Regional safety presenters urge clearer guidance on left‑turn signal phasing to cut severe crashes

Catherine (staff member) opened the webinar by saying left turns at signalized intersections are a persistent contributor to severe crashes in the Denver region and urged local agencies to consider clearer decision rules. “11 of all fatal and severe crashes in the Denver region involve a vehicle making a left turn at a signalized intersection,” she said. Presenters from the consulting firm Consort described work they completed for CDOT to turn an earlier memo into a more detailed guidance flowchart that local regions can use when evaluating left‑turn phasing.

The guidance packages a two‑stage flowchart. Diana McHale (Consort) and George Shackle (Consort) said the first stage applies to nearly every intersection and checks safety and geometric criteria — sight distance, speed limits, lane configuration and pedestrian/cyclist interactions — to indicate whether an intersection should be considered for protected‑only phasing. The second stage addresses existing signalized intersections and adds operational criteria such as cross‑product crash calculations and delay thresholds that can point toward protected‑permissive timing.

Consultants summarized empirical findings…