Charles

You need to make something that drivers don't want to run over. Rumble strips on asphalt works pretty good. We tried them in Quarter midgets I guess back in the late 60's Dad would just set the car up to carry the left front over them and it kept everybody in line. QMA's next attempt was little 6 inch tall traffic orange cones, hit a cone and you were DQ'd right on the spot. Problem was we were racing so close to the cones that sometimes we blew them over, that sure brought about a lot of off track discussion. If someone could devise a rumble strip for dirt that couldn't be dislodged by a speeding race car we would really have something. So far as close as they have got is them old Loader tires and they might be just a bit overkill.

Honest Dad himself