Speed study finds 85th-percentile speeds near 50 mph on Umtanim Road; board directs staff to set public hearing and broaden study area

Cameron Curtis with Public Works presented the results of a speed study on Umtanim Road and asked the board to direct staff to set a public hearing to receive the engineer's report on a requested speed reduction.

Curtis described an initial screening that scored the request 37 out of a possible 60 points (the county's threshold for a study is 35 points) and said staff deployed traffic tubes at two locations: one just outside the city limits at milepost 1.13 and a second site outside the school zone at milepost 1.79. The traffic-tube results recorded 85th-percentile speeds of 49.4 and 49.7 miles per hour at the two locations, and measured average daily traffic (ADT) counts of 2,747 vehicles (28% truck traffic noted in that location's counts) and 1,188 vehicles (about 41% truck traffic at the second location), respectively.

Curtis reported seven reported accidents in the last five years on the corridor (mostly weather- or animal-related) and noted unusually strong community outreach including the school district, students, businesses, volunteer groups and residents. He said that while federal guidance has historically emphasized the 85th-percentile speed, recent FHWA guidance includes additional considerations such as land use and community support that could justify a lower posted speed.

Curtis also said staff had received an informal request to consider lowering the posted speed across a longer stretch of road beyond the original city-limits-to-Manhattach segment, and recommended the board direct staff to expand the study area and set a public hearing on the engineer's report. Commissioners directed staff to proceed with setting the public hearing and to expand the scope of the engineering report to include the longer corridor for public review.