2.2 Practical Design Process

2.2.1 What is Practical Design?

Practical Design (PD) is a flexible approach to engineering where projects are evaluated throughout the development lifecycle to look for opportunities to lower project costs. PD looks to address the problem of “how do we do more with less” to maximize system-wide improvements. The approach focuses on maximizing improvements to the roadway system as a whole rather than maximizing improvements to a few locations. PD solutions aren’t just limited to reducing construction costs, they also can reduce operating and maintenance costs that are sometimes significantly higher than the original construction cost. PD encourages innovation and flexibility and requires more information and a higher level of analysis when defining and deciding on the most appropriate solution to a particular problem.

Practical Design is not a new or unique concept. Development of 3R design standards was one of the first examples of PD.

PD places emphasis upon solutions that contribute to the overall condition and function of the entire corridor instead of attempting to achieve the most desirable condition for a single project. PD has increased the ability of many states to deliver more cost-effective design solutions, without compromising safety or quality while enhancing the overall transportation system.

2.2.2 Practical Design Principles

The foundation of PD encompasses four principles that should be applied during the planning of all projects. Designers should define and document the project purpose and need
by specifying the problem to be solved and the future goals of the corridor/system to be achieved by the proposed project. Instead of “designing to the manual”, a “designing to the purpose and need” philosophy should be implemented. As a result, Design Exceptions and Design Waivers are strategically used, but must be adequately supported.

The typical approach of each project’s design has been to improve the specific project as much as possible with the budgeted resources (i.e., using desirable design criteria values). Maximizing improvements in one location may not be the best allocation of resources. PD is an alternative approach to generate the best return of investment. The general principles that guide PD are outlined in the following subsections.

2.2.2.1 Sound Engineering Judgment

Designers should rely upon the application of sound engineering judgment when considering design alternatives and solutions. Design decisions should be driven by common sense, context awareness and sensitivity, and innovation. Over-reliance upon traditional design standards and approaches tends to predetermine the outcome without adequate consideration for alternative, more practical solutions.

2.2.2.2 “Design Up” Philosophy

Designers should employ a “design up” philosophy to project design. Rather than starting with the “desirable” condition and often being forced to remove items to meet project scope and budget, the designer should consider the existing condition of the facility as the baseline condition, and “design up” from that point to meet the project’s purpose and need. Often, the result is a facility that is safe, practical, and less costly than anticipated. Any work beyond the purpose and need of the project is an inefficient use of resources that would likely yield a higher return if invested elsewhere. The designer should perform a cost-benefit analysis of proposed work and its effectiveness to meet the project’s purpose and need.

2.2.2.3 Get the Project Scope Right

The purpose and need statement, documented in the DSR serves as the basis for system-wide improvements and individual project development. Any features that do not directly support the purpose and need should be reevaluated, redesigned, or eliminated. PD reduces the tendency for “scope creep” by designing to, without exceeding, the purpose and need for the project.

2.2.2.4 Safer System Focus

All projects must be as safe, or safer, than the existing condition.
Careful consideration should be given to alternative strategies and creative approaches to mitigate safety concerns.

Designers are encouraged to design toward solutions that optimize the condition and performance of the corridor, rather than attempting to achieve perceived individual project perfection.

Targeted investments in specific locations throughout a corridor can have a compounding positive impact upon the overall corridor, more so than a large investment in a single location within the corridor. For example, adding a series of right turn lanes along a corridor versus a full rehabilitation to reduce operational challenges.

Practical Design’s purpose is to “build good projects everywhere – rather than perfect projects somewhere.”

- Missouri DOT 2005 Strategic Objective to Implement PD

There is not a methodology or flowcharted process for the application of PD to determine what scope and cost of a project will yield an optimized system. However, when combined with the Performance Based Design process explained in the following section, designers will, over time and with experience, develop a feel for the proper application of PD for various project situations.

The PD approach is not optional or elective.
Its application is necessary on every project to have a functional transportation for the long term. PD goes beyond saving money on an individual project; it aspires to build the best-performing transportation system with the money available.