SIOUX FALLS, S.D. (KELO) – As the City of Sioux Falls grows, so too do its traffic woes, and high among those are drivers who take to the roads at speed. “We would like you to slow down,” said Lieutenant Andrew Siebenborn with the Sioux Falls Police Department (SFPD). He says speed and alcohol are the two biggest killers when it comes to traffic in Sioux Falls.