From the indication of these two articles which make no reference to any male operator, I would guess that Otto turned the car over to his wife and got her the authority to also run over the Silverton Branch.
Was there even room for a twelfth person?
Oct 1, 1910s Silverton Standard
Thursday afternoon, Mrs. Otto Mears treated a number of her lady friends to a delightful ride in her railroad automobile from Silverton to Eureka and return. It was a unique as well as a beautiful arranged affair and those who enjoyed the trip with their pleasing hostess were Mesdames B. B. Allen, F. B. Brown, A. A. Brown, D. J. Maxwell, Robert Pearson, Frank Grimes, W. W. Grimes. F. L. Ross, W. N. Searcy, and Miss Marguerite Slattery.
Oct 15, 1910 Silverton Standard
A jolly party of Silvertonites, composed of Mrs. Otto Mears, Mrs. J. R. Pitcher, Mrs. J. D. Maxwell and Mrs. W. H. Crooke enjoyed a most pleasurable trip down the canon of the Animas last Wednesday morning in Mr. Mears’ railroad automobile as far as Hermosa, where they were met by Mrs. Rasmus Hanson with whom they spent the day in the fullest enjoyment of her charming hospitality, returning in the auto in the evening.