Unincorporated Johnson County speed limit increases

White speed limit sign (40 mph) along a rural road

On June 23, 2022, the Board of County Commissioners voted to increase speed limits on 13 segments of roads in unincorporated Johnson County, upon the recommendation of the Johnson County Sheriff’s Office and Public Works Department.

An engineering study was conducted to determine the 85th percentile speeds as well as a review of safety and sight distance issues at intersections and entrances.

The 85th percentile is simply the speed that 85% of the drivers will operate and is an important component considered when posting speed limits. The 13 segments that met the criteria for safe increases in speed limits to either 40 or 45 MPH are shown in the table below.

All the segments, with approved speed limit increases, have significant evidence of non-compliance of the existing 35 MPH speed limits by having 85th percentile speeds in the 43 to 54 MPH range. Drivers need to perceive the speed limits as credible if adequate levels of voluntary compliance are to be achieved.

Routine violation of speed limits by most drivers may breed contempt not only for speed limits but also for other traffic regulations. As a general guideline, speed limits should be set at levels that are largely self-enforcing (i.e. near the 85th percentile speed) so that law enforcement officials can concentrate their efforts on the worst offenders. Public support (i.e., willingness to obey) is closely linked with reasonableness of speed limits. 

Additionally, this is a bit counter intuitive, but studies have shown that posting the speed limit at or near the 85% percentile, groups the traffic speeds more closely together and reduces the conflicts between vehicles driving at different speeds. Issues such as the need to pass vehicles or miss-calculating the speeds of other vehicles is reduced.

Less conflict with vehicles of different speeds and better opportunity for speed enforcement should help make the segments listed below safer for drivers.

Road Segments with Speed Limit Increases

Road

To - From

Current Speed Limit

New Speed Limit

Pflumm Rd

191st St. to 199th St.

35

45

Pflumm Rd

199th St. to 207th St.

35

45

207th St.

Switzer Rd to Antioch Rd

35

45

Cedar Niles Rd

207th St. to 199th St.

35

45

207th St.

Braun St., west to Evening Star Rd

35

45

207th St.

Evening Star Rd to County Line Rd

35

45

183rd St.

Cedar Niles Rd to S-Curve before Moonlight Rd

35

45

159th St.

Gardner Rd to Waverly Rd

35

40

Moonlight Rd

119th St. to 127th St.

35

45

Moonlight Rd

127th St. to 135th St.

35

45

Sunflower Rd

215th St. to I-35

35

45

Antioch Rd

207th St. north to Overland Park City Limits

35

40

Gardner West Rd

159th St. to 151st St.

35

40

 

The new speed limits will be posted and in effect by the end of July.

Department:
Public Works
Sheriff
Category:
News
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