What characteristic defines the layout of a conventional animal facility?

In a conventional animal facility, the layout often lacks specialized design provisions for separating clean and dirty traffic. This means that there may not be distinct zones or pathways designated for clean handling and dirty materials, which could lead to increased risks of contamination and stress for the animals. Such a design is typically less effective in maintaining sterility and proper hygiene, which are critical for animal welfare and the integrity of research.

In contrast, facilities designed with animal welfare in mind generally incorporate features that distinctly manage clean and dirty areas to reduce disease transmission and ensure a more sanitary environment. The other options suggest positive characteristics or improvements that are not typically emphasized in a conventional setup. Therefore, the defining characteristic for a conventional animal facility is indeed the absence of special design provisions for managing clean and dirty traffic effectively.