Question: how long are the broken white painted stripes in the middle of the roadway?

The answer is 10 feet. That is the government rule for each road, roadway, and provincial street in the United States, where dashed lines isolate movement paths or show where passing is permitted. The investigation, published in the journal Perception & Psychophysics, found when the students were standing some separation far from real 10-foot lines or riding by them in an auto, they judged the size to be the 2 feet.

That is true , instead try to have a sit down talk with them