Hit the road/trail
Definition 1 of 1
Pro Tip 1/3Casual Tone
Used in informal situations and casual conversations, not in formal writing. 
Catch up soon, but now I've got to hit the road!
Pro Tip 2/3Urgency Implication
Often implies the need to leave promptly or beginning something without delay. 
Grab your bags, it's time to hit the road!
Pro Tip 3/3Travel Context
Especially common when talking about starting a trip or journey. 
After breakfast, we'll hit the trail and head up the mountain.