Q ver 20 years ago pundits were forecasting an end to
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the dominant position of the double-deck bus in British urban public transport. In many areas unions would not agree to one-man operation of deckers so high-capacity singledeckers such as the AEC Merlin came to the fore. Those crewing disputes were resolved, however. Despite a range of challenges from minibuses to bendibuses, the British public has continued its love affair with the double-decker bus.
The latest challenge to deckers comes from a crop of large single-deckers with ultra low floors. But in these uncertain times any large scale transfer of operations to large single-deckers is bound to be slow.
Britain's top selling double-deck bus chassis for a decade has been the Leyland Olympian: it is now the sole survivor of that once proud marque. If the Olympian is a reminder of past glories, so is its rivalry with the Dennis Dominator: over the years both have been refined into high-capacity PCVs with a worldwide reputation.
CM has borrowed an example of each from Hong Kong-owned Capital Citybus of Dagenham, Essex. Both buses entered service last April and both operate on tendered London Transport services. The Olympian is to the latest Leyland/ Volvo specification, powered by a Cummins L10 engine driving through a ZF 5HP500 automatic transmission. The Dennis is the first to be powered by the new Gardner LG1200 engine, also driving a ZF transmission. The Leyland — yes, it is still called a Leyland — is fitted with Leyland's own ECW body. The Dennis has Northern Counties "Countydec" coachwork. Both buses were taken straight out of service with no particular preparation and run over CM's decker test route.
• PRODUCT PROFILE
Our Olympian is the current standard twoaxle UK specification bus with an overall length of 9.6m and a wheelbase of 4.95m. Its body, which is now out of production, was built at the doomed Leyland Bus plant at Workington to a design developed for the National Bus Company before its privatisation. Although upgraded to meet DiPTAC and LRT schedule-X requirements, its interior is still reminiscent of the Leyland National single decker, It was launched in the early eighties with a choice of Leyland TLI I or Gardner 6LXB engines driving through Leyland Hydracyclic or Voith automatic transmissions. The only major change over the years has been the adoption of the Cummins L10/ZF driveline, although the 6LXB naturally aspirated Gardner is still available.
With an unladen weight of 9,615kg the Leyland-bodied bus is light by the standards of current double-deckers. It has a useful capacity of 93 passengers with 47 seats upstairs, 29 down and room for 17 standing.
Volvo offers the Olympian as an urban bus with the L 10, transversely mounted at the rear, rated to produce 134kW (180hp). The power is transmitted via the popular ZF gearbox and an angle drive to the Leyland drop-centre rear axle. The electronically controlled gearbox incorporates a retarder operated by initial pressure on the service brake. Air suspension is standard on all urban double-deckers: the Olympian uses a well-proven two-bag system at the front with four air bags mounted on a steel H-frame at the rear.
The cab remains pure eighties — vintage Leyland with its centrally mounted speedometer, rows of warning lights that are well placed (but difficult to see in bright sunlight). The rotary lights, starter and saloon and ancillary lighting switches are on a panel to the right of the driver, next to the push button gear selector and park brake lever. The black stove enamel finish of Leyland's seventies "ergonomic" styling now looks a little basic, but it's comfortable enough to work in.
The Dennis Dominator was launched in 1978 as one of the second-generation rearengined contenders to replace the ageing fleets of Leyland Atlanteans, Daimler Fleetlines and Bristol VTRs. It has never led the market, but sales have been steady and it has outlived competition such as the MCW Metrobus and Leyland Titan.
Our test vehicle is the first to be fitted with the latest turbocharged Gardner LG1200, driving through a ZF 4HP500 Ecomat automatic box. The standard Dominator driveline is a naturally aspirated Gardner 6LXB and three-speed Voith D851 automatic.
The Dominator has been described by one Capital Citybus executive as a "clever Fleetline". It has a traditional bolted and flitched chassis frame. Despite the Olympian's unusual perimeter-type construction the Dominator chassis is slightly heavier, at 6.7 tonnes against the Leyland/Volvo's 6.4.
Fitted with the all aluminium Northern Counties body the Dominator is over a tonne heavier than the Olympian, at 10.77 tonnes. Its glass-reinforced plastic seats are heavier than the Olympian's: the Dominator is licenced to carry 86 passengers (24 downstairs, 45 upstairs and 12 standing).
At 157kW (210hp) the 12.67-litre Gardner is more powerful than its 10-litre 134kW (180hp) Cummins rival. But the Gardner is shorter and more compact than either the L10 or its 6LXB stablemate. The LG1200 looks set to maintain the Gardner tradition of reliability and fuel efficiency in bus operation. Its specification includes traditional Gardner features such as its two detachable cast iron cylinder heads. It has a detachable one-piece cast iron cylinder block for simple top-end overhaul, dry cylinder liners and an integral oil cooler. IP.
