and considerations in, communicating management summary schedules to ensure these schedules are used as effective planning, scheduling, and control tools in projects. This RP for management summary schedules is intended to be a guideline, not a standard. Here is the link to an excerpt from this recommended practice. For more information about the strategies for the effective use of project schedules, please feel free to contact us.
This article is part of a technical article, entitled Planning and scheduling requirements of subway station rehabilitation/renovation projects, that Adroit’s competent professionals have authored and presented in AACE International’s 2016 Annual Meeting in Toronto.
To identify the major challenges in time management of subway rehabilitation projects, the authors of this technical article conducted a series of semi-structured interviews with senior managers and professionals with extensive experience in subway rehabilitation projects [1]. The following provides a summary of findings from these interviews:
Special Services
The availability and proper management of special services and resources, such as diversions, flaggers, work-trains, and inspectors are considered among the key challenges of subway rehabilitation projects. These resources and services are usually enterprise-wide shared resources in transit companies. Since different departments within transit companies (e.g., operation, maintenance, and capital improvement departments) have their own prioritized projects, these services are not necessarily assigned with respect to the prioritization specified by other agencies.
Establishing shared goals as well as prioritizing and scheduling subway rehabilitation projects in agreement with or with consideration of the priorities announced by other departments can mitigate risks that are likely to be faced due to shared nature of these resources. For instance, awarding too many contracts during a relatively short timeframe may lead to an over-allocation of enterprise resources which may jeopardize successful completion of these projects. Therefore, it is important for the enterprise to efficiently utilize shared resources by implementing effective program and enterprise resource management practices.
In developing time schedules for subway rehabilitation projects, planning for acquisition of special services plays an important role. Backup and risk response plans should always be in place in the event these services do not become available as planned.
Design Management
Among many practices used for effective design management, integrated design management, proper use of building information modeling (BIM), and efficient coordination among different trades are among the most important factors that play important roles in preventing construction delays. The following provides a summary of the most common design-related causes of delays in subway rehabilitation projects:
Long or more than expected time to review and approve drawings and making ambiguous or unclear comments on shop drawings prepared by contractors are common causes of delay that can be prevented by providing effective design management support. These issues are seen more frequently in areas that are complex in nature or require special engineering expertise (e.g., communication and electrical drawings).
For station equipment and material selection during basic or detailed engineering, close attention should be given to the availability of the chosen items to ensure they are easily-purchasable from local markets. Subway rehabilitation projects are sometimes delayed as a result of either the contractor’s inability to find requested or specified material or due to the long lead time necessary to procure certain items. An example for this condition is special architectural materials that are chosen to match the material used in existing or adjacent areas.
Since subway rehabilitation projects are mostly small to medium size projects, they are typically executed using a design-bid-build delivery system [2]. Nonetheless, the quality of design plays an important role in successful implementation of subway rehabilitation projects and ensuring they are completed on-time and on-budget.
Design changes usually occur due to technical or technological requirements, special needs of operations and maintenance departments, emergency, and change in project prioritization. During early phases of subway projects, design changes are significantly less costly, especially if the changes are initiated prior to contract award. As soon as construction contracts are awarded, design changes become significantly more difficult to manage and they typically result in substantial cost and time impacts.
Utility Relocations
Some subway rehabilitation projects require construction teams to work in or under public streets with complex utility systems such as sewer lines, gas, water, electrical, phone, fiber optic, and storm drains. These utilities are under the authority of different agencies. For relocations of these lines, the project team needs to fully involve proper agencies, and execute relocation activities with close coordination with all affected parties. However, the relocation work is sometimes executed by utility agencies. In these cases, construction contractor can only oversee the on-site operations and cannot interfere or be actively involved with relocation operations. Since utility relocations and maintenance work are executed throughout a year, various changes may occur to a utility line in a short period of time. Therefore, it is important to note that the existing as-built drawings are not always up-to-date and accurate.
Even if the design team considered the latest as-built drawings of utility lines for a design subject, it is good practice to verify the accuracy of as-built drawings to ensure construction work will not encounter any differing site conditions. A close coordination with utility agencies, achieved through either direct contact or liaisons, is required to ensure the accuracy of as-built utility drawings.
