It was a vehicle of necessity- Explain

The Ox by H.E. Bates is a short story not about the beast of burden, the ox but about the deep tragedy of Mrs. Thurlow. Here 'it' refers to Mrs. Thurlow's sole companion bicycle. The significance of the bicycle in Mrs. Thurlow's life and drudgery is here indicated.

            Mrs. Thurlow, the main character of the story, worked hard from early morning to the  midnight to save her family of her husband and two sons. In her life of unbroken drudgery, her unfailing companion was her bicycle as "her relationship to it was that of a beast to a cart." The bicycle was old, rusty, hardly cleaned or repaired, but very much essential to her life. The bicycle was always loaded, but could never be ridden. She used to carry grey bundle of cloths, oilcans, sacks, cabbages, bundle of old newspapers, boughs of wind-blown woods, and her bags of chicken food in her 'rusty' bicycle. We use the bicycle for our comfort, for our luxury, but Mrs. Thurlow used it to serve her necessity, the bicycle was no element of luxury to her.

             This line signifies much truth of Mrs. Thirlow's life of drudgery.  The expression 'vehicle of necessity' is deeply meaningful in the assesment of the nature of Mrs. Thurlow's life of drudgery. Bates emphasizes here Mrs. Thurlow's approach to her bicycle.