23 C.F.R. § 630.1104
For the purposes of this subpart, the following definitions apply:
Agency means a State or local highway agency or authority that receives Federal-aid highway funding.
Exposure control measures means traffic management strategies to avoid work zone crashes involving workers and motorized traffic by eliminating or reducing traffic through the work zone, or diverting traffic away from the work space.
Federal-aid highway project means highway construction, maintenance, and utility projects funded in whole or in part with Federal-aid funds.
Motorized traffic means the motorized traveling public. This term does not include motorized construction or maintenance vehicles and equipment within the work space.
Other traffic control measures means all strategies and temporary traffic controls other than Positive Protection Devices and Exposure Control Measures, but including uniformed law enforcement officers, used to reduce the risk of work zone crashes involving motorized traffic.
Engineering study means the analysis and evaluation of available pertinent information, and the application of appropriate principles, provisions, and practices for the purpose of determining the choice and application of work zone positive protection devices, exposure control measures, or other traffic control measures to safely manage work zones.
Positive protection devices means devices that contain or redirect vehicles and meet applicable industry crashworthiness evaluation criteria. Industry crashworthiness evaluation criteria are not regulatory, and use of them is voluntary and not required by law.
23 C.F.R. §630.1104