Due to many uncertainties involved in in utility relocation work, relocation operations have the potential to significantly delay subway projects. Establishing proper channels of communication and coordination between transit companies, contractual parties, and local utility agencies is essential to mitigate risks.
Performance of Contractors
Despite their complexity, station rehabilitation projects are not usually considered among large or mega projects from the budget perspective. As a result, large construction contractors are not usually interested in attending bid processes for these projects. The high profit margin of large construction contractors and low chance of winning the bid are other reasons that large construction contractors are not usually involved in public projects for rehabilitation of subway stations. Subway rehabilitation projects are typically complex and have special needs. Limited technical and managerial capacities of small construction contractors (e.g., limited capabilities in project management in general and in execution planning, resource planning, and scheduling in particular) may adversely impact the successful implementation of subway rehabilitation projects. The risks become greater if a contractor / subcontractor overly commits to too many projects at the same time because under these conditions, resource management becomes more challenging.
Project team
In addition to the performance of contractors, the availability and quality of clients’ project teams play an important role in effective time management of subway rehabilitation projects. Key examples of the required capabilities and personal skills include having the required knowledge and experience, having effective communication skills, dedication, making on-time and decisive decisions, and adherence to decisions made.
Organizational processes
Late approval of additional work orders (AWO), late issuance of notices to proceed (NTP), and untimely approval of change orders frequently cause delays in subway rehabilitation projects. Improving organizational procedures and effective use of operational management practices can significantly increase the productivity of public transit companies and improve organizational capabilities of these agencies in effective project management. Examples of processes to improve organizational performance in project management include coordination processes, procedures for issuing task orders, review and approval processes, and contract management.
Our posts to the Insights page share fresh insights and seasoned advice about many project and construction management topics. To have the Insights monthly newsletter delivered automatically to your email inbox, please subscribe here.
This article is part of a technical article, entitled Planning and scheduling requirements of subway station rehabilitation/renovation projects, that Adroit’s competent professionals have authored and presented in AACE International’s 2016 Annual Meeting in Toronto.
As discussed in previous articles, subway rehabilitation projects have special characteristics; therefore, some considerations for scheduling these projects shall be applied with special attention and emphasis [1]. The following provides key considerations for planning and scheduling of these projects:
Constructability and phasing Review
Constructability and phasing review in early stages of work (i.e., design phase) is an important aspect of time management for subway construction projects. The constructability and phasing review should cover the entire project scope and be done in such a way that the number of required diversions (occasions for service interruption), work-trains, and flaggers be minimized. The following figure provides an example work breakdown structure for s subway rehabilitation project.
An Example Work Breakdown Structure of a Subway Rehabilitation Project
Constructability review is a construction management technique that reviews construction processes to minimize design errors, ambiguous specifications, costly, difficult-to-bid or difficult-to-implement features [2,3,4]. Constructability and phasing review helps the stakeholders to study the feasibility of the execution plan and to ensure that the project can be completed either with safe and continuous operation of trains or during planned diversions. In some cases, the constructability study may result in design changes to make the construction phases feasible. One of the key outputs of the constructability and phasing review process is the list of constraints that should be taken into account during construction.
To efficiently develop the phasing plan, the project team should consider various factors including, but not limited to:
The activities that cannot be executed during normal service hours (i.e., the activities that need diversion of train services) should be identified. Examples include activities on the platform edge and activities on, under, or near tracks. If a project involves working on several stations on the same line, the stations that are between two immediate switches can utilize the same diversion (by piggy-backing on each other). Under these circumstances, diversion-related tasks should be scheduled properly to maximize efficiency.
Having multiple diversions on one line and between different switches is called double-heating. If the stations are not between two immediate switches, diversions are not usually scheduled at the same time to avoid double-heating and ensure train service interruptions are minimized.
The preliminary number and type of the required diversions, work-trains, and other special services for the project should be determined.
