> For the complete documentation index, see [llms.txt](https://docs.openbrim.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.openbrim.org/templates/precast-i-girder-bridge-workflow/geometric-criteria-pig.md). # Geometric Criteria \[PIG] Requirements the bridge has to satisfy because of where it is, rather than because of what it carries. They are checked against the site geometry, not against a load combination, so they can be answered as soon as the geometry exists and long before an analysis runs. Today this section covers vertical clearance, in two objects that are used together: **Clearance Zone** * The region a clearance is measured over: the roadway, track, channel or path the structure crosses. It carries the region polygon, the surface the clearance is measured up from, and which objects are in scope. **Vertical Clearance Check** * The requirement measured over one or more zones. It finds the smallest clearance in each region, reports where that minimum occurs and what caused it, and passes or fails against the clearance you require. Splitting them this way means an interim and a final requirement over the same crossing share one region by construction, instead of relying on two rows being kept in step by hand. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.openbrim.org/templates/precast-i-girder-bridge-workflow/geometric-criteria-pig.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.