Background: One of the current trends of modern transport systems development process is innovative technologies application aimed to rational use of resources, which is confirmed by the development of high-speed rail supposing to reduce travel time costs. The world practice of high-speed railway projects implementation verifies variety of transport availability influences on social and economic sphere that allows to consider HSR not only as the transport innovation defining competitiveness of railway transport, but also as the economic stimulation tool for territory development. Aim: to substantiate the formation mechanism of external effects from high-speed rail transport projects implementation. Methods: the study was conducted by means of scientific methods such as the systematic method, comparative analysis, analogy, generalization and abstraction, synthesis, induction. Results: the formation mechanism of external effects from the transport accessibility improving caused by HSR projects implementation was specified, which allows considering HSR projects as a tool for economic development. The dual nature of the relationship between the high-speed rail efficiency, which ensure the external effects formation, and integration transport processes that affect transport accessibility was revealed.