A jointing method combining slide-fitting with tension-induced compression is presented. It eliminates the "analysis black box" at each node of a timber structure. Mathematical and computational modeling is further enhanced by the use of small diameter timber (SDT), due to its more predictable natural growthring structure. This is the core concept of the LPSA (light prestressed segmented arch) structural system as applied to timber-in-the-round. It represents a significant leap forward in the sustainable use of timber in construction, offering a sustainable alternative to steel and concrete, especially for bridges. The slidefitting jointing mechanism produces a unique property of harmless distortion energy dissipation via internal rigid-body motion. Therefore, LPSA structures have inherent resistance to the actions of earthquakes, hurricanes and flooding. The LPSA structural system outlines a framework for an urgently needed research, design and innovation field of sustainable engineering, in a world on the verge of environmental instability. SDT is a vast, untapped, sustainable resource. Its use as a premium construction material could provide a recipe for saving what remains of the world's forests and for profitable sustainable development. Two 19,5 m LPSA bridges have recently been constructed, using black locust (Robinia pseudoacacia) SDT. This is a least desirable but decay-resistant species with twoto-three times the crushing strength of concrete.