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Needham working group hears Apex traffic update; model predicts limited diversion, local businesses raise concerns
Summary
Apex told Needham’s Envision Needham Center Project Working Group that updated VISM modeling incorporating diverted trips and new signal counts predicts modest diversion (roughly 0–11% depending on scenario) and most local routes would see under one minute of added delay; business owners warned diverted vehicles could reduce retail visits.
Apex consultants presented an updated traffic analysis to the Envision Needham Center Project Working Group on Jan. 21, saying the firm’s stochastic VISM model — run with September 2025 counts and calibrated Replica origin/destination data — now incorporates diverted trips and new signal‑collected counts. "We're using the traffic counts collected in September 2025," Margo Spiller of Apex said, describing the data and modeling approach.
The model examined three peak periods (AM peak, school dismissal and PM peak) and evaluated two build scenarios: a 2‑lane alternative and a 2‑lane alternative with separate left‑turn lanes. Apex said it used a pragmatic rule that any maneuver showing more than a 2–3 minute increase in travel time would likely cause some motorists to seek alternate routes; those trips were recorded as diverted in repeated VISM simulations. "What we have identified is a 2 to 3 minute threshold of increased travel time," Spiller said.
Under the 2‑lane alternative, Apex reported diversion peaks of roughly 120 vehicles per hour in the morning and up to 200 vehicles per hour…
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