That’s right, friends, I realize it’s summer, but it’s time again for us to enroll in Taillight University, because taillight appreciation and knowledge doesn’t take vacations. Today I want to address the strange but recurring fetish in Taillghtdom for the White or Clear Taillight, and to specifically focus on the pioneer of this trend, Cadillac’s Three-Phase Rear Lighting System.

Before we get to the Caddy, though, let me just remind you of this unusual yet persistent styling trend in taillight design.

Even though the accepted base color for taillights, the color that literally defines the rear of a car, is red, at various times over the course of automotive styling history, designers have been tempted to hide the rearward redness of taillights by making them—in their un-illuminated states, at least—appear white or clear.

Personally, I always find this a little jarring-looking, even though sometimes I do appreciate the novelty. The “Altezza” taillight trend of the late 1990s and early 2000s is perhaps the best-known version of this design concept, though there are certainly bolder non-red examples to be found.

Here’s a sampling, in case you forgot what these non-red taillights are like:

You’ll note that this concept has been used by a number of different carmakers from all over the world, with varying degrees of success. Each of these versions is similar in that they all must include at least some amount of red reflector (the Saab one is a real purist, sticking the reflectors on the bumper below) and they all still have red stop and taillights, amber or red turn indicators, and clear reverse lamps when illuminated.

Most of these setups just have different compartments for the various light functions. The original clear-taillight pioneers at Cadillac, though, took things a step further with their Three-Phase Rear Lighting system, having one primary chamber that changed colors based on use, even in an era long before bi-color LEDs would make this easy.

The best—and pretty much only—source on the web that talks about this in any detail is this , and he does an excellent job describing why Cadillac’s system was so good.

The 1962 Cadillac de Ville design was still firmly in the tailfin era, but by 1962 Cadillac had freed itself from the bulbous, pneumatic shapes of the 1950s and had developed their own refined, handsome, and very crisp design vocabulary, full of smart creases and elegant, if imposing, proportions.

The Cadillac of 1962 was the undisputed car to aspire to, and as such had to convey status everywhere it could, and that included government-required bits like taillights.

Cadillac spent considerable effort designing a rear lighting system that stood out from the crowd and reminded all those plebs in their Dodges and Ramblers just what they were looking at as they were forced to stare at the taillights of the glorious Caddy chariot in front of them.

Cadillac was so proud that they even gave their taillight innovation a name, the Three-Phase Rear Lighting System I mentioned earlier. Essentially, it worked like this:

Or, maybe it would be better to actually show you, with this 1962 Cadillac Dealer training video that highlights the Three-Phase System at 3:33 in:

(Right before the taillight part starts,

Even though the video quality isn’t great, you can see what’s going on reasonably well:

This appears to be default taillight mode; in reality, the light would be much redder than this old video shows.

Brake lights illuminate all elements bright red, of course. But here’s where it gets interesting:

When you reverse, the whole lower pod glows bright white, providing a nice strong reverse lamp, while the upper tailfin light wedge remains red, providing brake/tail/and turn functionality.

What’s cool here is that lower pod seamlessly changes color from red to white light, in a way that must have seemed pretty cutting-edge to drivers back in 1962.

It wasn’t terribly complicated, really—there was one dual-filament bulb inside with a well-concealed red lens, and one single-filament bulb that was just bare, but the result was striking and novel. Cadillac liked the concept so much they kept using it in Sedan and Coupe de Ville taillights, in various designs and configurations, up until 1968.

With LEDs that can immediately change color from red to amber to clear with minimal complexity, I feel like we may be seeing more and more new takes on the old clear, unsegmented taillight concept.

While I still have some fundamental issues with the concept (I think it helps to know where to expect a given signal light to be) I can’t deny that these can make for some striking rear-end designs, so I hope we’ll see more bold taillight experiments to come.