A vehicle having a main chassis (3) and a power source (4) for driving the vehicle, a drivable steer carriage (1) pivotally supporting the main chassis (3) about an at least substantially upright pivotal axis (2), the carriage including a plurality of opposed pairs of carriage wheels (5a, 7a, 9a), at least one said pair of carriage wheels being driven by a drive transmission including an input shaft (17a) at least substantially aligned with said upright pivotal axis (2) such that the power source (4) can transfer power through the input shaft (17a) to at least one carriage wheel pair.