A trolleybus is generally a standard motor bus with poles, electric controls and
motors in place of an internal combustion engine and associated systems. It
relies on an external source of power - two overhead wires which the poles
contact (for more information see the article
on electric vehicle technologies).
Vancouver operates a large fleet of trolleybuses. All 244 buses were built in
1982 and 1983. BC Transit currently plans to not buy any trolleybuses at least
until the year 2003. Transport Action BC advocates not just retaining but
expanding the existing trolleybus
system, and would like in the short term to see BC Transit buy articulated
trolleybuses to improve service and reduce crowding on existing, heavily used
routes.
Issues - trolleybus versus motor bus
The major advantages of trolleybuses over buses powered by internal
combustion engines are:
- no direct emissions
- more energy efficient
- quieter
- better acceleration
- less maintenance intensive (less brake wear, motors last longer and do not
require overhaul every 5 years)
- longer lasting
The major disadvantage is the requirement to run under wires. The cost of
installing the wires, support structures and electric substations is a
significant sunk cost which needs to be justified. In addition, trolleybuses are
significantly more expensive to buy than diesel buses, presumably due mostly to
the relative market size for the two types of bus. Note, however, that
trolleybuses are expected to last longer - in Vancouver the trolleybuses are
expected to last 30 years, whereas diesel buses are expected to last 20 years.
Another disadvantage of trolleybuses is the requirement to pass slowly under
switches. However, switches are most often at intersections where buses need to
make a stop anyway.
Other differences are not clearly advantages or disadvantages. Some people
think overhead wires are unsightly. Others are not bothered by them and some
view them as a visible investment in public transit. Some people consider the
inability of trolleybuses to pass each other a disadvantage. Others prefer that
buses not be able to play leapfrog.
Latest developments
The most significant recent advance in technology is the use of brushless AC
motors, which require less maintenance than DC motors. This has been made
possible by advances in solid state electronics.
The low floor bus has become very popular
as well, for the same reasons as for low floor
light rail vehicles.
Dual mode buses are being used in many locations to allow service to areas
without overhead wires but still provide quiet, electrically powered service on
the busiest part of the route. These buses include both a diesel engine and
electric (traction) motors. In some designs the diesel engine is used as an
electrical generator, in others the electric motor powers one axle (of a 3 axle
articulated bus) and the diesel powers the other. Seattle has a fleet of 236 of
the latter type - these are generally used in electric mode through the downtown
tunnel only.
Click here to see the electric trolleybus
manufacturers and orders.
What's out there today?
The following lists some articulated trolleybuses the author has information
on. This list is far from complete and at present lists mostly dual mode buses.
Each description includes the manufacturer, city or cities in which the bus
is used, the date the bus type was first delivered, the total number in service
or on order, floor height(s), the bus' length, width and mass, the number of
motors and total power, and the number of seats and total capacity including
standees (as claimed by manufacturer - I don't think this is the standard 4
standees per square metre, so take it with a grain of salt).
Low floor
MAN, Kiepe
Innsbruck, 1989, ?
floor height ? mm
17.4 m x 2.5 m
15 tonnes
1 traction motor (149 kW) driving 3rd axle, 1 diesel engine used as generator
(49.8 kW)
Seats 47, total 142
NAW, Hess, ABB
?, 1991, 1 (prototype)
320 mm (front door), 340 mm (second door), 575 mm (back door)
17.77 m x 2.5 m
17.4 tonnes
2 traction motors (89 kW each), 1 diesel engine used as generator
Seats 40, total 143
Van Hool AG300T
17.93 m x 2.49 m
16.8 tonnes
1 traction motor (150 kW), 1 diesel engine used as generator (150 kW)
Seats 42, total 146
High floor
Volvo, ABB
Fribourg, 1988, 12
745 mm (front and second door), 825 mm (third and back door)
17.68 m x 2.5 m
17.9 tonnes
1 traction motor (152 kW) driving 3rd axle, 1 diesel engine driving 2nd axle
Seats 35, total 140
NAW, Hess, ABB
Schaffhausen, 1991, 8
606 mm (front door), 761 mm second and back doors
17.85 m x 2.5 m
17.4 tonnes
2 traction motors (89 kW each), 1 diesel engine used as generator
Seats 42, total 149
Daimler-Benz, ABB
Zürich, 1988, 36
710 mm
17.4 m x 2.5 m
16.4 tonnes
1 traction motor (152 kW) driving 3rd axle, 1 diesel engine driving 2nd axle for
emergency operation
Seats 50, total 166
James Strickland
|