To boulders in the public strip or parking strip.
We know it's very aggravating when cars drive over your plantings. However, boulders don't often stop that kind of damage and they can make it worse.
A car that wanders will not be stopped by anything a gardener is able to lever into place. The car will push that rock. Then, the soil will be compacted and plants sheered off not only along the tire tracks but in the stone's track.
In addition, cars do veer off the road for legitimate reasons and in that case the verge exists as a refuge. In some cases the boulder may be ruled a hazard and the property owner held liable for damages.