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In engineering terms, the Trolleybus is clearly the most efficient 'green' public service vehicle available.

vehicle options, 12m, 15m or 18m articulated; monocoque all-flat floor -

A Trolleybus is an electrically propelled bus. Unlike an electric tram, which uses rails as a return circuit and operates with a single overhead conductor wire, a Trolleybus requires two overhead wires. Two swiveling current collectors allow a Trolleybus to operate up to about five metres either side of the wires. These collectors are spring loaded to press upward against the wires. Contact between pole and wire is by a grooved shoe containing a carbon insert that slides along the wire. Modern collectors have pneumatic equipment for the lowering and lifting.

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Trolleybus industry links -
Kiepe Elektric

Irisbus Civis/Cristalis

Kleipe trolley booms

AEG Anglo Zebra battery

AFS Trinity flywheel module

Technology pages -

Promoting quiet, clean urban transport using Overhead Electric, Zero Emission Trolleybuses -
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updated 1/2/06

Irisbus Civis
Neoplan N6121
Bombardier GLT
Berkhof Premier A T18
component options, hub motors, electronic 3-phase control, overhead -
Siemens ELFA intelligent electric drive system
Voith Turbo vehicle control unit and water-cooled braking resistor
Twin Rockwell Automotive electric drive system
ZF EE wheel hub electric drive
Magnet-Motor electric vehicle drive system
Kiepe Elektric current collection and control
Kummler+Matter overhead contact lines
Furrey+Frey overhead contact lines

Innovations. There have been considerable improvements in detail design, for example the automatic lowering of poles in the event of de-wirement or under the direct control of the driver without the driver having to leave the driving seat. And also ways of automatic re-wiring, in conjunction with special overhead fitments.

Advances in materials science and better understanding of motion dynamics have led to considerable improvements in overhead wire design. Modern suspension systems can cope easily with vehicle speeds of up to 80 kmph while being lighter in construction and less visually obtrusive. Together with the latest development in electronic power feeder systems, these advances have reduced costs, improved efficiency and free the Trolleybus from having to take junctions and crossings any more slowly than other traffic.

The latest control technology for Trolleybuses use alternating current [AC] motors, controlled by inverters that create variable voltage and frequency AC for the motors, from the DC overhead line supply. The supply voltage is between 600v and lately, 750v.

AC motors and control systems have many advantages over traditional DC systems, including greater reliability, less maintenance, greater efficiency, sophisticated control over acceleration and jerk rates. The efficiency advantages should be substantial - up to one third less power consumption than DC systems. Maintenance and reliability advantages should also be substantial - at least ten times more reliable than previous generation installations.

Comparisons. Instead of a diesel engine and transmission, a Trolleybus usually has a single electric motor, similar in size to a diesel's automatic gearbox, connected directly to the driving axle. There is no gearbox or clutch, and all gearing is done in the axle, which has a higher reduction ratio to cope with faster running Trolleybus motors.

Recent developments have permitted driving axle designs with an AC motor per wheel, or within the wheel, eliminating differentials and half shafts, permitting further simplification and greater flexibility in overall layout and facilitating low floors. Such designs, eg. the Neoplan N6121 and Irisbus Cristalis are just entering service.

Much of the engineering of Trolleybuses is, however, similar to diesel buses. Modern European Trolleybus designs e.g. the Van Hool A300 series are usually derived from proven diesel bus designs. Trolleybus electrical equipment is very flexible, consisting mainly of modules connected by flexible cables that need no special consideration for accessibility, cooling, or noise and vibration. Trolleybuses, therefore, present easier design challenges compared to diesel systems.

Attributes. Although Trolleybus suspension, steering and mechanical braking are the same as diesel buses, Trolleybuses provide the opportunity to use the motor(s) as effective electric brakes, dramatically reducing the wear and tear on mechanical braking components and tyres.

The energy generated by electric braking is either dissipated in resistors on the vehicle, or fed back into the overhead line, a system known as regenerative braking. Depending on the type of route and pattern of service, energy savings from regenerative braking can be substantial - up to one third less energy consumption.

Many Trolleybuses operate without any source of power other than the overhead wires. In modern traffic situations, some ability to operate from the overhead wires may be considered essential. Modern battery systems or auxiliary small [diesel] generator systems permit operation at 10 to 20 mph, for considerable distances, independently of overhead wires. Some new developments in battery technology, such as sodium chloride/nickel, might provide an off wire service abilty in sensitive 'heritage' areas. Specially designed flywheel units might provide acceleration 'buffers' that could reduce the overhead installation sizing.

Alternatives. Modern tramway systems in the main, operated on private right of way, are a much more environmentally friendly alternative to diesel buses. But with effective traffic management to give buses sufficient priority, electric Trolleybuses would give the public a similar travelling experience to modern trams, and at a fraction of the capital cost. Features associated with the Croydon Tramlink, such as reliable, congestion free operation, smooth, fume free ride, level boarding from raised platforms, real time information systems, etc., are all possible with modern Trolleybuses.

While buses and Trolleybuses are normally manually steered, there are advantages in automatic guidance systems over parts of routes. Automatic guidance is valuable on private alignment [busways] as it reduces the width needed for the right of way. Automatic guidance is also very useful for automatic docking at raised platforms [level entry stops] Automatic guidance on current British busways is mechanical in nature and basically not compatible with other traffic. There are at least two systems of automatic guidance available, electronic in nature, that are compatible with other traffic. One follows a white line on the road surface, the other is a buried cable as used in the access tunnel for the main Channel tunnels.

There is no environmentally friendlier way of operating urban bus routes than with Trolleybuses.

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