10.8.2 One-way-street situation (inevitable effect)

The skilled person has to be free to employ the best means already available for their purposes, although the use of means leading to some expected improvements might well be patentable in relying on an additional effect, provided this involved a choice from a multiplicity of possibilities. The lack of alternatives in this respect might therefore create a "one-way-street" situation leading to predictable advantages which remained obvious in spite of the existence of some unexpected "bonus" effect (T 192/82, OJ 1984, 415; see also T 766/92, T 1936/13, T 1491/20). An additional effect achieved inevitably by the skilled person on the basis of an obvious measure without any effort on their part simply represented a bonus under EPO case law which could not substantiate inventive step, even as a surprising effect (T 506/92; see also T 431/93, T 681/94, T 985/98, T 794/01, T 688/13, T 179/18).

In T 551/89 the board stated that an effect which was to be expected as the result of an obvious measure could not contribute to recognition of the required inventive step, even if the scale of this effect was surprising to the skilled person. In this case an effect whose scale surpassed the skilled person's hopes merely represented a bonus effect following inevitably from the use of an obvious measure and obtained by the skilled person without any inventive effort on their part (see also T 506/92, T 882/94, T 696/19, T 524/18).

In T 848/94 the solution of the existing technical problem required a combination of measures (synergistic effect) that was not suggested by the prior art in such a manner that it would have been adopted by the person skilled in the art (see also T 716/07). Therefore, the person skilled in the art was not in a "one-way-situation".

In T 1713/13 the board held that a "one-way-street" situation could not be inferred as a mandatory prerequisite for the principle established in T 21/81 (see chapter I.D.10.8.1).

The board in T 1356/21 was of the view that the case law on bonus effects could not be applied to all situations where a given differentiating feature lead to (or inevitably achieved) two separable technical effects, one of which may be expected. In situations which did not qualify as a "one-way street", the board did not consider it appropriate that a crucial and unexpected technical advantage be disregarded in the assessment of inventive step as soon as any additional obvious effect was mentioned in the patent. It stated that neither T 1317/13 nor T 21/81 (see chapter I.D.10.8.1) offered a basis for an unqualified application of the bonus effect case law to any situation of plurality of technical effects without regard to their respective technical and practical importance. The board's view in this regard was in agreement with the statement in T 192/82 that the use of means leading to some expected improvements might well be patentable if relying on an additional effect, provided this involved a choice from a multiplicity of possibilities. See also T 1357/21.

In T 53/22 the board found that any additional effect stemming from the obvious combination in the case in hand (D2 in combination with common general knowledge) was a supplementary or bonus effect that could not establish an inventive step. The skilled person had very few realistic options, each of which would have occurred to them as a matter of course when they considered how to realise D2's teaching to realise a wastegate in a real turbocharger. The weighing of the pros and cons of each option depending on the circumstances and specifications was routine, here arising from straightforward practical constraints. The board distinguished the case in hand from those where there were a "multiplicity" (as in "a large number") of options (e.g. T 192/82), and also from T 848/94 because it was not argued there was a synergistic effect arising from a combination of measures.