This photo is part of an extensive collection of airport signage and navaids that i'll be sharing with you. The double solid double broken lines you see are runway hold short bars. Pilots taxiing know that when they approach these lines, they are about to enter a runway. If it is an active runway (meaning currently in use), the pilot had better get ATC clearance to enter that runway or risk runway incursion which unfortunately does happen numerous times every year at many airports. Seen here is runway 25R on the south side of LAX and Delta Connection EMB145 on takeoff roll
