What: straight-line diagrams — linear, milepost-referenced drawings of features along State Highway System roadways. The online GIS app (slogis.fdot.gov) searches by district, county, roadway ID, or a map click; the SLD Handbook (April 2023 edition #status/verify) is the legend for the symbols and abbreviations.
Why: the fastest way to get features tied to mileposts on a state road — which is how FDOT references crash locations, project limits, and RCI data.
When: converting crash mileposts to real locations (and back), corridor feature inventory, confirming begin/end limits, cross-checking RCI.
No login; diagrams download as PDFs. Gotcha: diagram vintages vary by roadway — check the date block and verify anything decision-critical against current aerials or the field.
Tip
Keep the roadway ID (8-digit) from the SLD — it’s the key that joins FTO stations, RCI extracts, and crash records to the same corridor.
See also: FDOT Open Data Hub · How to Summarize 5-Year Crash Data · Florida Traffic Online (FTO)