This sign says: Beginning in 6 km, motorcycle traffic is not allowed on the "Look Into The Land" stretch of (Highway) L124 from first April to first November on weekends and holidays.
Located in the Black Forest south of Frieburg, it used to be a road-racing track until 1989, but I guess the moto-community didn't get the memo and kept on racing. And crashing. The closure is due to the high rate of accidents there in recent years. I went on a Friday and lived to tell the tale. Come visit, and I'll take you. Meantime, whet your appetite here: http://www.youtube.com/watch?v=IyBsTa6Z1w4