State Departments of Transportation permitted under the National Pollutant Discharge Elimination System's municipal separate storm sewer system program must manage their highway stormwater effectively while achieving their mission of safe transport of goods and the public. There are some key differences between how traditional MS4 permittees (cities and counties) manage stormwater and how transportation departments manage stormwater. For example, DOTs have different legal authorities to control stormwater and use mechanisms other than ordinances. In addition, their linear roadway systems often cross multiple watersheds and have limited right-of-way space. Collaboration between state DOT MS4 permittees and state NPDES permitting authorities helps identify these unique challenges and find opportunities to acknowledge and tailor the permit requirements. Join speakers from two states as we explore examples of collaborating to tailor transportation MS4 permits for highway systems and deliver better environmental results.