Vintage Ad/Bus Stop Classic: 1932 Ford V8 Tri-Coach – Driven From The Semi Trailer

Here’s something a bit different: a semi-trailer coach/bus that’s driven from the trailer. There were sound reasons for this, as it lowered overall height and weight, increased maneuverability, lowered the floor for easier entry and a lower center of gravity, and a few others, according to its designer and patent holder, George W. Yost. Built be Heisers, Inc., and called the Tri-Coach, a number were made and used in the Seattle area.

Here’s the patent drawings that show how it worked:


It appears that the steering column and gear shift went right through the center of the fifth wheel, which of course is the obvious solution.

As usual, that splendid repository of history,, has a long and detailed write up on Tri_coach. here’s the section relevant to this semi-trailer coach:

Constructed by Heisers, Inc., the original ‘Tri-Coach’ utilized a 98″ short-wheelbase 1 1-2-ton 4-cylinder Ford cowl and chassis, with the ‘fifth wheel’ suspension mounted about 18 inches forward of the power axle. The driver’s seat was inside of the passenger coach. The Tri-coach prototype was featured in a 1932 Standard Oil Bulletin:

“A Bus Conceived in Seattle

“Now in the service of the Suburban Transportation System, which operates busses between Edmonds, Richmond Beach, Lake Forest Park, Des Moines, Lake Burien, and Seattle, is a new type of motor-coach developed by that company, whose manager, George W. Yost, conceived it. As the accompanying illustrations show, it is of the truck-and-trailer type. Because of its comparatively light weight (7700 pounds), a four-cylinder Ford motor serves to give it ample speed and power.

“The truck is a standard Ford truck having a shortened wheel-base, its rear axle equipped with double wheels. Upon it is mounted a fifth-wheel, which supports the forward end of the passenger body, or trailer, in turn support toward the rear by a wide trailer axle that is equipped with brakes and dual rear wheels.

“Of the numerous advantages claimed for this motor-vehicle, our correspondent notes the following: its design permits a reduction in height; the elimination of all machinery from under the passenger section makes it possible to have a bus but one step off the ground, the low center of gravity thereby- achieved resulting in easier riding and reduced side-sway, as compared with busses having greater clearance. Also, it is asserted, there is an elimination of body twists, which is accomplished by the three-point suspension. This bus can complete a turn in a fifty-foot circle. The coach body, which is steam-heated, is of steel and aluminum, constructed by Heisers, Inc., of Seattle. Castings for the fifth wheel were manufactured by the Western Gear Works, also of Seattle, and the truck chassis was adapted to this special use by the Yost Auto Company, local Ford dealers. The weight and cost of this Seattle creation are asserted to be about half that of other busses of equal carrying capacity. It was planned and built with the idea of producing a bus that will render satisfactory service with a reduction of cost in operation. If, after an extended try-out in actual service, it meets the expectations of the designer and operators, others like it may replace those that constitute the present fleet of the Suburban Transportation System.

“It is operated exclusively on Standard Oil products, and its ten wheels, not including the fifth, appear to be a sweet potential market for Atlas tires.”

The Tri-coach was not the first trailer-bus of its type, back in 1929 aviator Glenn H. Curtiss had designed and constructed a series of nearly identical 5th wheel trailer buses that were put into service by the Transportation Co., Dallas, Texas and the Miami Beach Transportation Co. in Miami, Florida. In 1934 the Highland Body Co. of Cincinatti, Ohio offered their own take on the semi-trailer bus called the ‘Highland Acticulated Coach’ using equipment supplied by Trailmobile.

Yost’s Ford semi-trailer coach was also featured in the ‘What’s New In The Bus Market’ section of the February 1933 issue of Bus Transportation:

“Look! A Semi Trailer Coach

“Powered by a Standard four-cylinder Ford Truck which was shortened to a 98” wheelbase, a semi-trailer bus is being operated experimentally in service on the lines of the Suburban Transportation System, Seattle, Wash., George W. Yost, general manager of this organization is the inventor of this new type of coach and the body firm, Heisers, Inc., are the creators of this special all-metal body. The semi-trailer seats 26 passengers with full standing headroom for 20 more.”

In 1934 an improved Tri-Coach powered by a flathead Ford V-8 was put into operation. The bus was featured on a circa 1934-35 Ford postcard advertising it as a V-8 Semi-Trailer Coach. The back of the postcard stated it had seating for twenty-six with room for twenty standees:

“A wide choice of Body Types and Equipment adopt the Ford to ANY use… Ford V-8 costs 4 1/4 cents a mile… average fleet cost 9 1/4 cents a mile.”

Yost’s semi-trailer coach proved so successful that by the end of the year the Suburban Transportation System elected to replace its conventional motor coaches with Tri-Coaches, acquiring 3 more in 1935, 3 more in 1936, and 4 more in 1937.

It’s possible that Portland, Oregon’s Wentworth & Irwin may have constructed a few examples under license based on surviving pictures, one of which depicts a Tri-coach in service of the Vancouver-based British Columbia Electric Railway and another that shows a Suburban Transportation System unit with a Wentwin logo in the corner of the photo.

Due to pressure from larger motor coach manufacturers the Washington State Legislature passed a new traffic code in 1937 which made it illegal to carry passengers for hire in a trailer in the State.

Suburban Transportation System fought the new legislation, claiming its Tri-Coaches were not ‘trailer buses’, however they agreed not to build any more Tri-Coaches and the 12 coaches currently in service were ‘grandfathered in’ and remained in use into the early 1940s.

Yost went on to be very active with the firm Newell, which built trolley and buses of all sorts. also has pictures of two other variants of these Tri-Coaches.

A similar approach was used on a larger scale by the firm Dyson in Australia. Jim Brophy’s post on those remarkable coaches is here. Coincidentally, these were powered by two Ford flathead V8s.