  A measurement of the azimuthal asymmetry in dihadron production in
deep-inelastic scattering of muons on transversely polarised proton (NH$_{3}$)
targets are presented. They provide independent access to the transversity
distribution functions through the measurement of the Collins asymmetry in
single hadron production. The data were taken in the year $2010$ with the
COMPASS spectrometer using a $160\,\mbox{GeV}/c$ muon beam of the CERN SPS,
increasing by a factor of about three the available statistics of the
previously published data taken in the year $2007$. The measured sizeable
asymmetry is in good agreement with the published data. An approximate equality
of the Collins asymmetry and the dihadron asymmetry is observed, suggesting a
common physical mechanism in the underlying fragmentation.