The Dominator was launched with steel suspension but has followed the move to full air suspension. Like the Olympian it has two bags at the front and four at the rear.
The cab environment is less "corporate" than the Leyland-inspired Olympian design, but is equally practical with a central tachograph, twin air gauges, warning lights and all switches conveniently to hand.
The Northern Counties body is more lavishly furnished and finished than the Leyland. It features laminate panels, bright colours and moulded yellow seats. Like the Leyland it meets all current DiPTAC recommendations.
Both buses are well laid out from the maintenance point of view with their rear engines and ancillaries easily accessible for daily checks and routine attention.
• PRODUCTIVITY
With its lighter weight, slightly less powerful engine and slightly higher passenger carrying capacity the Olympian wins the productivity stakes. Predictably, its fuel consumption was slightly lower than that of the more powerful Dennis.
Traffic on our London bus test route was particularly heavy during the consecutive weekdays of our test, and this is reflected in low average speeds of 25.5km/h for the Leyland and 261on/h for the Dennis.
Both were reasonably fuel efficient with the Dennis returning 21.24lit/100km (13.3mpg) and the Olympian 23.5ln/1001m (12mpg).
The impressive Olympian fuel consumption over the longer, slower initial test period may have been slightly distorted by the gradient at our Hemel Hempstead fuel stop and the effect this had on the filling of its twin tanks. But any advantage was ruled out by our final fuel check at Heston, where care was taken to fill the tank to exactly the same level in the filler at exactly the same pump and position as at the start of the test.
• ON THE ROAD
Driving the Olympian is a predictable and not unpleasant experience. The steering is light and positive and the lock is above average. Visibility is generally good too. Manoeuvring is easy and keeping up with traffic flows is no problem. However, interior noise levels are disappointing, with far too much sound coming from body and equipment: some vibration was apparent when the engine was on tickover.
Ride is reasonable although body rattles and noise make road bumps all the more noticeable. Handling is acceptable, with a minimum of body roll; gearchanges from the ZF box are smooth and predictable.
Braking is equally smooth but it's ready and able to do its stuff as quickly as needed in an emergency. Passenger access is no problem with a 280mm step from the ground to the platform and a single step of 220mm into the saloon. A single-piece, two-leaf door is fitted. It is a little slow in operation and needed to be helped along at one point during our simulated operational running.
From the driver's point of view there is little to choose between the Dennis and the Leyland. However, we preferred the feel provided by the Dominator's larger 508mm steering wheel (the thin, 458mm Olympian wheel used to be considered a little cissy). The Dominator also handles well with good visibility but the accelerator pedal required much more effort to use than the Olympian's.
The Gardner-powered Dominator is noticeably quieter than the Cummins-powered Olympian. The ride provided by the Dominator is softer, so when unladen it is prone to bounce on undulating and bumpy road surfaces. The Dominator is quicker off the mark than the Olympian, but it has a lower top speed.
A split "South Yorkshire"-style entrance door is used on the Northern Counties body with a step of 267mm from the ground to the platform and a single step of 305mm at the front of the entrance. There is an initial step of 203mm to the single step of 254mm to the rear. A two-leaf entrance door has an interlock to prevent the bus being driven with the doors open.
Both buses are easy to keep clean, with the Northern Counties finish striking us as lighter and more attractive. Incidentally, the moulded seats at the rear of the Dominator's top deck had been whittled by vandals, while the more conventional seats on the Leyland seemed easier to clean.
• SUMMARY
Our test results demonstrate why the Leyland Olympian is still the top-selling doubledeck chassis. It is available in 9.6m and 10.6m two-axle versions as well as longer three-axle chassis which is primarily for export.
In fairness to Dennis our LG1200engined bus is the first to have this option: most Dominators are powered by the 140kW (188hp) naturally aspirated and very economical Gardner 6LXB driving through the Voith three-speed auto box. It certainly behaves like a production vehicle with performance where it is needed, low noise levels and good fuel consumption. The Dominator is also available as a 9.5 or 10.15-metre model with longer three-axle versions which, like the Olympian, are offered mainly for export.
Both British-built double-deckers provide safe, comfortable and economic public transport. Both are powered by engines that meet current and future legislation for noise and emissions.
Both are fuel efficient, easy to manage, safe and convenient to operate. Both are competitively priced in a depressed market. Both would benefit from a reduction in interior noise levels, particularly in the lower saloon. And both are offered with nationwide 24-hour parts and service support.
All of which leaves little to choose between them, and many passengers will not notice the difference. In today's cut-throat market both products are worthy contenders. At the end of the day buying decisions may well depend on humdrum details like delivery dates and, of course, the bottom line.
D by Noel Millier