The Rollfiets (known as the Duet in English-speaking countries) makes all this possible with a design of the highest quality, refined over more than 18 years. The latest 'Rollfiets NT' incorporates plenty of new technology - it is even more stable, more compact for transport and is adjustable to fit an even wider range of riders and passengers.

The wheelchair is based on an aluminium chassis, and is a fully-functional vehicle in its own right. The seat is 2cm lower than before, making transfers easier and improving stability. Headrests, arm supports and other specialised adaptations are available to suit almost any need, and the whole ABS seat-shell can be quickly removed, or swapped over for different passengers. The back support can be adjusted for angle, or folded forward as on a racing wheelchair. Two custom-made drum brakes ensure power ful stopping, and a parking brake is fitted.

The 'bicycle' rear half attaches in seconds, and is normally equipped with a seven-speed Sachs hub gear. There are other options - a 'Mountain-Drive' two-speed bottom-bracket gearbox (see the 'Accessories' section in this Encycleopedia) and five-speed hub, or a power-assisted version with a small electric motor.

The cost of a Rollfiets is covered in many countries by various health insurance or social security provisions. Support for applicants to such schemes, and much more, is offered by the 'Rollfiets Club' - an active association of thousands of enthusiastic users worldwide. Elderly, infirm or partly-disabled riders may be able to pedal for themselves, but find a two-wheeler uncomfortably wobbly. A tricycle may be the answer, and Robert Hoening offers a choice of two: the recumbent Trio and the upright T-Bikes.

The Trio will steer perfectly straight even at the lowest speeds, yet which has the performance and braking to take full advantage of whatever amount of power the rider puts in. The relaxed seating position and rear suspension ensure comfort, even on longer journeys, and both handlebar and seat have a wide range of adjustment. A version is available for those with the use of only one hand. The Trio can be fitted with a range of special adaptations to suit other particular needs.

Standard equipment includes 21- speed Sachs gearing, full lighting, mudguards and a large carrier between the 26" (559) rear wheels. Braking is by Magura rim brakes on the front 20" (406) wheels, and two hydraulic discs at the rear. A parking brake makes mounting and dismounting steady and secure, and the handling is safe and predictable. The standard Trio weighs about 25kg, and a power ful motor version with a 500W engine and - according to the recent extra-energy test - a range of more than 150 km, is also available.

Another option for those wishing to resume their cycling on three wheels is a T-Bike (above). Well-known and widely respected for many years in the Netherlands, these tricycles are now being distributed worldwide (outside the Netherlands) by Robert Hoening. With two wheels at the front, obstacles can be negotiated with the widest part of the bike fully visible - and there are major benefits for stability, especially when braking. There are four sizes for all ages, and a host of possible modifications, including two motor-assisted versions (internal combustion and electric). The space between the front wheels can be filled with a capacious luggage basket.

Robert Hoening also distributes the delightful Copilot: a tandem which allows a disabled or partly-active child to take part in the steering process, giving them the therapeutically important sensation of being in control. The adult rider has wider handlebars, and so can override any mistakes or wilfulness on the part of the youngster.