Given the following chart of jobs assigned with Johnson's rule suppose that all the jobs (A, B, C, etc) could be evenly divided into two tasks (such as A1 and A2, B1 and B2, etc). Suppose job D is split into two equivalently sized sections, D1 and D2, each with a body work time of 1.5 hours and a paint time of 2 hours (D1 and D2 sum to 3 hours of body work and 4 hours of paint which is equivalent to D). How much is makespan reduced by this splitting of D?

Job D1 could now start paint at t = 1.5 and would finish at t = 3.5 Job D2 could start paint at t = 3, however paint is occupied until t = 3.5. Thus D2 will start paint at t = 3.5 and finish at t = 5.5. However, this does nothing to save makespan time because C will not start on paint until t = 10. The only effect splitting had is to change the idle time for paint from t = 0 through t = 3 and t = 7 to t = 10 into two uneven time slots of t = 0 to t = 1.5 and t = 5.5 to t = 10.