The special services identified should be reviewed with operations departments to ensure availability. If the requested diversions cannot be accommodated during required timeframes, the scope of work, design requirements, alternative construction methods, job phasing, or the project timeline should be reviewed and revised based on the available diversion plans. In addition to time, budget, and resource constraints, the availability of diversions is one of the major constraints that impact subway rehabilitation projects.
In each subway station, the project team needs to identify the areas and equipment that cannot concurrently be closed or taken out-of-service to ensure of continuous and safe operation of the station. Examples include entrance stairs, platform stairs, mezzanine areas, elevators, and tracks. For instance, if there are two elevators in a station and upgrading both elevators are in the project scope of work, working on the two elevators at the same time may not be permitted.
Some old subway stations may contain hazardous materials such as lead, asbestos, and mercury. As such, performing abatement operations might be necessary before the commencement of work in certain areas. In these cases, direct communication and coordination between the client, contractor, and environmental agencies is crucial to identify proper course of actions. In addition, removal of these material during the construction phase may require special permits and equipment for which contractors should plan in advance.
The long-lead and client-furnished items should be identified.
The activities that are supposed to be executed in areas that are under the authority of other agencies need to be identified. Examples include utility relocations or working in a public street. In addition, it should be determined if these activities require additional permits (e.g., DOT permits). The project team should be aware that these tasks have the potential to delay the project to a great extent because the project team usually has little control on expediting the permit application, inspection, or review processes.
Program management
One of the key inputs required to review/revise project prioritizations, manage workloads, and allocate shared resources (e.g., special services) is an integrated and enterprise-wide program control system. Having a centralized database to store project records not only facilitates decision making, but also increases the reliability of the decisions made. For this purpose, tools such as the enterprise-based Oracle® Primavera P6™ Professional Project Portfolio Management can be used [5]. Appropriate procedures should be in place to standardize input data from different departments and to ensure that project records are updated on a regular basis.
Considerations for special activities
The tasks that have special prerequisites or require special considerations should be identified in early stages of project planning. Examples include:
Removing, repackaging, transportation, and disposal of mercury, lead, or asbestos. Containing materials may require acquisition of special licenses and permits. These permits should be considered as predecessors for related activities.
Working in or impacting areas under the authority of other agencies may require permit acquisition. For instance, working in public streets or bringing heavy equipment to certain areas may need permission form the DOT; and obtaining these permits should be defined as a predecessor for related activities. The activities that impact or interrupt the operation services of equipment, systems, or utilities under the authority of other agencies, such as removing or placing a communication system need to go through a bulletin approval process. The purpose of bulletin is to support continued operations of the systems and equipment by having backup plans in place. The bulletin should be reviewed and approved by different client’s departments such as operations and planning, maintenance of way, and system safety groups. As such, the bulletin initiation and approval are prerequisites for the related construction tasks. The review and approval process should be initiated in a timely manner to ensure no delays occur.
Working in historic areas: If the project scope involves working in historic areas of a station, special permits such as permits from the local historic preservation office may be required.
Some activities such as utility relocation work may need to be performed by other agencies; therefore, it is important that the project team obtains sufficient information (e.g., forecasted start and finish dates or forecasted durations, calendars, constraints, execution plans, and intended activity sequences) about these activities to ensure possible conflicts can be resolved in a timely manner.
Sometimes, subway rehabilitation projects require the acquisition or procurement of long-lead items (e.g., special signal equipment); therefore, it is important that planning and scheduling professionals timely start the process of obtaining long-lead items. They also need to perform periodic reviews to ensure that the delivery of the long-lead items are on schedule.
Calendar
Working days and shifts that are available for the scheduled activities and resource availability dates denoting when a resource is available for work on the project are to be revisited depending on the types of activities, timeline of receiving proper permits, timeline of diversions, interfaces with other agencies, locations where those activities are executed, and whether activities are performed in or impact other agencies’ areas of work.
For instance, the project team may need to modify the project working days and/or shifts based on the moratorium period and subway station service hours. Some diversions may be scheduled only for few hours, during night, or during weekends; therefore, the calendars assigned to related tasks should be set to hourly, nightly, or other calendar types as needed. Incorporating multiple calendars in project schedules is recommended to account for availability times for scheduled activities, project resources, agencies resources, special services (i.e., diversions in particular).
