It pioneered the design of rear-engined, front entrance double deck buses in the UK, allowing for the introduction of "one person operated" buses, dispensing with the need for a conductor.
In the years immediately following the Second World War, bus operators in the UK faced a downturn in the numbers of passengers carried and manufacturers began looking at ways to economise. A few experimental rear-engined buses had been produced before the war but none successfully made it beyond the prototype stage. The need to minimise the intrusion of the engine into passenger carrying space was a priority, leading to several underfloor-engined single-deck designs. However, such designs raised the height of the floor of the vehicle, forcing additional steps at the entrance. On double decker buses, these problems were amplified, causing either an increase in the overall height of the vehicle or an inadequate interior height.
In 1952, Leyland began experimenting with ideas for a rear-engined double-decker bus. A prototype was built, with a body by SARO, to the maximum permitted width of 7 feet 6 inches (2.29 m). It was fitted with a turbocharged version of the Leyland O.350 engine, which was transversely mounted at the rear of the sub-frame. The chassis was a platform-type frame of steel and light alloy with deep stressed side-members. An automatic clutch and self change gearbox were also fitted. The vehicle, numbered 530001, registered STF90 was designated the PDR1 (R for "Rear-engined").
In 1956, a second prototype, XTC684 (No. 542209) was constructed, this time with a Metro-Cammell body and, again equipped with the O.350 engine fitted across the frame. It had a centrifugal clutch, pneumatic cyclic gearbox and angle drive. This vehicle was 13 feet 2.75 inches (4.0323 m) in height, with a 16-foot-2.875-inch (4.94983 m) wheelbase and overall length of 29 feet 10 inches (9.09 m) and had a seating capacity of 78. Leyland christened this prototype the Lowloader.
Though two prototypes were thoroughly tested, the same problem of a front-engined bus remained — they had rear entrances with the space alongside the driver being wasted.
An amendment to the Construction and Use Regulations in 1956 saw the maximum length for double-deckers increased to 30 feet (9.1 m), allowing a wider entrance to be located ahead of the front axle. This was initially to allow the driver to supervise boarding whilst the conductor collected fares, but quickly it became apparent that the design would allow for one-person-operation. Leyland took advantage of the new regulation to launch the first prototype Atlantean at the 1956 Commercial Motor Show at Earls Court. Though it featured the front entrance design that would redefine the bus industry, several factors prevented the bus going on the market. The main problem was the high level of engine noise inside the lower saloon, as the engine was still inside the body, with the compartment being used for bench seating.
Mechanically, the prototype Atlantean, 281 ATC, was similar to the Lowloader — an O.600 engine transversely mounted at the rear with a pneumo-cyclic gearbox situated in the rear offside corner providing drive in a straight line from the engine. The Atlantean had a light and strong fabricated frame. Light alloy floor plates were rivetted directly to the framework, fulfilling the dual purpose of reinforcing the frame and providing a foundation for the saloon floor. The platform-type sub-frame concept from the Lowloader was retained for the prototype. A drop-centre rear axle allowed the flat floor, only one step up from ground level, to continue for the full length of the bus.
The prototype was demonstrated around the country to various operators. It also had an unregistered sister vehicle, which was used as a testbed. Both were subsequently scrapped.
By 1958, Leyland had overcome most of the problems and moved the engine to a rear-mounted compartment outside the main body and the first production Atlantean PDR1/1, with a 16-foot-3-inch (4.95 m) wheelbase, was launched at the 1958 Commercial Motor Show. It had simpler mechanical specification than the prototype, with conventional front and rear axles, leaf springs all round and a channel section frame. Glasgow Corporation, James of Ammanford and Wallasey Corporation each put their first example of the type into service in December 1958.
From 1964, a drop-centre rear axle was available as an option for the Atlantean; the Atlanteans with drop-centre rear axles became known as the Atlantean PDR1/2 and, for the later version, the Atlantean PDR1/3. In 1967, Leyland launched the Atlantean PDR2/1 which could be fitted with 33-foot-long bodywork (10 m).
Though some operators initially continued to buy front-engined vehicles for reliability, the Atlantean became very popular. Though the National Bus Company and the Scottish Bus Group favoured the Bristol VR and Daimler Fleetline respectively, the Atlantean proved popular with municipal operators. Aberdeen, Bournemouth, Glasgow, Edinburgh, Newcastle, Manchester, Liverpool, Newport, Nottingham and Plymouth Corporations purchased large numbers of the type. A number of Atlanteans were exported, including 224 for PTC/UTA (now State Transit Authority) in Sydney, Australia.
