Which of the following is NOT a factor in determining safe speed down a downgrade?

When determining a safe speed while going down a downgrade, various factors play a significant role in ensuring the safety of the vehicle and its occupants. Key considerations include road conditions, which affect traction and handling; weather, which can impact visibility and road surface conditions; and the length of the grade, which influences braking distance and the amount of time a vehicle will be traveling downhill.

The presence of pedestrians, while an important factor in overall traffic safety, is not directly tied to the factors specifically concerning the vehicle's speed on a downgrade. Pedestrians are generally more relevant in urban settings or areas with high foot traffic, but when assessing safe operating speeds on descents, the focus remains primarily on the vehicle's interaction with the road, weather, and grade characteristics. Thus, the correct answer reflects that pedestrians do not pertain to the specific engineering and physics considerations that dictate safe speeds on downgrades.