  We report quantitative analysis of positive magnetoresistance (PMR) for
unidirectional-lateral-superlattice samples with relatively small periods
(a=92-184 nm) and modulation amplitudes (V_0=0.015-0.25 meV). By comparing
observed PMR's with ones calculated using experimentally obtained mobilities,
quantum mobilities, and V_0's, it is shown that contribution from streaming
orbits (SO) accounts for only small fraction of the total PMR. For small V_0,
the limiting magnetic field B_e of SO can be identified as an inflection point
of the magnetoresistance trace. The major part of PMR is ascribed to drift
velocity arising from incompleted cyclotron orbits obstructed by scatterings.
