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Linear induction motors (l.i.ms) have many possible applications, ranging from low-speed cranes to high-speed ground-vehicle propulsion. However, in average and high-speed l.i.ms, the end effects cause considerable deterioration in the performance in low-slip regions. The paper introduces the concept of realistic goodness factor GR, which takes into account by appropriate coefficients the airgap leakage, secondary sheet skin effect and transverse edge effects. Approximations involved in obtaining GR are discussed and essentially a one-dimensional analysis is used. It is shown that the end-effect influence can be expressed as a function of GR, slip and the number of poles. An optimum goodness-factor criterion Go to aid an optimum l.i.m. design is proposed. It is demonstrated that Go can be achieved in practice, and leads to a good-performance, low-weight l.i.m. Numerical results based on a full-size existing l.i.m. test vehicle are given.