Drag the span slider. Each type grows toward full size across its economical span band and shrinks (then dims) outside it.
How size works. Within a type's economical span range, the drawing holds maximum size across the central 20–80% band and tapers over the outer 0–20% / 80–100%. Out of range it sits small and greyed. Sizing is a suitability cue, not a precise design check.
Ranges overlap on purpose — at the boundaries the decision is driven by constraints the chart cannot see: navigation clearance, pier locations you are not allowed to use, seismicity, and what local contractors have actually built before. The cheapest bridge type is usually the one the region has experience erecting.
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