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Trendsetter in local public transport: In 1973 the O 307 entered series production
- Tailor-made for the customer's needs
- Modular system for city and inter-urban regular service buses
- Best-selling inter-urban bus of the 1970s
Wide doors, high windows, clear passenger information, plenty of interior space and comfortable seats; an ergonomically designed cockpit for one-man operation and quiet, clean engines. Nowadays these are the features that characterize the familiar appearance of modern regular service buses. When the O 307 inter-urban bus entered series production in February 1973, attributes such as these were anything but the norm. The drive for modernization which commenced in the mid-1960s was primarily due to the initiative of the transport operators. In addition to being strongly dependent on the satisfaction of their own customers, the passengers, the operators also hoped that the standardization of regular service buses would produce financial savings, not least because of reduced costs for servicing, maintenance and replacement parts inventories.
The birth of the standard inter-urban bus
It was Hamburger Hochbahn AG that started the ball rolling on the instigation of its Technical Director O. W. O. Schulz. At the 1967 annual meeting of the Association of German Transport Operators (VÖV), this company was able to persuade the member organizations to issue recommended model specifications which would standardize city service buses. The fact that the members of the working group which produced this recommendation operated more than 70 percent of all city service buses in Germany gave the necessary weight to their demands. That same year Daimler-Benz, Magirus and Büssing presented prototypes of the standard city bus at the International Commercial Vehicle Show (IAA). They were received with some suspicion.
At that time the German market was serviced by six bus manufacturers whose models with their chrome trim and comfortable, rounded contours were still very reminiscent of the 1950s. Indeed the rationalized, rectangular city bus, which had very little in common with its homely predecessors, was initially sneered at as a "people container". The manufacturers too did not always find it easy to adjust to the new concept, even though they made haste to meet the wishes of their customers. Until then they had all followed their own ideas with respect to dimensions, engines and appointments, and these were not always easy to reconcile with the new requirements.
The market leader Daimler-Benz had just presented the new O 302 model series in 1965. In view of the relatively low volumes for individual segments such as inter-urban services, the Mannheim plant planned to cater for the entire spectrum of operations, from the city bus to the comfortable touring coach, with a single model series. However this model was far from meeting the requirements which the Association announced two years later.
Moreover, at the turn of the year 1967/68 a further working group consisting of representatives of the German railway and postal services, as well as associations of passenger transport operators and private sector railways was formed. This working group undertook the task of developing its own guidelines for a standard inter-urban service bus along the lines of the standard city service bus. It presented its recommendations in 1969. The following year Daimler-Benz presented a prototype at the "Rail and Road" exhibition in Essen, and series production of the O 307 standard inter-urban service bus commenced in February 1973.
Demanding specifications for the standard inter-urban service bus
Whereas the O 302 had been designed to cater for both city and inter-urban operations, there was to be a major difference between the standard inter-urban bus and the city bus, for in 1967 the VÖV had specified a low floor height for city buses to make it as easy as possible for passengers to enter and leave the vehicle. The inter-urban bus, however, was to have a luggage compartment with a capacity of at least 2.5 cubic meters which could only be accommodated beneath the floor, between the axles.
Moreover, with a length of 11.7 meters the inter-urban bus was to be slightly longer than the 11-meter VÖV city bus. Comfortable seat rows were to be provided for roughly half of the 102 passengers. Where the cockpit was concerned the working group followed the lead of the city bus. The engine output was to be in the region of 200 hp.
Daimler-Benz responds with the O 307
It was therefore clear that city and inter-urban operations could not be combined in a single model series. Nonetheless Daimler-Benz did not miss the opportunity to include its own rationalization efforts in the design concept for the inter-urban bus, and made sure that the greatest possible number of O 305 city bus components were adopted in the O 307, which was presented in 1973. These included not only frame and body components, but also the highly praised, practical and clearly arranged cockpit.
Conversely the city bus adopted the 210 hp six-cylinder OM 407h engine from the O 307 in 1973, replacing the original OM 360h which had an output of only 192 hp. This eleven-liter engine was installed horizontally at the rear, with a 180 hp low-emission variant also available on request. In 1973 Daimler-Benz also introduced a sound-insulated version, the "whispering bus". To quote a press release: "The engine encapsulation system reduces engine noise to such an extent that the engine of a passing bus can scarcely be heard."
Passenger comfort and safety
The O 307 was able to seat 53 passengers in 14 seat rows, with standing room for 48 more. At 879 millimeters the floor level was 150 millimeters higher than in the O 305. The double rear door was 1200 millimeters wide as in the city bus, however at the front the O 307 made do with an entry width of 730 millimeters. With a capacity of approx. three cubic meters the luggage compartment even exceeded the requirement of the working group.
Comfort was ensured by air suspension as standard, as in the O 305, while large side windows provided good visibility. At the front end the two ventilation louvers on both sides of the destination indicator were immediately noticeable. In conjunction with the roof vents, two slim quarterlights in the last pair of windows and a generous heating system, these provided a pleasant interior atmosphere at any time of the year.
Passenger safety was ensured by a Westinghouse self-adjusting, dual-circuit braking system acting on all four wheels. Measurements with a fully-laden bus weighing a total of 15.6 tons showed a braking distance of 30 meters in emergency braking from a speed of 50 km/h.
The cockpit was practically identical to that of the O 305: a hydraulically damped driver's seat with longitudinal and height adjustment ensured comfortable access to the clearly arranged instruments and controls. Power steering assisted by a steering damper, as well as a turning circle of only 22.3 meters, made slow-speed maneuvers easier in bus stop bays and narrow areas.
Power was transferred to the rear planetary axle by either a synchronized five-speed manual transmission or a three-speed automatic transmission. In both cases the gear gradations and the performance characteristics of the engine provided both excellent acceleration and a low level of vibrations at low engine speeds. In fourth gear the speed could be reduced to almost 20 km/h without any significant vibrations occurring.
One thing had changed versus the O 305, however: the prototype of the city bus had already attracted criticism with its unusual, very deep windshield which curved outward like a sail. Accordingly Daimler-Benz modified the windshield and improved the aerodynamics at the same time. In the O 307 the windshield was also rounded off at the edges, significantly reducing the air resistance to a Cd figure of 0.42.
Emphasis on ease of servicing and maintenance
The requirements of the transport operators for a vehicle with a long operating life and easy maintenance were not only met by the well-proven quality of the engine, the robust suspension and strong body components. The engine compartment and fuel tank, batteries, auxiliary heater and electrical system were also easily accessible via large external maintenance flaps.
And in case something should go wrong despite careful maintenance, twelve specialized workshops and 885 customer service outlets throughout Germany were available to give the operator advice and assistance. In the event of a breakdown a company-operated emergency service was on the spot in next to no time.
Best-selling bus in its class – award winner for excellence
In one respect this standardization of city and inter-urban buses did not quite meet the expectations of the transport operators, for although the ongoing costs for servicing and maintenance were significantly reduced, the purchase price increased. Whereas Daimler-Benz had offered the O 302 for DM 65,000 to 88,000 in 1966, the O 307 started at no less than DM 140,000, even rising to DM 290,000 by 1984.
Quality simply has its price, and this was recognized by Daimler-Benz customers. Up to 1984 they ordered 3,985 units of the O 307, making it one of the best-selling inter-urban buses of the 1970s. In doing so the customers confirmed the verdict already reached by the specialist world: at the 1973 International Bus Week in Nice the O 307 was immediately awarded the "Grand Prix Louis Bolandard" for technical excellence.