By 1972, over 6,000 Atlanteans had entered service.
In February 1972, Leyland announced the AN68 series to replace the PDR1/PDR2. The new chassis provided a wider entrance and several new safety features were included. An audible and visible alarm discouraged engine overheating by giving the driver due warning. A fail-safe parking brake was introduced, while the steering box and brake controls were protected against damage from severe head-on collision and stainless steel air-piping gave greater resistance to corrosion.
Two models were offered: AN68/1R (9.4m in length) and AN68/2R (10.2m in length). Power assisted steering was standard on the AN68/2R and optional on the AN68/1R. The steering pump was power driven, which replaced the early belt driven system, while the only available engine was the new Leyland O.680. A wide variety of body styles from various manufacturers continued to be offered, allowing the Atlantean to be tailor made to requirements from operators ranging from the small independent to the large city corporation.
In 1978, Leyland started to offer the AN69 with Leyland O.690 (a turbocharged variant of the O.680) engine which was mainly built for export.
The Atlantean continued to sell in large numbers, with many operators proving loyal to it. London Transport (LT), however, notably chose the Daimler (later Leyland) Fleetline over the AN68 for its first large rear-engined double-deck order. Though over 2,000 Fleetlines would be purchased by LT, reliability problems and LT's rigid maintenance system caused their very premature withdrawal.
The creation of British Leyland in 1968 saw rivals Daimler and Bristol merged with Leyland, bringing the two competing rear-engined chassis (Daimler Fleetline and Bristol VR) together with the Atlantean. Though the Bristol brand was retained, Daimler was dropped and products were re-badged as Leylands. After the re-organisation, Leyland set out to develop a new rear-engined double-deck bus for the London market to replace the troublesome Fleetlines. This new vehicle, the Titan B15 spawned a simpler, non-integral offshoot, the Olympian, which debuted in 1980. Though the Olympian was meant as a direct replacement for the VR, Fleetline and Atlantean, the venerable AN68 continued in production alongside the Olympian until 1986. The last Atlantean for the domestic market rolled off the production line in 1984, the last of a batch for Merseyside PTE, while the export version remained in production for a further two years, with deliveries to the city operator in Baghdad, the capital city of Iraq.
By the end of production, over 15,000 Atlanteans had been built. Greater Manchester PTE (and its predecessors) was the largest operator of the Atlantean with 'Greater Manchester Standard' bodies from Northern Counties and, to a lesser extent, Park Royal. Second was Glasgow Corporation/Greater Glasgow PTE most of which were bodied by Walter Alexander. Third was Merseyside PTE who took approximately 800 Atlanteans mostly bodied by Walter Alexander and East Lancs although there were smaller batches with MCW and Willowbrook bodies. Notably, the fourth largest was Singapore Bus Service from Singapore; it had received 520 Leyland Atlantean AN68/2Rs in 1977–86 in three batches with the bodywork provided by Metal Sections/Duple Metsec, British Aluminium Company and Walter Alexander. The Singapore-based Leyland Atlanteans were withdrawn between 1993 and 2001.
Though the Atlantean was the first high-volume rear-engined double-decker on the market, Daimler was quick to catch up with its Fleetline model. Bristol followed several years later with its VRT.
The Bristol was favoured by the state-owned National Bus Company, several of whose predecessors had standardised on Bristol vehicles. Several early examples were also purchased by NBC's Scottish sister company, the Scottish Bus Group, where the front-engined Bristol Lodekka had proved popular. However, the Scottish customers did not share the same enthusiasm for the VR and the vehicles purchased were swapped for ex-NBC Lodekkas. The Scottish Bus Group then standardised on the Daimler Fleetline for its double-deck needs.
After the re-organisation of British Leyland, both VR and Fleetline became Leyland offerings and, when production of both ceased in 1981, over 6,400 VRs and 11,500 Fleetlines had been built. Frustrated at the lack of competition to Leyland, some operators turned to other manufacturers, who began to offer alternatives to the state-owned manufacturer. Supply problems at Leyland did not help matters and products such as the Scania Metropolitan and Dennis Dominator began to make small inroads into the rear-engined market, while the Volvo-backed Ailsa reintroduced a front-engined double-deck chassis, with a front entrance, with some success. The Scania/Metro Cammell Weymann partnership, which produced the Metropolitan, ended in the late 1970s and forced MCW to introduce its own rear-engined product, available as an integral or chassis, the Metrobus. The success of the Metrobus, particularly with West Midlands PTE and London Transport, would spur Leyland on to develop a new heavy-duty rear-engined bus, sealing the eventual withdrawal of the Atlantean from the market.