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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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.
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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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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.
Subway station rehabilitation / renovation projects (hereinafter referred to as subway rehabilitation projects) are among the projects with special needs [1] in which a variety of stakeholders including the Department of Transportation (DOT), Department of Environmental Protection (DEP), Department of Historic Resources (DHR), utility companies, regulatory organizations, municipalities, and community organizations are usually involved. Some rehabilitation projects interfere with daily operations at stations; therefore, specific execution strategies such as diverting trains and working in confined spaces are required for successful completion of these projects. Execution of these strategies usually requires proper management of project-specific constraints, assumptions, and objectives and being equipped with a right set of skills and knowledge.
Subway rehabilitation projects have special characteristics which differentiate them from other types of construction projects. The most important characteristics of subway rehabilitation projects from a project planning perspective are shown in the figure below.
Key Planning and Scheduling Considerations for Subway Rehabilitation Projects
Maintaining the reliability of the existing railway transit system while following safety and punctuality guidelines is an important factor that needs to be accounted for. According to the study performed by Collins and Rowe [2], some of the unique considerations of transit projects are as follows:
Acquisition of right-of-way
Acquisition of special services
Relocation of utilities
Relocation of construction infrastructure.
These requirements are all applicable to subway rehabilitation projects; hence, they should be addressed in such a way that the typically large number of private and public stakeholders remain satisfied with the project. Based on the foregoing, it is important to investigate planning and scheduling requirements of subway rehabilitation projects to ensure these projects are executed efficiently and delivered per expectation. The following section describes special characteristics of subway rehabilitation projects in more depth:
Special services are among the distinct aspects of subway rehabilitation projects. It is important to identify different types of special services that are commonly used in these projects. The following provides a brief explanation of some of the special services frequently encountered on subway rehabilitation projects:
Diversions
Subway projects often require temporary service diversions due to interference with normal train operations. A diversion occurs when a train changes its track in a station (e.g. from a local track to an express track); whereas, a by-passing occurs when a train passes a station through its normal tack of service and without any stop. Some tasks can be performed during a by-passing, however, some tasks such as working on tracks need diversion.
Public transit systems constantly try to maximize the productivity of tracks and minimize track outages and passenger inconvenience; therefore, service diversions for maintenance, emergencies, and special events are costly and not easily coordinated. Before approving any diversion requests, all impacts (i.e., definitive and potential impacts) on the affected tracks need to be closely analyzed by the planning and operations departments; therefore, detailed planning for each diversion is of great importance in advance of subway construction, rehabilitation, or renovation projects.
Depending on the project type, location of the station, and daily average subway ridership in the station, the following considerations need to be taken into account for diversion planning:
Permissible days and hours of work during each service diversion
Number of diversions provided within a month and during the construction phase
Timeframes during which no diversion is available (e.g., holiday seasons)
Work restrictions during diversions
A so-called piggy-back diversion is scheduled when a project utilizes the available diversion opportunities of another project or a maintenance task. Piggy-backing has several benefits including:
Utilization of available diversions
Maximizing track access productivity
Minimizing track access schedule conflicts
Reducing customer inconvenience
Reducing the project expenditure
For planning of subway projects with multiple diversions, the during-diversion work should be broken down into scopes of work scheduled for each diversion based on each diversion’s calendar, sequence of activities, and open (i.e., available) work-fronts. With this method of planning, contractors and owners will be able to analyze the number of diversions required to complete the project and assess the feasibility of the tasks scheduled for each diversion. This method of planning also helps contractors make timely requests for adequate work-trains and services they need.
Efficient utilization of diversions is a crucial factor to consider in time and cost management of subway rehabilitation projects. To reduce costs and inconvenience of passengers, the activities that require a diversion should be scheduled together to the extent possible [3]. That being said, safety should not be compromised by stacking several trades in limited areas. In addition, it should be noted that inefficient use of diversion opportunities usually result in deviations from plans and cause disputes and unexpected losses.
Flagging
Some tasks that are performed on or under the tracks or in close proximity with the platforms (i.e., close to train tracks, or in certain heights above the platform) may require flaggers. Construction flaggers signal approaching trains to slow down and warn project personnel of oncoming trains. Some activities such as working on elevators, mezzanine areas, or street entrances are executed without a need for diversion and flaggers; however, some activities are planned either with service diversions or under traffic with flagging protection (i.e., without suspension of train services). Examples of activities that require flagging include surveying operations, inspections, and activities that require work- or test-trains. Operations departments usually prefer activities to be executed under traffic with flagging rather than having activities performed with diversions. Nonetheless, flagging is costly and clients and contractors typically try to minimize the use of flagging. The following steps should be performed before requesting flagging:
Identify the tasks that require flagging and determine the timeframes during which flagging is required;
Calculate the numbers of required flaggers for each task.
Determine the total number of flaggers required for each event.
Specify the flaggers’ working hours.
Consider alternative methods for minimizing the number of required flaggers. Some alternative methods include but are not limited to barricades, safety railings, and barricaded scaffolds.
Analyze the sequence of the tasks that require flagging to check if they can be done sequentially – doing so may decrease the total number of flaggers required for each event.
Work-Trains
In subway rehabilitation projects, work-trains with special equipment (such as crane and scaffold) are sometimes required. Since work-trains of a company are usually enterprise-wide resources that are shared among multiple projects, issuing timely requests and accounting for a reasonable lead-time to acquire work-trains is paramount. Some companies have guidelines for requesting and proper scheduling of work-trains as part of their enterprise resource planning system. Project planners should familiarize themselves with their company’s equipment request procedures. The following considerations need to be taken into account for requesting work-trains:
The number of required work-trains during each planning timeframe
Safety considerations in scheduling activities that involve the use of work-trains
Required modifications/additions to work-trains (e.g., mounting work platforms or cable reels)
The amount of material to be transported by each work-train
The number of required round trips
The required equipment for and the party responsible for loading/unloading work-trains
The allowable hours and locations for loading/unloading operations
The possibility of using other projects’ idle work-trains.
Conclusion
Subway rehabilitation projects have unique characteristics; and various uncertainties exist in these types of projects. Some special characteristics of subway rehabilitation projects include the need for work-trains, diversions, flaggers, and utility relocations. Keeping various stakeholders (e.g., local communities, operation and maintenance departments, utility agencies, and environmental agencies) satisfied over the course of the project is also extremely important.
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