The positive features of trolleybuses are quite significant, and they stem almost entirely from the direct use of electrical power. It has even been suggested by dedicated advocates of this mode that trolleybus drivers are more friendly, or at least laid back, than other transit workers because they operate environmentally friendly vehicles.

• No exhaust is emitted by the electrical motor, and thus no air pollution is generated. A central power plant is needed, of course, but that is usually placed at a remote location and can be properly equipped and managed as a controlled large-scale operation. After passage of the Clean Air Act of 1990, commitment to clean vehicles became mandatory, and studies in several communities were undertaken to explore the feasibility and pollution control capabilities of trolleybuses. Los Angeles, in particular, under the strict California state requirements, looked closely at this option, but no conversions happened. While cleaner air can certainly be attained, the amount of benefits gained by such action has not been a compelling argument in the larger environmental debate in any metropolitan area.

• Quiet running characterises trolleybus operations because of the nature of pneumatic tyres and electric motors, which are not noisy even when surge power demands are placed upon them.

• Acceleration is quick because of the traction of rubber

tyres, and there are sufficient power reserves to climb steep grades, beyond the capabilities normally shown by regular buses. Advanced models incorporate regenerative braking, which feeds power back into the system instead of wasting it through brake friction or heat generation.

• Claims are being made that standard trolleybuses are durable and easy to maintain because of the simplicity of the components. That is not necessarily the case with advanced models, but the propulsion and control systems are less complex than those of comparable regular buses. However, any operating agency that already had diesel buses will want to keep the composition of its fleet as simple as possible, with not too much variety requiring special equipment, spare parts, and different skills. While it is true that the average age of a trolleybus in the United States is considerably older than that of a regular bus (16.2 versus 8.5 years), it is not entirely clear that this is due to the greater durability of trolleybuses rather than to delays in replacing the fleet.

• Petroleum-derived fuels are not used, and thus the scarce energy resources are conserved. Depending on the energy supply market at any given time and any given place, this may represent a significant savings in fuel costs. Switzerland, for example, has maintained a strong national policy of minimising dependency on fuel imports. Nepal and Canada are also rich in hydroelectric resources and try to hold on to their trolleybuses.