What is one reason why there are restrictions on the length of semi-trailers?

Restrictions on the length of semi-trailers are primarily in place to enhance maneuverability on roads. Long semi-trailers can be more difficult to navigate through tight spaces, such as city streets, intersections, and when making turns. By having limits on their length, regulations help ensure that these vehicles can operate safely and effectively without posing a hazard to other vehicles or pedestrians. This consideration is essential for maintaining traffic flow and safety on public roads, particularly in urban areas where space is limited.

The other options, while important factors in the overall discussion about transportation and logistics, do not directly address the primary concern associated with semi-trailer length restrictions. For instance, improving fuel consumption may be a secondary effect of more efficient vehicle design, but it is not the original intent of length restrictions. Similarly, while cargo limits might benefit from an increase in trailer size, managing maneuverability remains a more pressing issue for safety and practical driving conditions. Simplifying the driving test is not relevant to trailer length regulations; instead, tests focus on driver skills applicable to various vehicle types and road situations.