Knox County TPO staff seek local performance targets for federal PM3 measures, urge coordination with TDOT

Mike Conger, TPO staff, told a Knox County‑area Transportation Planning Organization technical committee workshop that staff recommends establishing local targets for the federal PM3 performance measures covering system performance, reliability, congestion delay and on‑road emissions for the 2026–2029 performance period. "We're starting the third four‑year performance period for these. This performance period will run from 2026 through 2029," he said.

The proposal responds in part to a scheduling constraint: TDOT is expected to set statewide targets by Oct. 1, and MPO/TPOs then have 180 days to support those targets or set their own. Subpart G (traffic congestion) includes a shared urban‑area excessive‑delay target that staff said should be coordinated closely with TDOT. Conger said staff can pull the necessary data and host a polling process to gather member input before a May discussion and possible board action.

Why it matters: the PM3 measures are codified in federal rule (23 CFR part 490) and inform how federal highway programs track system performance. While there are no federal penalties for missing targets, local targets would let the TPO report annually and discuss how TIP investments affect regional conditions, staff said. "The biggest benefit is bringing this information to light and discussing it," Conger said. He recommended a pragmatic, baseline‑driven approach for most measures while noting safety targets earlier in the year used aspirational goals tied to longer‑term regional safety plans.

Key measures and staff observations

- Interstate travel‑time reliability (subpart E): defined as the ratio of the 80th‑percentile to the 50th‑percentile travel time (threshold 1.5). Staff reported a 2025 baseline of about 83% of the interstate NHS network considered reliable, but noted a declining trend since 2020 and identified I‑40/I‑75 west of Knoxville and the I‑40/I‑640 interchange as primary trouble spots. Staff described a potential local target range of roughly 77–87 percent depending on chosen philosophy and segment‑level fixes.

- Truck travel time reliability (TTTR) and non‑interstate NHS (subpart F): TTTR (95th/50th percentile for trucks) has risen since 2017 and shows extreme values at some interchange segments (staff cited values above 6.0 in the worst locations near the Pellissippi Parkway interchange). Staff said targeted PM‑period incident response and corridor projects could reduce the worst outliers.

- Peak‑hour excessive delay (subpart G): an urban‑area, population‑normalized measure that staff said spiked to about 14 hours per capita in 2025. Top contributing corridors included I‑40, Pellissippi Parkway, I‑140/Illinois Avenue and Alcoa Highway. Staff modeled a scenario where ATMS and corridor projects could reduce delay and noted the TPO must coordinate this shared urban target with TDOT.

- Percent non‑single‑occupant vehicle (non‑SOV) mode share: measured from American Community Survey commuter data as a proxy for broader travel demand reduction. The five‑year ACS baseline was 23.9 percent; staff proposed using the 2024 one‑year ACS value to set two‑ and four‑year targets (a 4‑year target example of 24.6 percent was presented).

- CMAQ emissions (subpart H): these targets are estimated from selected projects in the ozone and PM2.5 nonattainment/maintenance areas (Knox County, Blount County, Loudon County and small parts of Anderson and Roane counties). Staff said three projects are tentatively selected in the TIP and that TDOT coordination is needed to finalize baselines and emission estimates.

Member discussion and next steps

Committee members asked about staff capacity and whether target setting would be done in‑house; staff said the analysis will be completed in‑house and emphasized the value of a regional dashboard to track progress. Members also discussed the limits of local control, asking how the TPO could influence TDOT project selection; staff recommended using the local target work to inform conversation with TDOT and advocate for regionally important projects.

Conger proposed staff distribute a polling form with staff recommendations for each measure, compile results and return to the technical committee on May 12 and to the executive board on May 27 for potential action. "We will report back on how we're trending and what our condition is," he said. The workshop did not adopt numeric targets; staff will return with a staff recommendation grounded in local data and member input.

Ending

No votes were taken at the workshop. Staff will circulate follow‑up materials and a polling form, continue coordination with TDOT on the shared subpart G target, and present a recommendation at the May technical committee meeting.