Answer:
Build a bridge across the highway for the cats to cross safely.
Step-by-step explanation:
Since the focus is on a cost-effective and safe solution, the best option that can be perceived as the solution to the problem solution to build a bridge across the highway for the cats to cross safely.
However, deciding to move the highways to areas that do not impact the cats would be expensive since it creates an additional cost of construction.
Also, digging tunnels under the mountains for cars and trucks is not safe, and transporting the lions to a zoo where they can live the rest of their lives isn't good as it deprives them of their natural habitat.