The principles and practice of routing are well established and well known today, 12 years after the conception and 5 years after the introduction of the idea in Western European waters. It is the accelerated rate of change that makes it necessary to review the present situation and consider some permanent form of review, and plan development and improvement when necessary. The changes are technological, social, political and economic. The technological changes seem predictable, are measurable and can be caught in mathematical models, and consequently are ideally suitable for modern research techniques. The econometrist endeavours to do the same with economic changes. The much later application of mathematics to often empirical data is however bound to render results with greater variance in the answers.