Starting October, some users of Tel Aviv's famous bus No. 5 bus route will be part of a futuristic experience. One of the buses to be integrated into the line for the coming year will be an electric one made by the Chinese company BYD - the first electric bus in Israel.

The passengers aren't the only ones who'll enjoy the experience. It will bring joy particularly to residents living along the city's central traffic arteries, who for at least one minute a day will enjoy the passage of a silent, non-polluting bus through their neighborhood.

It's hard to argue with the fact that buses reduce air pollution compared to private cars, for example. If a bus seats some 50 passengers, it keeps at least 25 cars off the road, significantly reducing emissions, noise pollution and traffic jams.

Still, even though the amount of pollution per bus passenger is at least four times smaller than the amount of pollution per person traveling by car, buses are among the most polluting vehicles on the roads. Motorcyclists maneuver around buses so as not to get stuck behind their exhaust pipes; drivers close their windows when idling near buses; and the residents of many neighborhoods try to the prevent soot-spreading behemoths from entering their streets, despite the importance of making buses accessible to weaker population segments.

Given the growing need around the world for public transportation solutions for crowded cities and the difficulties nations encounter - financially and engineering-wise - with installing expensive light-rail systems, bus manufacturers have started to develop new technologies to replace the standard diesel engines.

In the next few years we should know if the electric buses are a PR stunt or the start of a revolution in public transportation in Israel.

Hybrid bus: ever recharging

Buses make frequent stops at bus stops and red lights, and must accelerate fast. This makes buses an excellent fit for hybrid propulsion, where the batteries are charged every time they slow down and the electric motors assist with acceleration.

"The hybrid solution is gathering momentum among the various alternatives, and at present there are several hundred hybrid buses in commercial use around the world," says Itzik Licht, manager of the bus department at Mayer's Cars and Trucks, a Volvo importer.

Hybrid buses made by Volvo were already tested in Israel in 2011: the company's model 7700 city bus, equipped with a relatively small five-liter diesel engine supplying 210 horsepower and a momentum of 81.5 kilogram-meters per second, and an electrical engine producing 160 horsepower and the same momentum, capable of moving the bus on its own at speeds lower than 20 kilometers per hour.

The bus companies Metropoline and Kavim used the buses imported by Mayer's for three months last year. According to Licht, while a regular low-floor city bus burns one liter of fuel per every 1.6 kilometers (newer, more economical models can go 2 kilometers on a liter of fuel ), the hybrid buses averaged 2.7 kilometers for every liter of diesel.

Nonetheless, Licht notes, the cost of hybrid buses is significantly higher than regular diesel buses, making their integration into the fleets of public transportation companies conditional on government assistance. "The cost of a regular bus is 210,000 euros, whereas the cost of a hybrid bus is 330,000-340,000 euros. The difference in fuel efficiency doesn't justify the cost of buying the bus, because the bus won't return the additional investment, and this is why there's pressure on the government to provide grants," he explains.

According to Licht, without grants or other incentives that would be promised to companies operating hybrid buses, bus companies currently have no reason to buy them.

The first time there is going to be regular use of hybrid buses is in Haifa's Metronit bus rapid transport project, where the successful bus company bidder committed itself to buying six hybrid buses at the outset, as part of the conditions of the tender.

Electric buses: 250 kilometers per charge

Some feel that the solution to the high cost of buses with a dual propulsion system is ditching the diesel engine altogether. "Public transportation, where you can incorporate large batteries and the schedule of use is pre-planned, actually has features that are more compatible with electric propulsion than private vehicles," claims Doron Vadai, CEO of Clal Motors, which represents the Chinese BYD company in Israel.

According to Vadai, buses - unlike cars - only have to travel a set, limited route, usually some 200 km. a day, less than the range declared by the electric bus manufacturer, which is 250 km.

The cost of the electric buses is almost twice that of diesel engine buses, but based on assessments the fuel savings can return the investment within five to six years. "While you can't know if taxes on electricity for vehicles will go up, even today the excise tax on public transportation is low, so it doesn't seem that bus companies would be charged tax on electricity in the future either," Vadai estimates.

During the Olympic Games held four years ago in Beijing, the Chinese used a system for rapid bus battery replacements to extend the bus range even more without having to wait for the first battery to recharge overnight. Such a system would allow a bus to reach its end terminal, replace the battery quickly, and drive the route in the other direction.

The switchable system, similar to the one proposed by Better Place, seems particularly suitable to buses. But according to Vadai, such systems are very expensive and would never recoup the investment in Israel where city buses travel no more than 200 km. a day at an average speed of 15 kph.

BYD buses are not yet being sold to customers outside of China, but the model to arrive in Israel for the one-year pilot has been made to European standards. Its key challenge in Israel will actually be dealing with the heat and the power needed for the massive use of the air conditioning system.

Electric infrastructure: battery under the asphalt

The limited range of the electric bus points to a different idea for coping with the range of the electric battery: If buses move along predetermined routes, they could be supplied with energy from an external electrical source. Therefore, instead of paying for an expensive battery, one could spread a network of cables to feed the buses with electricity from outside. Trolley-type buses are powered by cable infrastructures; some can detach from the cables and travel independently for several kilometers.

The train manufacturers Siemens, Bombardier and Alstom also offer systems for wireless charging, by means of electrical induction via metal strips embedded in the road. Mickey Raviv, vice president of Bombardier Systems Israel, says that the supply infrastructure doesn't necessarily limit vehicle flexibility. "It's possible to set up the infrastructure throughout the city in such a way that buses will recharge while pulling into bus stops or while slowing down at particularly busy intersections. We're planning the system in such a way that the buses will be minimally 75 percent charged at all times, so that the infrastructure would only have to provide the rest and also allow electric supply for long distances," he says.

As for the cost, Raviv admits that it's very similar to the cost of setting up a network of light rail cables. In other words, it doesn't make financial sense to install a system only for buses, and the installation is much more complex than a simple hook-up of an electric bus to an electrical outlet. As for radiation, he guarantees that the copper panels alongside the magnetic cables protect passengers and pedestrians from hazardous exposure.

Natural gas: cheap but dangerous

The more promising development among alternative bus powering systems is one using condensed natural gas and even hydrogen-based fuel cells. No fewer than 15 million vehicles around the world are currently powered by CNG, including thousands of buses. The advantages of CNG are its low price, the almost total reduction of polluting emissions into the atmosphere, a reduction of noise, and of course the use of a local natural resource, thereby reducing dependence on fuel distillates.

But the essential drawback of CNG is the safety hazard. Experiments conducted by the police and public transportation companies in Israel in recent years raised concern about the more extensive damage to the bus and its surroundings as the result of a terrorist attack carried out on a CNG powered bus compared to a diesel powered bus. Another disadvantage is the need to build expensive infrastructure bringing the gas to fueling stations and condensing it.

In the meantime, we'll make do with Euro 6

The biggest problem with the alternatives for powering public transportation is the cost, and therefore the massive change in the fleet of buses in the foreseeable future will apparently be the application, starting at the end of 2013, of Euro Standard 6 to buses, which includes more stringent emissions requirements.

"The Euro 6 is a very tough standard, so tough that the air coming out has to be cleaner than the air going in," says Emil Kareen, CEO of commercial vehicles group Colmobil, a Mercedes importer, somewhat sarcastically. "Therefore, we'll be facing a difficult dilemma. The Euro 6 bus is not electric, but diesel-powered buses will come closer and closer to the pollution levels of electric buses, and the difference between them will shrink significantly. Only if the price of fuel continues to climb, and the cost of batteries plummets, will it make economic sense to transfer to a different powering alternative."