In the Canadian Forces, somebody who starts making dumb off the cuff suggestions that are not related to the matter at hand...Gets told to "Stay in your own lane ". Meaning tend to your knitting, and muckle down on the job to be done.
A second way that phrase can be used is in oval track stock car racing, where a slow runner who is blocking the faster cars, will get the "passing flag " waved at them by the starter, to move over "And stay in your lane " until the fast cars have passed him. A final use of the expression is in the winter, when snow machines are out on the trails going through the bush. Trails are two way paths but in some places the trail is very narrow, so "staying in your own lane " is very important, to avoid head on collisions.
For those Americans who live in the deep south and never see snow, I will mention that here in Canada there are thousands of miles of snow machine trails that criss cross the forests. In northern Ontario, it is possible to travel hundreds of miles on the trails between towns. Group travel on snow machines is a very popular winter time activity in Canada. JIM.