Travelling with a group can be exhausting. There's always a danger that you'll end up trapped for hours in a store or museum that no one wants to be at, because you're all politely waiting for each other to finish browsing. It's a form of the Abilene paradox, where everyone goes along with a bad plan to please each other.
Photo by William Warby, sculpture by Pierre Vivant
In this case, it happens because we're not used to telling people "I'm ready to go, but I don't have to go".
To prevent it, designate a point person in your group. When anyone in the group is ready to go, but also fine with staying longer, they tell the point person, "Yellow light". When everyone hits yellow light, it's time to go.
Of course, sometimes you really want to move on. In that case, say "red light" (or just, you know, "Let's get out of here") and get on out. If you've all agreed to this beforehand, it will be easier for anyone to move things forward, and harder for one person to hold everyone back.
You don't have to use my weird traffic-light terms. And you can tweak it; for example, group members can specify "I'm good for five more minutes". The important thing is that everyone in your group acknowledges the difference between "I'm ready to leave whenever" and "I'd really like to leave now". In a large group, or a multi-stop tour like a bar crawl or neighbourhood wander, this understanding can transform the entire tone of the day.
Another application is the tail end of a party or gathering. While you don't have to use the system explicitly here, you can ask yourself: Are we all sticking around because we feel obligated to close out the party together? Would most of us be happier at home? It's a good way to give yourself -- and each other -- permission to leave.
For more on the Abilene paradox in general, watch this quaint old management training video.