Traffic study says Mid Broadwell closure would raise delays at several intersections; staff proposes targeted fixes and a pilot closure

Rob Del Ross, the city's engineering program manager, presented results of a traffic analysis focused on the Mid Broadwell closure recommended in the District Mayfield plan. The study compared 2023 baseline conditions to a 2033 build scenario that includes background growth (assumed about 1% annually), committed nearby developments and trips generated by the District's planned buildout.

The analysis covered eight intersections. Ross said some intersections (notably 1 and 3) would show poor levels of service even without the closure, while intersections 6, 7 and 8 would experience material additional delay if the Mid Broadwell segment were closed and the District were allowed to build as planned.

Staff proposed mitigation measures tied to the study's findings: an eastbound-to-southbound right-turn slip lane at the roundabout near the library (Intersection 6), and a potential small or mini-roundabout at Intersection 7 as a future project improvement. Intersection 8, which sits just over Milton's boundary in Alpharetta, would require coordination with that jurisdiction. The presentation distinguished "system improvements" (broad projects typically funded from impact-fee pools) from "project improvements" (specific mitigation that may be funded or required of individual developments).

Ross also described an operational pilot: a temporary closure of the Mid Broadwell segment over a long weekend with enhanced data-collection tools to measure real-world effects and compare them to model predictions. He recommended that any formal right-of-way abandonment process be initiated by the adjacent property owners and proceed via the city's abandonment code.

Council did not vote on closure or mitigation steps at the work session; staff said the findings should guide long-range capital planning and that developer agreements may be appropriate if future project-level mitigation is required.