Surface Transportation Security Improvement Act of 2018 (Sec. 3) The Government Accountability Office (GAO) must evaluate the extent to which the 2016 Biennial National Strategy for Transportation Security is reflected in federal transportation security programs. (Sec. 4) This bill establishes programs and reporting requirements to identify risks to facilities, equipment, or systems used to provide public transportation (surface transportation assets). It requires the Department of Homeland Security to: develop risk-based priorities informed by an analysis of terrorist and cyber attack scenarios, submit to Congress a feasibility assessment of employing new technologies to enhance surface transportation security, disseminate best practices to protect against the threat of a vehicle-based terrorist attack, and report on threats to transportation security posed by the use of security technologies by foreign countries. (Sec. 9) The bill authorizes the Transportation Security Administration (TSA) to establish a task force to identify and develop an innovative technology to enhance transportation security. The TSA must also submit to Congress and the GAO a strategy to guide operations of surface transportation security inspectors.