The difficult purchasing decision new motorcoach buyers are facing this year whether to buy buses equipped with new 2007-reduced emissions engines -- is going to be infinitely more difficult in three years.

It has become increasingly clear in the past few weeks that buyers will face choices in 2010 unlike any they have faced in more than a generation.

Two major engine makers, Cummins Inc. and Navistar International, have announced their intention to comply with the next change in Environmental Protection Agency emission requirements by updating the same technology they've used since 2004 to meet the first two steps of a three-step program.

Some form of this technology, exhaust gas recirculation, is currently in use by all major U.S. heavy-duty diesel engine makers.

Volvo, which begins supplying engines to Prevost Car next year (see story on page one), and Detroit Diesel, the major motorcoach industry engine supplier, have said they will add selective catalytic reduction to meet the 2010 restrictions on nitrogen oxides.

Caterpillar has yet to announce its technology path.

The key characteristic of SCR is that it injects a mixture of urea and water into the exhaust stream to cleanse residual NOx emissions. This requires vehicles using this technology to have a storage tank for the urea solution. Drivers will have to ensure the tank has fluid in it or the bus or truck will lose power.

Concerns have been raised about supplies of urea and that the extra tank will add weight and cost to new buses and trucks.

At the same time, some analysts are saying that competing technologies could be good for buyers, offering operators a choice and encouraging suppliers to keep prices down.

If competing technologies reduce buyer anxiety and give them less cause to rush to update their equipment with existing technology, so as to avoid the new engines, that is seen as being good for everyone engine makers, coach builders and other suppliers.

What wouldnt be good is if the situation creates the kind of split that divided video cassette recorders between the Beta and VHS formats in the early 1980s. Many consumers withheld purchases, waiting for the market to decide which format would survive, on the theory that both couldn't make it. And, of course, by 1985 VHS had won.

Certainly a lot will be written and said during the next three years as announcements are made, testing of 2010 engines progresses, and potential buyers make their views known.