Count Down Traffic Light

This was the first electronics product I designed at Arrow Emergency Systems. It is a traffic signal module that displays a countdown digit and a segmented circle within the amber aspect of a temporary traffic light.

When a road is reduced to a single lane using temporary signals, the wait times are often much longer than a normal intersection. If you’ve closed a few hundred meter stretch of road, if you arrive just as your light goes red, you have to wait for the vehicles that made the green too drive the road closure, wait for the 20-30 seconds of green at the other end, and then wait for those vehicles to traverse the road closure, with some extra time added for safety. For many an impatient driver, they see a temporary traffic light that is just red for five minutes and think it must have stopped working. The countdown timer on the amber was meant to give an indication to the driver that the traffic light is infact working.

The unit runs from the standard 12 V supply used in portable signals and illuminates like a regular amber lantern. While the signal is red it displays a countdown number and progressively extinguishes the segments of the circle. It is controlled over I²C and uses a switch-mode power supply generating 48 V to efficiently drive the background LEDs, with addressable LED drivers handling the digit and segment elements.

The product has now been in service for two years across multiple traffic sites in Victoria and Western Australia, and to date no lanterns have failed.