Commissioners press for broader TIA study areas as staff explains level-of-service rules

The Planning Commission spent the first substantive portion of its June 18 meeting on an educational work session about traffic-impact analyses (TIAs), methodology for level-of-service (LOS) grading and signal timing.

A presenter (traffic consultant) explained how LOS is calculated, software used (for example, Synchro and microsimulation), and the county's adequacy thresholds: "For county roads and town center roads, the level service of C is considered, at an adequate C or better," the presenter said. The presenter described how traffic counts are gathered (manual counts; increasingly video-based counts) and how background or "no-build" conditions are projected using growth rates and ITE trip-generation rates for proposed land uses.

Commissioners questioned how the "study area" for a TIA is set and whether it should be broader in town centers. One commissioner said that for the Armoury Square and Magnolia Ridge studies the scope excluded the intersection at Stokely Road — an intersection that "really gets the most citizen complaint," the commissioner said. He urged a policy change so "all of the intersections within a town center are included in a study for a development going into that town center or near it." The consultant and public-works staff said the APFO ordinance allows the director of public works to expand study limits but that study-area decisions are made case-by-case.

Public Works Director Jared Kosko and others noted that State Highway Administration (SHA) improvements are planned for the Route 4/Stokely corridor but remain mid-design and funding-limited. Kosko said the county continues to push SHA to finish design and construction; staff described multi-phase improvements (referred to in the presentation as phases 5a/5b) that would widen approaches in places but acknowledged state funding constraints.

Commissioners also asked about signal coordination and adaptive signal technologies. Staff advised that coordinated signals (fixed offsets and timed plans) are distinct from fully adaptive systems; adaptive systems can improve nonpeak-period variability but may not provide large gains during regular peak-hour surges on heavily congested corridors.

The work session concluded with staff explaining TIA thresholds used in Calvert County: a TIA is required for proposed sites that generate 200 or more two-way trips per day or sites that meet the county's other numeric thresholds for peak-hour trips (as described by staff during the presentation). Staff urged commission members to raise study-area questions when reviewing individual TIAs so the director of public works can consider expanding scope in specific cases.