Clear tail lights are quite popular today and appear on several new models as standard or optional equipment from the Toyota Prius to the Porsche 911 and Aston Martin Vantage. Many people mistakenly believe they were introduced in 1998 with the debut of the Toyota Altezza (Lexus IS) although the Toyota actually only had conventional tail lamps covered by clear acrylic; the design did not conceal the underlying red filter lenses. Clear tail lamps, like so many automotive technologies, actually first surfaced in the 1960s. Many of them were more sophisticated than some recent examples.
Their first application was the Three-Phase Rear Lighting System developed by the Guide Division of General Motors for the 1962 Cadillac. These innovative rear light clusters not only incorporated clear lenses, they were also bi-colour, a novel execution that has been revisited only recently by using dual-colour LED technology.
The transparent lenses on the bumper-mounted lamps emitted both white and red light, thus serving as tail, brake and reversing lamps; all transmitting light energy through a single clear lens. The secret was a concealed red glass filter enclosing the dual-filament tail and brake lamp bulb combined with a second unsheathed bulb producing white light for reversing, both contained within a common reflector housing.
Variations of this innovative bi-colour design would continue to be utilized by Cadillac for all but the final year of the decade.
For ’63, the lamp assemblies consisted of upper and lower sections separated by a small rectangular red reflector. The tail and brake lamps transmitted red light out through both the red upper and clear lower lenses.
In this updated version, a centrally-mounted forward-facing dual-filament bulb directed light both upwards and downwards through a pair of flat horizontal Fresnel lenses directing light to the focal points of twin parabolic reflectors. Below the lower Fresnel was a red acrylic filter allowing only red light into the clear lower section for brake and tail lamp functions. A single-filament bulb located below the red filter projected white light directly out through the lower lens when reversing.
The 1964 iteration was the most dramatically executed example of the Cadillac bi-colour design. The centre forward-facing dual-filament bulb was retained, but this time a U-shaped red filter intercepted light travelling both upwards and downwards to enable the use of a clear lens from top to bottom, bisected by a small chrome-embellished reflector assembly.
In ‘65 and ‘66, Cadillac stylists added a small visible area of translucent red to the outer lens surrounded by the traditional clear, necessitating a new four-sided pyramid-shaped internal colour filter.
Not to be outshone, Chrysler incorporated clear tail lamps into the design of the all-new 1965 New Yorker, differentiating it from its lower-priced siblings that had to make do with conventional red-lensed lamps.
In what was the decade’s most striking application of clear tail light lenses, the lamps on the New Yorker were visually united by a textured aluminium centre panel, resulting in a broad silver accent extending the width of the car. Because the lenses were not recessed like the Cadillac units or as heavily textured, the clear nature of the lenses was more readily apparent to the casual observer.
Unlike the Cadillac designs, these were not bi-colour. The inboard segments were conventional reversing lamps, while the outboard sections were tail and stop lamps that emitted red-filtered light only. The small red inset rectangles provided the necessary reflective capability.
Ford weighed in with their own approach for the 1966 Thunderbird using a clear centre insert with bi-colour capability that incorporated reversing lamp functionality into a full-width single tail lamp assembly. This transparent centre section incorporated three red-filtered dual-filament bulbs interspersed by a pair of unfiltered bulbs for reversing.
At night, an array of no less than nine light bulbs distributed red light across the entire width of the Thunderbird, piercing the veil of darkness with over seventy watts of scarlet illumination through both red and clear portions of the lamp cluster. When required, the twin reversing lamps would send white light out through the clear centre portion.
The Thunderbird lost the bi-colour feature for 1967, though it was briefly reintroduced on a much smaller scale for the ’70 and ’71 models.
By then the clear tail lamp trend had run its course and would inexplicably lie dormant for years. After nearly two decades Cadillac briefly reintroduced them on Allantés and Fleetwood Broughams, but the style would ultimately be revived not by the American firms that spawned it, but by Japanese and European manufacturers at the turn of the century.
Clear tail lamps have now come full circle as General Motors, the originator of clear taillight technology, recently reintroduced them on the 2015 Corvette Z06, fifty-three years after they first graced the stern of a Cadillac.