TPO workshop debates setting local PM3 targets; staff recommends polling before May vote

Mike Conger, TPO staff, told the TPO Technical Committee workshop that staff recommends the MPO set local targets for the Federal Highway PM3 system-performance measures covering 2026 through 2029, and proposed a staff poll to gather member preference before a May meeting.

"These measures are specific to the National Highway System," Conger said, noting the metrics apply to principal arterials and interstates in the urban area such as Kingston Pike and Alcoa Highway. He said TDOT will set statewide targets but the MPO has 180 days after TDOT to either support those statewide numbers or adopt local ones.

Why it matters: staff argued a regional target helps the MPO track local conditions and report progress in the mobility plan and TIP rather than simply deferring to a statewide number that can obscure local trends. Conger said there is no formal penalty for missing targets, but local targets create a clearer basis for discussion about investments and local priorities.

Key measures discussed: Conger reviewed four PM3 subparts that staff recommends the MPO address locally: (1) interstate travel-time reliability (80th/50th travel-time ratio), (2) truck travel-time reliability (TTTR), (3) shared subpart g measures for the urban area (peak-hour excessive delay and percent non-single-occupant-vehicle commuting), and (4) CMAQ mobile-emissions targets (subpart h) for ozone/PM2.5 counties.

On interstate reliability, Conger explained the metric: a segment is "unreliable" when any of four time periods shows an 80th/50th ratio greater than 1.5. He said the urban-area baseline for 2025 is about 83% of NHS lane-miles considered reliable and staff sees a plausible local target range of roughly 77% to 87% depending on whether the committee uses a historical-trend, baseline, or policy-driven approach.

On truck reliability, staff showed TTTR has steadily worsened since 2017 and that several segments — notably the I-40/I-75 west corridor and the Pellissippi Parkway interchange area — drive extreme unreliability in the freight metric. "If we can target the PM peak period and incident-response improvements, we could reduce those extreme values," Conger said.

On the shared congestion measures (subpart g), Conger noted peak-hour excessive delay spiked in 2025 and identified corridors contributing most to delay (I-40, Pellissippi Parkway, Illinois Avenue, Charles G. Seavers Boulevard, Alcoa Highway, and US-129 Bypass). He proposed staff use a mix of the travel-demand model and assumed reductions from planned projects (a sample 15% delay reduction from ATMS and Alcoa Highway work) to estimate candidate 2-year and 4-year targets.

On percent non-single-occupant-vehicle commuting, Conger cited ACS commuting data and the post-COVID rise in telework. He reported a 5-year ACS baseline of 23.9% and proposed using the 2024 one-year ACS value to set a target that would yield an approximate 24.6% non-SOV share for the next period.

TDOT role and timing: Conger underscored that subpart g targets are shared with TDOT and that TDOT requested the MPO's engagement on their timeline; he recommended staff coordinate with TDOT, share proposed methodologies, and return results of a staff poll at the May 12 technical committee meeting with the aim of asking the executive board to consider adoption later in May.

Committee questions and staff follow-up: Members asked whether staff would perform work in-house or contract it; Conger said the analysis would be in-house and that staff can provide segment-level breakdowns, modeled estimates, and assistance to jurisdictions pursuing SS4A or other grants. Several members requested clearer documentation of modeling assumptions, how work-from-home affects mode-share calculations, and updates on projects cited as improving measures (for example, timing and scope of Alcoa Highway and Pellissippi Parkway work).

Next steps: Conger said staff will draft recommended numeric target options, circulate them by email with supporting analysis and a Google-form poll, and report results at the May 12 meeting. "We have to set our urban-area shared target with TDOT on a compressed timeline," he said. "If the committee prefers, staff can prepare a single staff recommendation for members to react to before any formal vote."