Cables laid in underground ducts may experience movement in the direction o
f dominant traffic flow. This phenomenon, so called cable creepage, has bee
n known for a long time but its mechanism has not been clearly understood y
et. In this paper, an exact mechanism of creepage phenomenon is proposed in
which cable creepage is interpreted as accumulation of relative frictional
slip developed in the process of kinematic interaction between the flexibl
e cable and the duct which experiences deformation propagating into the veh
icle traffic direction. This kinematic interaction is formulated as frictio
nal contact problem and an appropriate analysis method is developed. It is
confirmed from the calculated results that creepage can occur according to
the proposed mechanism.