Ada County Highway District

ACHD's Road Wizard Sunday, November 24, 2019 ACHD's Road Wizard

Checking in regarding 25 mph speed limit on Catalpa; speed study on Collister

The Road Wizard Replies

Dear Road Wizard: Regarding the old; while Catalpa was still being rebuilt, with construction signs up and metal plates in the road, ACHD did a speed survey to justify a 25 MPH speed limit. I wrote in to complain at the time (as I use Catalpa regularly and wanted to still drive the 30 MPH that it used to be). Your response was that the speed survey was done, and even though the data still supported a 30 MPH limit, 25 MPH was chosen as it seemed more prudent. How well is that working? ACHD has had to go back and put in what, 7 or 8 speed humps, and quite a few of the local residents on the street have taken to putting up mini 25 MPH speed limit signs (which seem to be illegal by Idaho Code, and are within the school speed area, which gives conflicting information to the drivers during school hours). Anyway, just saying that when the Highway Department goes against its own engineering, and then contrives to use a speed survey taken during abnormal construction conditions, it tends to not work out so well.

Today's issue; I have seen the newspaper and TV stories that the Collister Drive/State Street construction is finished, and all is good, except it isn't (IMHO). Collister Drive still has five temporary traffic signs up indicating construction, increased fines, slower 25 MPH speed limit, end of construction, and one other. I was going to write to you just about the signage issue, but now I see ACHD has undertaken a traffic count/speed survey under these abnormal construction conditions with the slower speed limit sign and construction signs still up. Is ACHD attempting to manipulate the data again to leave the south end of Collister at 25 MPH? If you want to do a speed survey to prove that 25 MPH is necessary, please at least wait until all the construction is finished and the temporary signs (including the 25 MPH sign) are removed. I would hate to see ACHD having to put in more speed humps..

Anonymous

Road Wizard:

Catalpa Drive, which connects Collister Road to the "dogbone" roundabout at Hill Road, is indeed a well-studied street. ACHD conducted a speed study on Catalpa in 2010 after adding continuous sidewalk to the south side of the street. This significantly narrowed the roadway cross section causing drivers to "naturally" moderate their speeds. In turn, these geometric changes justified reducing the posted speed limit from 30 mph to 25 mph.

Catalpa Drive had speeds humps prior to the sidewalk work in 2010 concentrated around Catalpa Elementary. In 2016, the neighborhood sent requests to evaluate extending the devices and supplementing large speed hump gaps. ACHD's traffic calming policy is based on both speed and volume. Catalpa met the criteria for volume, but not speed, though a street need only meet one of the two to be eligible. The neighborhood submitted the required petition supporting installation and ACHD performed a cut-through study to determine how much non-local traffic was using the street (this is policy-driven to determine who would fund the devices--ACHD or the neighborhood). Catalpa met the cut-through percentage and ACHD installed the additional speed humps in May of 2018. The process followed all District-adopted policies.

Fast forward to your more recent concern. The data collection tubes on Collister Drive are well outside of the intersection's project limits. They are collecting post-project data based on a request from the adjacent neighborhood, following up on data collected during the construction project earlier this spring. ACHD tends to avoid collecting this information during the holiday season, so they're taking advantage of the fabulous November weather, since one never knows what January will bring. Don't be surprised if you see data collection devices at Collister Drive again next year as State Street projects continue.

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