LIPPO CIKARANG - Every once in a while you stumble upon a sign that can be very unclear without additional text. The picture below has been on my mobile phone for quite some time because I even forgot I made it some while ago. With the article about the nail-sweeping police (see related articles below) evidence of warnings come in handy.
Throwing nails on main roads occurs frequently on some main streets in Jakarta, like here on Jalan Gatot Subroto for example. You run a flat tire somewhere on this street and people will be there to change the tire for you if you are lucky. Less fortunate people get robbed in the middle of the night. In the worst case they will throw you out of the car as well.