How far from a street should a crepe myrtle be planted?
Certified GKH Gardening Expert
I wouldn't worry about the roots being invasive. This article will explain: https://www.gardeningknowhow.com/ornamental/trees/crepe-myrtle/crepe-myrtle-root-system.htm
You will be limited by the size of the shrub you choose. Many will get to between 5 and 10 feet wide. If you are planting at least 10 feet away, then you can be sure that it will not obstruct the road.
Here is an article that will help you with the care of the shrub: https://www.gardeningknowhow.com/ornamental/trees/crepe-myrtle/crepe-myrtle-care.htm