keeping track of a driver's hos requires the use of a log book. a truck driver's log book is a legally defined form containing a grid outlining the 24-hour day into 15-minute increments. the driver must specify where and when he/she stopped between driving shifts, what duties were performed (if any), along with the driver's name, truck number, company info, and other information. the driver must also present his or her log book to authorities upon request, for inspection. in lieu of a log book, a motor carrier may substitute an electronic on-board recorder to record the driver's hours.