There are two signs in the city of Sioux Falls that show the speed limit in miles per hour and kilometers per hour. In 1997, the existing West 12th Street near I-29 was reconstructed from Highway 42 into the street that it is now with curbs, gutters, and turn lanes.

Travis Dressen, who is the Sioux Falls Area Engineer with the South Dakota Department of Transportation said the dual unit sign was installed during this project in the late 90's.

"Start implementing dual unit signs to help assimilate traffic with a potential change to the metric system in the United States overall," Dressen said.

Dressen said at that time, the Federal Government was pushing to change from the English System, which is measurements like pounds and feet to the Metric System, like kilograms and kilometers. South Dakota legislators resisted this move though at the time.

"Anything that's a weight or a volume or a distance is all in english units," Dressen said. "So they would bid these projects. They would need to convert this back to english units, put their bids together and convert them back to metric."

Dressen remembers designing a bridge using the Metric System in 1999.

"There's a little bit of a learning curve and I think too, working from the contract industry, taking your english units and converting everything, it just introduces another opportunity for error," Dressen said.

The signs on West 12th Street haven't been replaced since they were originally installed.

"We try to maximize the value that we get for them," Heath Hoftiezer said, who is the principal traffic engineer for the city of Sioux Falls.

He said street signs can last about 10 to 15 years. But these are still up because they are reflective at night and look okay during the day. They are expected to last a couple more years before they go to good homes.

"A couple of people have asked about them because there's not a lot like them in our area," Hoftiezer said.

If you have any questions you'd like Vanessa Gomez to dig into, email her at vgomez@ksfy.com.