Line cars were necessary, as compared to horse-drawn or automotive line towers, to service the overhead system on private right of way, such as the West End line along the New Basin Canal.  Here is NOPSI line car 055 at Canal Station.  The upper photo is dated May 6, 1950.  West End was just abandoned to buses a few months earlier, so the need for 055 has just about ended. — Otto Goessl photo (upper)