What do bridge formulas help ensure concerning roadways?

Answer: A — They prevent overloaded bridges and roadways

Bridge formulas are mathematical equations used to calculate the maximum allowable weight of a vehicle that can safely cross a bridge based on its capacity and design. These formulas take into account various factors, including the number of axles on the vehicle and the spacing between them, to prevent overloading. When vehicles exceed the weight limits established by bridge formulas, it can lead to significant structural damage to the bridge and potentially cause safety hazards for both the vehicle and other road users. Therefore, by adhering to these formulas, transportation authorities can ensure that bridges and roadways maintain their integrity and continue to function safely, thereby preventing accidents related to structural failure. In relation to the other choices, increasing speed limits, determining the number of lanes, or ensuring compliance with traffic designs do not specifically pertain to the primary purpose of bridge formulas. These functions involve different regulations and design principles that are not directly addressed by the weight restrictions imposed by bridge formulas.