Zipping along the higway, coming out of a curve, you suddenly see vehicles going 30 merge from a very short on-ramp merge into dense 70 mph traffic. At the same time, cars cut across all lanes to make it to the off-ramp that comes right AFTER the on-ramp. I think it's easy to see how cars, criss-crossing each other, especially while accelerating or decelerating, isn't exactly a good idea. The whole on/off-ramp combo is maybe 50 yards long. Sometimes, a black and white sits there, hoping to slow down people. Problem is, due to the curve and a view-obstructing overpass you can't even see the on/off-ramp, or the cop, until you are only 3 seconds away from it. That's one crazy spot in Marin county.