It is important to note that due to the nature of some subway rehabilitation projects, special services such as diversions, may become one of the key drivers of the project completion date. Special schedules such as look-ahead schedules with short time periods should be used in these cases to plan and monitor the project work at a detail level. Otherwise, unavailability of resources or special services may adversely affect service utilizations and result in significant delays and damages.
Considerations for updating schedules
Planning and scheduling professionals need to pay special attention to updating project schedules in subway rehabilitation projects (see AACE® International recommended practice 53R-06 [6] for minimum considerations for schedule update reviews). Updating schedules helps to determine remaining tasks or portions of tasks, identify the number and types of special services required to complete the projects, and update enterprise resource plans. It also helps clients minimize service diversions and maximize efficiency of planned services by what-if analyses, piggybacking, distributing resources, and re-phasing of projects. It is important to ensure that project schedules are developed and updated in such a way that no conflicts exist with pre-determined phasing restrictions and the schedule does not use more than the contractually agreed number of services.
Another important consideration for effective scheduling of subway rehabilitation projects is compatibility of look-ahead schedules with updated project control schedules (i.e., detailed schedules). Since look-ahead schedules highlight the near-term priorities and identify work-fronts, it is important that look-ahead schedules do not contradict updated project control schedules. Look-ahead schedules should be prepared based on and after adding more detailed scheduling information to project control schedules. On the other hand, if the contractor updates the look-ahead schedule based on the latest and up to date project information, the contractor should ensure that project control schedules are updated accordingly.
Determining activity durations
For estimating durations required for review/approval of contractor submittals by public transit companies, contractors need to consider sufficient time for all steps of the process including submission, review, resubmission, and approval steps. Following the guidelines provided in recommended practice 32R-04 [7] for determining activity durations is recommended to ensure all important considerations are taken into account. Sometimes, construction contracts define key expected durations such as maximum allowable duration for submission, review, and approval; therefore, it is important to review the contracts prior to developing project schedules.
Another important consideration for scheduling subway rehabilitation projects is inspection times. Inspections are among the special considerations for these types of projects and adequate durations need to be accounted for to ensure inspection times are not under-estimated during schedule development or updating processes.
Impact/delay analysis
Proper record keeping is important in contemporaneous cause-and-effect analysis of project changes and delays. Establishing an effective change management system will help to avoid unnecessary and costly investigations in case of any disputes. As soon as a change is introduced or an AWO is discussed, its impact on the project schedule should be investigated and outcomes need to properly be communicated with relevant parties in a timely manner. All assumptions and basis documents for impact analyses should also be properly recorded.
Conclusion
Subway rehabilitation projects have unique characteristics; and various uncertainties exist in these types of projects. Too many variables and uncertainties make time management of these projects challenging. Addressing the challenges in advance and effective risk response planning play important roles in successful execution of these projects. This article highlighted some the most important considerations for successful time management of these projects. Some of these considerations include constructability and phasing review, effective program management, considerations for special activities, considerations in the use of calendars, considerations for updating schedules, considerations in determining activity durations and in performing schedule analysis.
References:
[1]. M Mirhadi Fard, Planning and scheduling requirements of subway station rehabilitation/renovation projects, AACE International’s 2016 Annual Meeting, Toronto
[2]. AACE® International, RP 30R-03 Implementing Project Constructability, AACE® International, Morgantown, WV, USA.
[3]. AACE® International, RP 48R-06 Schedule Constructability review, AACE® International, Morgantown, WV, USA.
[4]. Construction Industry Institute (CII), Constructability: A Primer, Publication RS3-1 (July), CII, Austin, Texas, 1986.
[5]. Owen, JK, Criss, B., Managing Los Angeles $40 Billion Transportation Program with P6. AACE® International Transactions, PM.05, 2010.
[6]. AACE® International, RP 53R-06 Schedule Update Review— As Applied in Engineering, Procurement, and Construction, AACE® International, Morgantown, WV, USA.
[7]. AACE® International, RP 32R-04 Determining Activity Durations, AACE® International, Morgantown, WV, USA.
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