Tesla, Inc. found that some of its Model Year 2012-2020 cars don't fully meet a federal safety standard about how speed is displayed. Tesla reported this issue and asked the National Highway Traffic Safety Administration (NHTSA) for a decision that this does not affect vehicle safety significantly. Tesla explained that while drivers can switch the speed display between miles per hour and kilometers per hour, the default is miles per hour, which is common in the U.S. They also highlighted efforts to update cars to show speed correctly. NHTSA has received this petition but has not yet made a decision.
Simple Explanation
Tesla noticed that some car speed displays aren't following a certain rule perfectly, and they asked the government to decide if this is a big problem for safety. They're saying it's not a big deal because drivers in the U.S. usually see speed in miles per hour.