Transportation officials in Massachusetts recently announced the state will halt the use of a widely-used guardrail end terminal while it conducts "additional research," days after an ABC News investigation looked into allegations that a small design change turned the metal safety structures potentially deadly. "In light of a recent report raising questions about the performance of a specific guardrail end terminal, MassDOT [Massachusetts Department of Transportation] has taken initial steps to halt the use of that end terminal while the agency conducts additional research," MassDOT said in an email to ABC News Wednesday.