  Formal methods and supporting tools have a long record of success in the
development of safety-critical systems. However, no single tool has emerged as
the dominant solution for system design. Each tool differs from the others in
terms of the modeling language used, its verification capabilities and other
complementary features, and each development context has peculiar needs that
require different tools. This is particularly problematic for the railway
industry, in which formal methods are highly recommended by the norms, but no
actual guidance is provided for the selection of tools. To guide companies in
the selection of the most appropriate formal tools to adopt in their contexts,
a clear assessment of the features of the currently available tools is
required.
  To address this goal, this paper considers a set of 13 formal tools that have
been used for railway system design, and it presents a systematic evaluation of
such tools and a preliminary usability analysis of a subset of 7 tools,
involving railway practitioners. The results are discussed considering the most
desired aspects by industry and earlier related studies. While the focus is on
the railway domain, the overall methodology can be applied to similar contexts.
Our study thus contributes with a systematic evaluation of formal tools and it
shows that despite the poor graphical interfaces, usability and maturity of the
tools are not major problems, as claimed by contributions from the literature.
Instead, support for process integration is the most relevant obstacle for the
adoption of most of the tools.
