This circuit uses the TLC555CP timer I.C. to flash an LED roughly twice every second. This particular type of 555 timer will run off only 3 volts so two 1.5 volt cells can be used. With "AA" cells, you can expect a battery life of up to 6 months. With larger "C" or "D" type cells it will last for years.
The circuit can be incorporated into a roadside lane marker bollard or used as a warning for other obstacles such as fences, scaffolding tubes or parked vehicles. It can also be suspended from light switch pull-cords to make them easy to find in the dark.