AMSTERDAM, Apr 2 (Reuters) Marcel Bouw always regarded his four-person bicycle as an indulgence, until it was stolen.
''We had our third child and then at the same time our bicycle was stolen. We found it was essential to have one. I cannot bring my three children to day-care on a normal bicycle,'' he said.
Until recently, people such as Bouw could not buy a bicycle other than a straightforward two-wheeler which carries a maximum of two children, one behind the handlebars and one on the back.
It is a delicate and not very safe balancing act.
In the past few years a class of young designers and welders emerged in countries such as the Netherlands and Denmark to address the inner-city transport needs of families and companies.
Their designs are taking congested cities by storm.
Riding the streets of Amsterdam, Copenhagen and Stockholm are thousands of radically new push-bikes, ranging from tricycles for day-care centres which carry eight children and low-seater bicycles with passenger-carrying trunks in front, to robust transport bikes with large containers for delivery boys.
Folding bikes and retro army bikes can be spotted everywhere.
''Bicycle design has been incredibly dormant for decades. Now there's an explosion of new forms,'' said Cees Steijn of Amazing Wheels from IJmuiden, a coastal town near Amsterdam.
They are not cheap, said Radha Meloni, 32, a shopkeeper and mother of two who paid 1,200 euros ($1,454) for a second-hand tricycle cargo bike with two benches. New ones start at 1,500 euros. It still beats the price of a decent second-hand car, let alone a new one.
''It's a big investment, but a car costs more, plus you have to buy petrol. I can park my tricycle anywhere. I'm much more flexible,'' she said.
Cargo bicycles fulfil needs that previously were met only by the car: capacity and safety.
''I have two children and so does my sister who lives nearby.
We take care of each other's children and I can't carry four on a bicycle. I needed a transport bike. It's much more stable than a bicycle,'' Meloni said.
URBAN PROFESSIONALS The first modern trikes, compact and light enough to be used by anyone, were designed by Danish bicycle-maker Christiania, named after the traffic-free enclave in Copenhagen.
The initial designers were environmentalists, but today's customer base is much bigger.
Most buyers are pragmatic urban professionals like Jouke Schouten, 33, who is a carpenter and does not own a car.
''We live in the centre and it's a nuisance to find car parking,'' said the father of two who pulls his children and the groceries in a trailer behind his bike.
High car parking fees and abundant bike lanes have ensured that 35 percent of local trips in Amsterdam are made by bike.
In other Dutch and Danish cities the percentage is even higher, according to Dutch figures. Even large enterprises, and consumers and businesses in other countries are picking up on the new bicycle trend. Coca Cola in Belgium has bought dozens of Smart Trikes from Amazing Wheels for summer sales on the promenades along the North Sea. Postmen in the Netherlands deliver mail with trikes.
Employees at chemical plants and on oil rigs in the Netherlands and Britain use rugged Truck bikes from Swedish company Monark.
Christiania and Amazing Wheels are taking orders from France, Italy, Spain, Sweden, Britain, Germany, Switzerland, Austria, Japan, Australia and the Middle East. Two-year-old WorkCycles is exporting to the United States.
''We grow with large percentages,'' says Chris van der Oord at WorkCycles. Annual sales of new tricycle and bicycle designs in the Netherlands alone have risen to tens of thousands.
BIG WHEEL TRADITION The recent International Bicycle Design Competition in Taiwan, the 10th edition of the industry's main design competition, attracted 400 entries. The winning design, announced in March, was a tricycle from French designer Yves Plattard. The runners-up were another tricycle from Korean designer Woo Seungkyun and a city bike from Chinese designer Feng Wei li.
The top three designs featured small wheels, which the traditional bike industry hates to adopt. The industry insists on a triangular frame and large wheels with low friction. They have not used any of the last 10 years of innovative bicycle designs from the competition, although today's 20 inch wheels are just as good as 28 inch ones, said juror Han Goes.
''If the industry would just be prepared to adopt 20 inch wheels, it would create a design opportunity to get rid of the triangle frame. We can move to one size fits all and there will be more room for luggage and passengers,'' he said.
''The last major new bicycle concept adopted by the industry was the mountain bike in 1985. The big bicycle makers are introvert and not market oriented.
''They design new bikes by choosing a new gear shift, a new saddle and a new colour. But the consumer doesn't care about that.
The consumer has specific needs, like bringing children to school,'' Goes added.
The breakthrough came with independent and creative bike makers, who did not wait for the big firms but were prepared to self-produce their own radical designs. Danish designers are now bringing to market a tricycle that can be converted into a normal bicycle.
With annual sales of new models already in the thousands, that should be a lesson for the big manufacturers.
''The niches addressed by these small bicycle makers aren't small at all,'' Goes said.