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SCDOT recommends retiming downtown grid, flags dozens of signals as unwarranted
Summary
SCDOT district traffic engineer Laurie Campbell told council a recent inventory of about 140 signals found many low‑volume intersections that do not meet national signal warrants; recommendations include retiming the coordinated grid, setting some signals to free‑run, and converting select low‑volume locations to stop control or pedestrian signals after stakeholder review.
Laurie Campbell, district traffic engineer for SCDOT District 1, presented a traffic‑signal analysis that included counts from roughly 140 intersections across the Columbia grid and an assessment against national warrants. She said many locations "do not meet the warrant for traffic signalization," and recommended a mix of approaches: retime the coordinated grid for major corridors and set unwarranted signals to free‑run or convert them to two‑way/all‑way stop control or pedestrian signals.
Campbell described the technical tradeoffs: coordinated timing favors the primary corridors but can leave side streets waiting in predictable windows; setting some signals to free‑run adds detection so an isolated side‑street arrival would trigger a green. She also identified cost estimates for basic upgrades at about $40,000 per intersection and noted full rebuilds would be substantially more expensive. SCDOT said removal or reconfiguration would follow a notification and trial period (signage, flashing signals for two weeks, and a 90‑day cabinet retention period before permanent removal).
Council members asked about specific locations, pedestrian priority areas, and funding sources. Staff and SCDOT agreed to produce a prioritized list for the city to review and to coordinate with neighborhood associations and emergency services before any changes.
