The Dutch company Biermann in Nieuw Vennep to the south-west of Amsterdam has specialised in the conversion of vehicles for the physically handicapped for more than 60 years. The main focus is on so-called WAVs (Wheelchair Accessible Vehicles). The company has an international sales and service network. The main customers are wheelchair users, taxi operators, rental companies, hospitals, care homes and other organisations.

The vehicle used as the basis for Bierman conversions is the long version of the Mercedes-Benz Citan. The company installs a recessed GRP floor measuring 1700 x 800 mm in the rear. The maximum interior height is 1500 mm. Access is via a 1400 mm long aluminium ramp. An 800 mm long ramp is sufficient if an electro-hydraulically lowerable rear end or a gas-pressure strut is installed.

The wheelchair is fixed in place by a four-point system, its occupant being held by a three-point safety belt. As the recessed floor is slightly offset to the left, space for an additional passenger seat is created in the middle row. If a tailgate is installed in place of hinged rear doors, the original bumper is mounted on the tailgate extension. In this case Bierman uses extended gas-pressure struts for a wider tailgate opening angle. The entire conversion is approved according to the current standards and regulations.