In field testing, or at a temporary test site not guarded by permanent fences and gates, the employer shall ensure the use of one of the following means to prevent employees without authorization from entering:
Distinctively colored safety tape supported approximately waist high with safety signs attached to it,
One or more test observers stationed so that they can monitor the entire area.
A barrier or barricade that limits access to the test area to a degree equivalent, physically and visually, to the barricade specified in paragraph (c)(3)(i) of this section, or