Practical Design

[jakeroot]

I see this term popping up a lot lately. Here's how WSDOT defines it, per chapter 1100 of Washington's Design Manual:

Practical design is an approach to making project decisions that focuses on the specific problem the project intends to address. This performance-based approach looks for lower-cost solutions that meet outcomes that WSDOT, partnering agencies, communities, and stakeholders have identified. Practical design is a fundamental component to the Vision, Mission, Values, Goals, and Reforms identified in Results WSDOT, the department's Strategic Plan. The primary objectives of the practical design approach are: (1) focusing on project need, and (2) seeking the most reasonable low-cost solution to meet that need.

Practical design allows flexibility and freedom to innovate, and considers incremental solutions to address uncertainties in future scenarios. Practical design can be applied at all phases of project development; however, it is most effective at the scoping level or earlier, where key decisions are made as to what design controls and elements are affected by alternatives and how they can best be configured to meet the project and contextual needs.

With practical design, decision-making focuses on the maximum benefit to the system, rather than the maximum benefit to the project. Practitioners are to "design up,"  starting with minimal design element dimensions and increasing those values until acceptable cost-effective performance is obtained. Focusing on the specific project need minimizes the scope of work for each project so that systemwide needs can be optimized through individual project savings.

From some of my discussions with engineers, this basically translates into smaller, cheaper projects, that can be completed quicker. For example, two new freeways planned for the Seattle area will be built in two phases. Phase 1 for both projects is to, effectively, build a 2+1 road, with basic interchanges. Phase 2 expands both freeways to 3+3, more or less, and builds the final interchange designs (a stack for one interchange instead of a half diamond -- see what I mean when I say basic?).

For all intents and purposes, practical design doesn't seem to be the result of a smarter construction method, but rather, tighter budgets. From a practical perspective, it makes more sense to build the whole project all in one go, so as to minimize long-term construction interfering with the local economy. But, because money doesn't always roll in at once, you sometimes have to phase that construction into multiple phases, lasting a decade or more. And to make this concept slightly more appealing, the term "practical design" was adopted.

So, should I take off my tin foil hat? Is practical design entirely the result of budget constraints? Is it actually a smarter way to build big projects?

One state that doesn't seem to build roads in this "practical" manner is Arizona, which has been building freeways in their ultimate configurations for decades. Though, I don't think this is a surprise, given how well funded their road are (hence my suspicion that practical design is 100% the result of tight-ish budgets).

[hbelkins]

I've heard the term used to describe "dumbing down" projects in ways such as lowering the design speed, reducing shoulder widths, etc. For instance, in Kentucky, a rural two-lane road that normally would be built with a 65 mph design speed, 10-foot paved shoulders and 12-foot lanes might instead be built to a 55 mph design speed with 3-foot shoulders and 11-foot lanes.

[pianocello]

I've heard the term used to describe "dumbing down" projects in ways such as lowering the design speed, reducing shoulder widths, etc. For instance, in Kentucky, a rural two-lane road that normally would be built with a 65 mph design speed, 10-foot paved shoulders and 12-foot lanes might instead be built to a 55 mph design speed with 3-foot shoulders and 11-foot lanes.

Not that that's necessarily a bad thing. I heard of practical design in this context in Indiana, where they reduced the width of the road (not sure about the design speed) when they reconstructed it because it was a 10-mile stretch of straight flat road with a virtually infinite sight line. The motive for this wasn't entirely due to funding IIRC; it was just that after thinking about the geometry and traffic of that road, they determined that building a (relatively) giant facility all the way to INDOT standards was unnecessary.

As far as building in phases goes for freeways, maybe the building of phase 2 would be dependent on the success of phase 1 (i.e. if it's determined after one phase that that's all they need, they'll relocate the funds they previously earmarked for the second phase)? That, or the basic interchanges were meant to be a temporary thing from the start.

(edited to add the second paragraph)