A(n) ________ vehicle is a moving vehicle positioned a short distance from a moving operation to provide physical protection from traffic.

A shadow vehicle is designed to enhance safety during work zone operations by providing a moving buffer between traffic and the workers on the site. This vehicle is typically equipped with safety features such as high-visibility markings, warning lights, and sometimes crash-attenuating devices, which can reduce the severity of accidents if a collision were to occur.

The primary function of the shadow vehicle is to block or redirect traffic away from the active work area, thereby offering physical protection to personnel and equipment. Its strategic positioning ensures that if a vehicle does veer off course, it will likely encounter the shadow vehicle rather than striking workers directly.

In contrast, other types of vehicles described in the options serve different purposes—advanced warning vehicles generally alert drivers of upcoming work zones well before they reach them, barrier vehicles are often fixed installations that separate work sites from moving traffic, and FAS refers to a specific traffic management system. Therefore, the distinguishing role of the shadow vehicle as a protective measure in dynamic work environments underlines its importance in maintaining safety for both workers and motorists.