Axle shaft assemblies for use with a vehicle include a shaft formed from a first material having a first modulus of elasticity for providing the shaft with a flexibility adapted to withstand side impacts and resist deformation. A first end member can be engaged with a first end of the shaft, and a second end member can be engaged with the second end of the shaft. The end members can be formed from a second material having a second modulus of elasticity greater than the first, such that the end members are adapted to withstand a rotational force. The end members can include splined connectors, hub flanges, and other similar components. The resulting axle shaft assembly can thereby include modular combinations of materials having low and high moduli of elasticity.

A traveling vehicle includes a body having a seat in which a user can sit, and a plurality of wheels provided to the body, the height of a seat surface of the seat being lower than the upper parts of the plurality of wheels. In the body, a battery accommodation section that accommodates a battery is provided to a side of the seat. At least part of the battery accommodation section overlaps the seat in a side view of the body, and the battery accommodation section is tilted such that a rear end part is positioned higher than a front end part.