11 will bear against the cab 1 thereby preventing the door 5 from pivoting downwards into a locking position if the operator wishes to close the door 5 they simply engage the release handle 9 which in turn operates the locking pin 11 which withdraws into the door thereby allowing the door 5 to be pivoted downwards to a closed position in a closed position the locking pin will bear against the cab once more a biasing means not shown is provided to urge the door from a substantially horizontal closed position to an upright open position the biasing means comprises a torsion spring which acts to rotate the door to an open vertical position the torsion spring provides a smooth action and also forces the door to latch in an upright position as an alternative to the torsion spring a gas strut or other similar means may be used as the biasing means it is envisaged that instead of the locking pin 11 bearing directly against the cab a pin receiving hole could be provided on the cab to receive the locking pin when the door is in either an open or a closed configuration alternatively a pair of holes could be provided one to receive the locking pin when the door is in a closed position and one to receive the locking pin when the door is in an open configuration in another still embodiment a plurality of pin receiving holes may be provided to allow for a degree of adjustability of the door so that it may be positioned relative the driver to suit the height of the driver operating the vehicle in the embodiment shown the cab 1 is a framework structure comprising a.