Media

ca. 1967 GMC RTX Prototype

The public may have ogled Chevrolet's swoopy Astro II or Aerovette concept cars make the 1968 auto show circuit, but another GM concept - arguably just as futuristic - was virtually invisible, even in spite of its size: the GMC Rapid Transit Experimental (RTX) bus.

At the time, GM's New Look (aka "Fishbowl") bus was a dominant force in the North American transit industry, but that didn't mean there weren't areas that could be improved upon. It did have a few faults - perhaps most notably that it wasn't accessible or accommodating to passengers with limited mobility.

From a business standpoint, Truck & Coach also needed to make the coach "sexy" – this was the swinging 'Sixties, after all, and the American public’s love affair with the automobile made selling mass transit to the average consumer difficult. In order to lure a typical commuter away from the privately-owned car, a new bus had to be quick, comfortable and above all, attractive.

The RTX was certainly that. If the coach looks modern today, consider how outlandish it was during its debut four decades ago. Previous transit buses were ungainly, sporting fluted aluminum sides with exposed rivets. In contrast, the smooth, flush surfaces of the RTX's body were more akin to a spaceship than a bus. Windows - nearly three times the size of those on older coaches - were flush with the body, which also sported fiberglass panels hung on its underlying structure.

(left to right)
ca. 1974 GMC RTS-2 Experimental Coach
ca. 1974 GMC RTX Experimental Coach

That structure was just as innovative as the RTX's appearance. While older coaches had unique stampings for 30-, 35- and 40-foot models, GM developed a system - consisting of five-foot long modules - that allowed for a variety of lengths to be manufactured with minimal tooling change. Perhaps more important - at least to passengers - was the use of a low-floor design. While 'normal' buses had a floor nearly 32 inches above the road surface (and tall steps to reach it), the RTX's floor height measured in at only 21 inches. By deflating the front suspension's air bags in a "kneeling" function, that could be cut to as low as 15 inches. This ultra-low height was attained with the use of 16.5-inch tires from Firestone, although their limited weight capacity mandated the use of a second rear axle.
Passengers certainly noticed a large departure from a typical bus inside. Inspired by the advent of first-class aircraft, designers decided to give the RTX: bucket seating, shag carpeting and multiple climate control zones. Adding to a commuter's pleasure was that the RTX was designed to move quickly. GM's Research Laboratories donated a 280-horsepower GT-309 gas turbine and a toric-type continuously-variable transmission, allowing the 40-foot long bus to cruise at speeds around 70 mph.

Those lucky enough to ride within the RTX were limited to those attending industry shows (like the 1968 APTA (American Public Transportation Association) conference in Cleveland or TRANSPO 72 (1972 U.S. International Transportation Exposition) show in Washington D.C., who also fell in love with other gizmos like HID (high-intensity discharge) headlamps and oil-cooled disc brakes. Certainly, the RTX was a "pie-in the sky" idea that never quite came of age, but its basic design helped launch the Rapid Transit Series (RTS) bus, which - from 1977 until 2007 - was a more than familiar face on the streets of America.

-Evan McCausland

Video Courtesy of General Motors Archive - ca. 1970

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