City staff briefs planning commission on developer workshop and how traffic impact analyses are required

Interim City Engineer Mike Garman told the Planning and Zoning Commission on Feb. 12, 2025 that the city’s street regulations set the thresholds and level of detail required for a traffic impact analysis (TIA) and that the city uses the Institute of Transportation Engineers (ITE) trip generation manual and the Manual on Uniform Traffic Control Devices (MUTCD) to make those determinations. "What's required for a TIA is spelled out in our street regulations," Garman said, and he added, "if it's anything less than 200 peak hour trips, we don't require traffic impact analysis."

Garman outlined how trip-generation estimates from the ITE manual are used to calculate new peak-hour trip ends and gave examples: a 96-unit single-family subdivision produces roughly 75 AM peak-hour and 100 PM peak-hour new trip ends — below the city's 200-trip threshold and therefore would not require a TIA; a 232-unit subdivision would generate about 227 PM peak-hour new trip ends and would require a TIA under the city standard.

Garman reviewed MUTCD signal warrants commonly applied in Kingman — vehicular volume, pedestrian volume and crash experience — and noted that the MUTCD is a federal standard enforced locally to determine when stop signs or traffic signals are warranted. He also summarized school-route planning requirements: school route plans prepared by school officials, law enforcement and traffic engineers should document pedestrian routes, marked crosswalks and crossing guards for designated school crossings.

Earlier in the meeting, Development Services staff (Jason) briefed the commission on the department’s first-quarter developer workshop. Jason said the Jan. 29 workshop was attended by about five development entities, several council members and a couple of planning commissioners, and that staff discussed zoning-code updates, a planned update to the city subdivision ordinance, drainage manual revisions and permitting-system improvements. Staff said the next workshop is targeted for April 2025.

Commissioners pressed staff on phased subdivisions and cumulative traffic impacts. Garman said the city reviews subdivisions "in totality" when they are not already approved in an earlier plat and that if a subdivision is approved and later built in phases, the traffic decision would have been considered with the original approval. Commissioners also raised the relationship between TIA findings and street widths; staff pointed to the city’s street regulations and traffic master plan as the documents that govern required street cross-sections and where collector and arterial connections should be located.

Commissioners asked about school zones along Bank Street. Staff said they have been working with the Kingman Unified School District and that some school-zone rules are detailed in state supplements to the MUTCD. Assistant Public Works Director Jack Plottey, who joined the discussion, said staff would continue coordinating with schools and law enforcement on school-route planning and crossings.

Garman suggested the commission could consider reviewing the city’s 200-peak-trip threshold if members are concerned developments are generating traffic that "get under the radar" because they fall below the current requirement.