Nationwide Dig Once Act of 2020 This bill directs the Department of Transportation (DOT) to facilitate the installation of broadband infrastructure in each state. DOT must ensure that each state that receives funding under the federal-aid highway program meets certain requirements, including to (1) identify a broadband coordinator that is responsible for facilitating the broadband infrastructure right-of-way efforts within the state; (2) establish a process to notify broadband providers of highway construction that may present opportunities for coordinating installation of broadband infrastructure; and (3) install broadband conduit (conduit or inner duct for fiber optic cables or wireless facilities that support broadband service) as part of a federally funded highway construction project, unless a broadband provider has committed to deploy the conduit or broadband infrastructure as part of such project. DOT must issue guidance for best practices related to the installation of broadband conduit and of conduit and similar infrastructure for intelligent transportation systems that may utilize the broadband conduit. A state may waive the required installation of broadband conduit if it makes certain determinations, including if broadband infrastructure, terrestrial broadband infrastructure, aerial broadband fiber cables, or broadband conduit is present near a majority of the length of the federal highway construction project. The bill establishes a Dig Once Funding Task Force to (1) estimate the annual cost for implementing and administering a nationwide dig once requirement, and (2) propose and evaluate options for funding such a requirement.