Legal Definitions - middle-of-the-road test

The middle-of-the-road test is a term used in U.S. patent law, also known as the Hydraflow test, which originated from the case In re Hydraflow (1985). This test provides a structured framework for courts and patent examiners to determine whether an invention is "obvious" and therefore not eligible for a patent. Under U.S. patent law, an invention cannot be patented if it would have been obvious at the time it was made to a person having ordinary skill in the relevant art (PHOSITA).

The "middle-of-the-road" designation reflects its balanced approach. It avoids both an overly strict interpretation that would make almost all inventions obvious (because most build on existing knowledge) and an overly lenient interpretation that would allow patents for trivial combinations. Instead, it guides the assessment by considering:

• What the existing body of knowledge (prior art) teaches.
• Whether there was a clear reason or motivation to combine known elements in the way the inventor did.
• Whether a person of ordinary skill in the art would have had a reasonable expectation of success in achieving the invention by combining those elements.

Here are some examples illustrating the middle-of-the-road test:

• Combining Known Software Modules:

  Imagine a software developer creates a new application by integrating a widely available open-source mapping module with a standard user authentication system. Both components are well-known and have established methods for integration. The middle-of-the-road test would ask if a software engineer with ordinary skills would have been motivated to combine these specific modules to create this particular application, and if the outcome of such a combination would have been reasonably predictable. If the combination simply performs the expected functions of its individual parts without any surprising new functionality or unexpected synergy, a patent examiner applying this test might find the invention obvious, as it represents a straightforward integration of known elements.

• Adding a Standard Feature to an Existing Product:

  Consider a company that designs a new type of ergonomic office chair. Their innovation involves adding a commonly available, adjustable lumbar support mechanism, which is already used in many other chairs, to their unique chair frame. The middle-of-the-road test would evaluate whether a furniture designer (a person of ordinary skill in the art) would have been motivated to incorporate such a known lumbar support into an office chair design to improve comfort, and if the successful integration and resulting comfort improvement were reasonably expected. If the addition is a predictable solution to a known problem (lack of lumbar support) using a known component, the invention might be deemed obvious.

• Developing a New Cleaning Solution:

  Suppose a chemist develops a new household cleaning solution by mixing two well-known chemical compounds, Compound A (known for its degreasing properties) and Compound B (known for its disinfectant properties). Both compounds are commercially available, and their individual functions are widely understood. The middle-of-the-road test would assess if a chemist of ordinary skill would have been motivated to combine these two specific compounds to create a dual-action degreasing and disinfecting cleaner, and if the resulting combined properties were reasonably predictable based on the known characteristics of A and B. If the new solution merely exhibits the sum of the known properties of its components without any unexpected synergistic effect, the invention could be considered obvious under this test.