To say "safe travels" in French, you can use the phrase "bon voyage." This expression is commonly used to wish someone a pleasant journey. If you want a more formal or heartfelt way to convey your wishes, you might say, "je vous souhaite un bon voyage," which means "I wish you a good trip."
"Bon voyage" is appropriate for both casual and formal contexts, whether you're saying goodbye to friends, family, or colleagues. It's a versatile phrase that captures your hopes for their safety and enjoyment during their travels.