What should be checked when approaching an underpass or low clearance area?

Answer: B — If the underpass height is marked

When approaching an underpass or low clearance area, checking if the underpass height is marked is crucial for ensuring safe navigation. Height markings provide critical information that helps determine if the apparatus can safely pass under the structure without risk of collision. This is particularly important for aerial fire apparatus, which can be significantly taller than many other vehicles. Accurately assessing the height allows the driver/operator to make informed decisions, such as whether to proceed or take an alternative route. Ignoring these markings could lead to severe damage to the apparatus, obstruction of traffic, or even injury. Therefore, understanding and adhering to the height information is key to safe operation and navigation in low clearance areas.