The Second Lane ProblemRoundabouts achieve safety by slowing traffic and simplifying the decisions drivers must make. The Capacity TrapThat statement reveals the hierarchy embedded in a traffic safety analysis. Only after those decisions are made does the engineer consult the design manuals to assemble what the profession defines as a “safe” design. With that requirement fixed, they are left trying to make a complicated two-lane roundabout safe through signs, markings, and driver instructions. [[divider]]Where else have you seen traffic capacity prioritized over a simpler, safer design?