Title: Modular Station Design
Phase(s): Pre-Preliminary Engineering, Preliminary Engineering and Final Design
The Los Angeles Metro Rail Red Line is an 18.0 mile underground heavy rail program which began in 1986 with the start of construction on its initial segment. In June 1992, the agency's engineering and construction entity presented an initiative to develop a Modular Station Design concept for application in the design of underground stations for future Red Line segments. Since 1992, the Los Angeles County Metropolitan Transit Authority (LACMTA) has been pursuing refinement of the modular station design concept and increased development and use of Computer Assisted Design and Drafting (CADD). The initiative coincided with a conversion of design methodology from manual design and drafting practices to Computer Assisted Design and Drafting (CADD). Prior to these activities, each station had been designed relatively independently. RCC believed that the modular approach to station design would significantly reduce the number of field changes, minimize construction cost growth and improve the accuracy of cost estimates.
The Engineering Management Consultant (EMC) implemented the development of a standardized form of room layouts and modules for what was defined as standardized and interchangeable components. The role of the sub-consultant section designers was to define station finishes and the site specific features of the stations. The EMC estimated that the time taken to perform preliminary design started at 45,000 hours for the first station and declined to 14,000 hours for the fifth station in the design schedule.
2. The Lessons
During the past two years, there has been an ongoing refinement of the modular design concept, including Value Engineering of the emergency ventilation system. As a result of the refinements and the evolution and growth of the use of CADD, Preliminary Engineering can now be performed much more efficiently.
Standardized elements of the design process are defined as:
- Main Station Box
- Ancillary spaces
- Mechanical and electrical equipment
- Certain structural elements including crossover structures
- Circulation elements including loading platforms, public access and emergency egress
Site specific elements are defined as:
- Entrances, plazas and surface structures responsive to local environmental concerns
- Architecture and artwork sensitive to local influences
- Station planning responsive to future joint development or intermodal transit opportunities
In order to accomplish the overall design goals and objectives in a timely and cost effective manner, and in concert with the subdivision of work between the standardized and site specific elements, design responsibilities have been profiled, with the EMC responsible for:
- Project Management and Quality Assurance
- Main Station Structural Box including ancillary spaces, mechanical and electrical equipment, air shafts and exit corridors
- Interior finishes in non-public areas
The section designers and artists are responsible for:
- Entrance structure(s)
- Interior finishes in public areas
- Air shafts and exit corridors outside of the Main Station Structural Box
- Site work, civil and utility work
The proof of the value of any Lessons Learned program lies in the advantages that any particular lesson brings to the project as a whole. While not yet fully defined due to ongoing improvements to the program and future measurements of success, the current actual or envisioned advantages include:
- Reduced design costs due to diminished engineering and drafting
- Reduced construction costs through continuous improvements in design documents, thus minimizing changes, with the understanding that this advantage is most probable only if more than one station is included in a contract
- Improvement in the quality of design and construction, since standardization traditionally accelerates learning curves, reduces errors and, in some cases, allows more time for checking
- Reduction of maintenance costs, since standard room and equipment layouts simplify maintenance operations
- Ability to provide prototypes for early planning, with station footprint requirements being used to identify transit access and joint development potential
The concept of modular design can succeed on a project whenever the use of CADD is maximized and where the repeating physical elements, essential by definition, are in place.
Modular station design affords this and similar projects the opportunity to experience significant costs savings, greater control over schedules and improved quality in both the design and construction processes.