The vehicles ahead of you are driving at about 30 km/h. Why are you not permitted to overtake before the road bend?

Your answer is correct because in this situation, overtaking before the road bend is not allowed for two main reasons:

1. Your overtaking distance is too long. At about 30 km/h, you need more space to safely pass the cars ahead. Because the road curves ahead, you cannot see far enough to judge whether overtaking is safe.

2. The red car in front might suddenly pull out to overtake another vehicle. This is especially risky before a bend where visibility is limited, so you must anticipate such behavior and avoid overtaking.

The third option about not being allowed to cross the lane marking does not apply here, as the lane markings are broken lines, permitting lane crossing if safe. However, due to the bend and limited visibility, overtaking is not safe.

In summary, when approaching a road bend, you must ensure you have enough clear distance to overtake safely and anticipate actions of other road users. If visibility or distance is insufficient, overtaking is prohibited. This rule helps prevent accidents in areas where you cannot clearly see oncoming traffic or road hazards.