Vehicles carrying cylindrical bales of hay may not exceed ____________ in width.

The correct width limit for vehicles carrying cylindrical bales of hay is 144 inches. This regulation is in place to ensure safe transportation on public roads, where excessive width can pose hazards to other vehicles and infrastructure.

When vehicles exceed this width, they can become more difficult to maneuver and may obstruct traffic, leading to potential accidents. Regulations such as these are designed to balance the needs of agricultural transport with the safety of all road users.

The other options present widths that go beyond the legal limit specified for hay bales, which could lead to legal issues for operators and increased risks on the roads. Thus, understanding and adhering to this width requirement is crucial for safe and compliant transportation of cylindrical bales of hay.