Trolleybus - Advantages

Advantages

Trolleybuses are advantageous on hilly routes, as electric motors are more effective than diesel engines in providing torque at start-up, an advantage for climbing steep hills. Unlike combustion engines, electric motors draw power from a central plant and can be overloaded for short periods without damage. San Francisco and Seattle, both hilly American cities, use trolleybuses partly for this reason, another being improved air quality. Given their acceleration and braking performance, trolleybuses can outperform diesel buses on flat stretches as well.

Trolleybuses' rubber tyres have better adhesion than trams' steel wheels on steel rails, giving them better hill-climbing capability and braking. Unlike rail vehicles (where side tracks are not available), an out-of-service vehicle can be moved to the side of the road and its trolley poles lowered, allowing other trolleybuses to pass. Additionally, because they are not confined to tracks, trolleybuses can pull over to the curb as a diesel bus does, eliminating boarding islands in the middle of the street.

Like other electric vehicles, trolleybuses are more environmentally friendly in the city than fossil-fuel or hydrocarbon-based vehicles (petrol/gasoline, diesel, alcohol, etc.). Although the power is not free, having to be produced at centralised power plants with attendant transmission losses, it is produced more efficiently. Further, it is not bound to a specific fuel source and is more amenable to pollution control as a point source supply than are individual vehicles with their own engines exhausting noxious gases and particulates at street level. Moreover, some cities, like Calgary, Alberta, run their light rail networks using wind energy, which is effectively emission-free once the turbines are built and installed. Other cities, Vancouver, B.C., for instance, use hydroelectricity. A further advantage of trolleybuses is that they can generate electricity from kinetic energy while braking, a process known as regenerative braking. However, for regenerative braking to work as such, there must be another bus on the same circuit that needs power, or a way to send the excess power back to the commercial electric power system. Otherwise the braking power must be dissipated in resistance grids on the bus, when it is called "dynamic" braking. There are alternatives, such as batteries or flywheels on the bus or at the bus power station, but they add to the investment, complexity and maintenance expenses.

Unlike trams or gasoline and diesel buses, trolleybuses are almost silent, lacking the noise of an engine or of wheels on rails. Such noise as there is tends to emanate from auxiliary systems such as power steering pumps and air conditioning. Early trolleybuses without these systems were even quieter and, in the UK at least, were often referred to as the "Silent Service". The quietness did have its disadvantages though, with some pedestrians falling victim to what was also known as the "Silent Death" (in Britain) or "Whispering Death" (in Australia).

Trolleybuses are especially favoured where electricity is abundant and cheap. Examples are the extensive systems in Vancouver, Canada and Seattle, USA, both of which draw hydroelectric power from the Columbia River and other Pacific river systems. San Francisco operates its system using hydro power from the city-owned Hetch Hetchy generating plant.

As can be seen from examples in this article, electric (trolley) buses tend to be very long-lived as compared to internal combustion engine-powered buses. As the basic construction of buses has not changed much in the last fifty plus years, they can be upgraded such as when air conditioning was retrofitted to many trolleybuses when it became available. Wheelchair lifts are relatively simple to add; kneeling front suspension is a common feature of air suspension on the front axle in place of springs.

Trolleybuses are used extensively in large European cities, such as Athens, Belgrade, Bratislava, Bucharest, Budapest, Chisinau, Kiev, Lyon, Milan, Minsk, Moscow, Riga, Saint Petersburg, Sofia, Varna and Zurich, as well as smaller ones such as Arnhem, Bergen, Brest (Belarus), Cluj-Napoca, Coimbra, Gdynia, Kaunas, Lausanne, Limoges, Luzern, Parma, Piatra Neamţ, Plzeň, Prešov, Salzburg, Solingen, Szeged, Tallinn and Yalta. Realising the advantages of these zero-emission vehicles, some cities have started to expand their systems again, while others, such as Lecce and Leeds, plan to introduce new trolleybus systems.

In Cambridge, Massachusetts, the trolleybus system has survived because Harvard Station, where several bus lines terminate, is in a tunnel that was once used by trams. Although diesel buses do use the tunnel, there are limitations due to exhaust fumes. Also the trolleybuses continue to have popular support.