How Car Lights and Signals Work and What do they Mean?

Car signals are one of those pieces of car mechanics that we don’t often give much thought to. We learn how to use them to get through the driver test. Sometimes we get annoyed with other drivers who don’t use them. We may wonder whether we’re using them right in other states. Most of us certainly don’t know much about the mechanics of them.

But here at Parkhound, we think about car signals a lot! We have members of the Parkhound community everywhere from Sydney to Perth. So we know that there’s some confusion about signalling rules in different states. Have you ever had a car light go out? You might wish you knew more about how these lights work. You’d then be able to fix them yourself.

No matter what your question about car signals, this guide has the answer. By the end, you’re going to be a car signals expert!

Question #1: Are car signals universal?

As you could probably guess, the general concept of car signalling is the same wherever you are in Australia. Use your left indicator to signify to other drivers that you’re turning left or entering the lane on your left. The right indicator light shows that you’re turning right or entering the lane on your right. It’s also standard that you need to signal whenever you pull onto or off of a thoroughfare. Signal also while making a U-turn or 3-point turn, leave a roundabout, or enter or leave a car park. 

From state to state, you can also assume that the rules about the timing of your signals will be similar. The Driver’s Handbook for South Australia states that if you’re parked on the side of a road and wish to drive into traffic, you must signal for at least 5 seconds to warn drivers and cyclists. NSW, QLD, and VIC all have the same 5 second rule about driving away from a stationary or parked position. 

There is a bit of nuance about timing. Most states state that you should signal for enough time so that other drivers and cyclists can see your signal. VIC requires that drivers signal for a specific three seconds or more.

The rules for light signals are pretty much universal across Australia. So why is it that so many people make the mistake of not using them regularly? Unfortunately, this driving rule can be difficult to enforce. Many don’t see the importance of using their turn signals until they’ve had an accident. No matter where you are in Australia, get into the habit of using your car lights all the time. That way you don’t forget when it really counts. 

Question #2: Are car signals the same in every country?

Again, you won’t find much difference in terms of car signal regulations country to country. Although some places will more strictly enforce their driving laws. In some cities around the world, you might wonder whether drivers even know how to locate their car signals. In others, you can find drivers using their car lights diligently. But in general, all drivers rely on the basic principles: signal left to merge left or turn left, signal right for the opposite, and using your hazard lights for emergencies.

Yet, there is one global divide about car lights that might surprise you: indicator colour. Here in Australia, we’re accustomed to yellow or amber turn signal lights. But that’s not the case everywhere. In North America, rear car signals can be either red or amber. A 1995 study on reaction times even found that drivers reacted quicker to cars with amber turn lights.

Question #3: When did car signals become a thing?

It’s easy to assume that car signals have been around as long as cars. The truth is though, most drivers relied on hand signals for decades after the invention of the first automobile.

No one was completely happy with having to use their arm as an indicator, especially in the rain and snow. In fact, as early as 1909, British inventor, Percy Douglas-Hamilton applied for a patent for his device. It would indicate the direction of a moving vehicle. His idea started the conversation around automatic signalling but didn’t quite catch. If it had, we might all be driving around with hand-shaped lights on our fenders. They’d be pointing in the direction we want to go in!

By the 1930s, car signals had developed into something more easily replicated on a mass-scale: an indicator light with arrows. And in 1939, Buick made the leap to standardise these early car lights. He also added something else very important: the ability to have the light blink or flash. 

Surprisingly, flashing car signals weren’t a worldwide phenomenon until well into the 1950s. Nowadays, we can’t imagine life without them.

Question #4: How, really, do car lights work?

Alright you electrical engineering enthusiasts, it’s time to talk about indicator light circuitry! How do these little flashing lights function? 

It might surprise you to know that indicator car lights are quite complex. While you can fix them by simply replacing the bulb, the entire mechanism is made up of many different parts. And what your turn signal system looks like depends on when your car was made.

Let’s start with the traditional way that flashing car signals work. 

In older cars, when you engage the turn signal, you’re prompting your car to send power from the car battery to the turn signal flasher, sometimes called the thermal flasher or turn signal relay. You can generally find this small cylindrical device on the fuse panel under the car dashboard. The thermal flasher then connects to the actual indicator lights at the front and back of your car.

To understand what’s happening in terms of the electrical mechanism, we should take a closer look at that thermal flasher. This is responsible for sending power to the indicator light. But remember, the flasher can’t send a steady current to the indicator light. We would just get an unblinking light otherwise. In order to add the flashing ability, the thermal flasher relies on a flexible bi-metallic strip and a heating coil. When current runs through the flasher, it first heats up the heating coil. This then heats up the bi-metallic strip, causing it to flatten. When the bi-metallic strip is flattened, current can flow freely to the indicator light. This free flow of current to the indicator light means that the heating coil cools down. This in turn cools down the bi-metallic strip, thus interrupting the current to the light. The process starts over again, repeating one or two times per second, and giving us a lovely flashing turn signal.

If there’s an issue with your indicator lights, it could mean a problem with this circuitry. If replacing the bulb doesn’t fix the problem, it could mean the thermal flasher has to be replaced. But no worries. It’s an easy and cheap fix.

Now, how about modern cars? Well, instead of relying on springs and heating coils, modern cars engage the indicator light through computer commands. In fact, that mechanical click that you hear when you engage a modern car indicator is entirely fabricated for effect. After all, it would be quite strange not to hear the clicking of your car signals.

Any other questions about car signals? Send them our way!

Here at Parkhound, we love to hear your car related questions. Whether you’re looking for cheap parking spaces to rent in Brisbane or Canberra, or you’re wondering about the early prototypes for car signals, we’ve got the answers you’re looking for!