Subscribe for 33¢ / day
Kilometers per hour speed limit signs

Signs displaying the speed limit in both miles and kilometers per hour are shown along southbound Interstate 29, north of the McCook Lake interchange, in April. Motorists would be able to travel up to 75 mph legally on designated interstate highways in Iowa under a proposal getting revved up in the Iowa Senate.

We're defining Siouxland in 150 icons. The daily series began Aug. 17. Follow along at

NORTH SIOUX CITY | Well, that's weird. Three roadside signs remain in Union County, S.D.,  from an aborted nationwide campaign to adopt the metric system.

President George H.W. Bush in the 1990s called for interstate highways to display speed limits not only in miles per hour but also in kilometers per hour. The plan died on the vine, yet the signs remain.

The state first began placing signs with both mph and kph after Bush signed Executive Order 12770 in July 1991.

South Dakota officials decided to get on board with some 1990s metric signage, but the federal push soon languished. The few signs left along South Dakota interstates with dual markings still stand because they haven't needed to be replaced in the intervening two decades.

On northbound Interstate 29, just north of the mile marker 4 exit for McCook Lake, a sign shows the speed limit at 75 mph as well as 120 kph. A kilometer is six-tenths of a mile.

On the southbound side of the highway near the same exit, two signs inform motorists that the speed limit has dropped to 65 mph and 105 kph.

Signs with speeds in both measurements are relics rarely seen in the United States. There are some in Alabama, California, Florida and Washington.

Some Siouxland people find the signs a curiosity, while others admit they've never picked up on the extra speed designation on the signs.

Eventually, they will go away, but for now be sure to notice the peculiar speed signs when driving by.


County and education reporter

Load comments