  First, this paper proposes the definition of directional congestion in
certain input and output directions in the framework of data envelopment
analysis (DEA). Second, two methods from different viewpoints are also proposed
to estimate the directional congestion in a DEA framework. Third, we address
the relations among directional congestion and classic congestion and strong
(weak) congestion. Finally, we present a case study investigating the analysis
of the research institutes in the Chinese Academy of Sciences (CAS) to
demonstrate the applicability and usefulness of the methods developed in this
paper.
