We don't have rules specifically about car sales lots. However, anytime a commercial use abuts or is adjacent to a residential use, we require a screening & buffering treatment. They can do a 6 foot tall masonry wall, a tubular steel or wrought iron fence with masonry columns and landscaping, or (with commission approval) an all landscaping screen or something else (berms, etc.). They have to provide a 10 foot wide landscape area on their side of the property line (no pavement), with at least 1 large tree (3 inch caliper) for every forty feet of adjacency. With our architectural standards, they get extra points for larger trees (4 inches) or more of them (1 per 30 feet). We also have a maximum amount of foot candles that can be measured at the line between commercial and residential districts.
If you didn't want this to apply to all areas, you could build it into your "Highway Commercial" district, or whatever you call it.
Good luck!