Colorado drivers, be prepared for motorcycles to pass stopped traffic: Beginning Aug 7., motorcyclists will be allowed to lane filter. Although filtering is permitted under the new law, lane splitting remains illegal — so what’s the difference between the two? “The first thing Coloradoans need to understand is that there is a seemingly small but important difference between lane filtering and lane splitting,” said Colonel Matthew Packard, chief of the Colorado State Patrol, in a Tuesday news release.