Advance Warning Lights Are Good

As drivers, we have a hard decision to make when a traffic signal turns from green to yellow. Technically that means come to a stop ASAP, but there are dozens of things that happen when we see that yellow. We have to judge not only whether we can stop in a short enough distance to not be a safety hazard, but whether the car behind us is too close to our back bumper to safely navigate the same stop. Are they paying attention? Are there any cops around?


The Association for Psychological Science calls this split second decision one of the more dangerous encounters on the road. Traffic signal intersection crashes happen literally every day, resulting in millions of bent up cars and hundreds of thousands of injuries, and a significant percentage of which are fatal.

Inspired by yesterday’s discussion of pedestrian safety, I was thinking about what my local municipalities do well, and how we could improve. One way that is proven to work is the use of advance warning lights.

Here in Nevada—and some other states—we have advance warning lights that warn you a yellow is coming at the traffic light up ahead. By knowing the light will be yellow or red by the time you reach it, you can back off the throttle further up stream, which helps save a little bit of fuel and wear and tear on your car’s braking system. You have a lot more time to slowly get on the brakes to ensure the person behind you isn’t startled by your brake application, or has time to look up from their text thread.

Some states use a system like the one shown in the picture above, which only flashes when the signal is red. That’s helpful, but the one in my home state is even more effective.

I do a lot of driving and I’ve seen a number of different systems used in different states, but the one in California is by far the most asinine. Just across the border from Nevada, California uses a visually very similar system. The yellow diamond sign depicts a typical three-light traffic signal with two yellow flashing lights attached to the pole. In Nevada those lights only flash when the signal is about to turn yellow, is yellow, or is red. In California they flash all the time. It’s a warning light to warn you that there is a signal up ahead. It might be green, but you won’t know until you get there. It does nothing.

Anyway, the system we use locally is very good, and I like it. It is particularly effective when you are stopping from higher speeds, as we have a number of roads with 55 or 60 MPH speed limits with these stop lights facilitating entry to or exit from shopping centers and neighborhoods. I’m not saying our system works for every scenario, but many rural areas of the country could benefit from something like this. But more importantly, I think we can all agree that California’s system is useless.


Be safe out there.

Jalopnik contributor with a love for everything sketchy and eclectic.


Theres a few of these on the Colorado front range for state highways and other major roads that have high speeds but occassional stop lights.

I’ve always thought they worked well because I always intuited that they knew when to start flashing if the traffic at the warning would arrive at the light when it became red, even if it was not yet yellow...

Then suddenly there was quite a bit of discussion about how annoying these are and how “we drive these roads all the time- we know where the lights are” (lots of long curves through forest and hills- lots of lights you’d never see in time) and “they’re broken and dont flash half the time! It’ll make people think theres no light and they wont look!” clearly the logical intuition that these lights warn you that you’ll be approaching a red even if it isnt red yet is lost on a huge number of people.

A friend of mine, an educated and talented engineer, was complaining about them- I explained the actual purpose and function and he cut me off... “no no thats not how they work- think about it, how could the sign know when the light is GOING to be red? Does it guess? What if it was wrong? That would be a ridiculous system- they’re just there to warn you that there IS a light, not what the light is doing.”

There’s just no accounting for the rarity of common sense.