Research conclusions: The 30 cm thick Rayleigh wave weighted average method retains the feature of testing in-situ original data, and the comparative evaluation to the transition section is easily to be made with this method. The statistics of the tested data indicates that the change regulation of the wave velocity of the subgrade in the transition section along the depth is of first decrease and then increase. The bearing capacity of the 0-1.2 m deep subgrade can not meet the requirements of raising speed, so this subgrade needs to be reinforced severely. The bearing capacity of the half of the 1.2-2.4 m deep subgrade can meet the requirement, so the targeted reinforcement should be conducted. The bearing capacity of 2.5 m below subgrade (embankment) can meet the almost all requirement, so it needs no reinforcement.