It depicts the unpredictability of journey, with an unknown location.
This is strongy suggested with the use of personification, "While time ran ahead/ Along glistening tracks of steel."
A sinister destination is implied from the verb "glistening" and the simile, "Like cattle bought for slaughter."
The allusion to "eyesight" (Cutting us off from the space of eyesight) suggests that their metaphorical span of vision is anything but broad.
It also shows the extent of the consequences that can be had on partakers of the journey. The "empty streets" having "benevolence" implies that there is no one there to view their confusion and misery.
"Watching pigeons/ That watched them," connotes the peculiarity of the immigrants in unknown territory through incongruous imagery.