Irrespective of the story that you have in mind, occasionally you will wish to add a twist or an event that could heighten the readers interest. There are all manner of things you could use and in some ways that can be the difficulty because you are spoilt for choice. There are some ideas below.
Cows on the motorway!
Is your fugitive, hero or quarry trapped in the hold up caused by cows on the motorway? That could add to the tension.
In many tales there is a restaurant scene. The film 'Hitman' starring Timothy Oliphant, has such a scene where in fact he has gone to eliminate and adversary on the way to his ultimate quarry but he takes the girl and we are distracted from the action by the conversation between the two of them. It serves the purpose of lightening the atmosphere briefly. However, it does serve a purpose as we find out more of Oliphant's skills.
The musical Les Miserables is quite dark and I don't mind admitting I cried buckets but I also remember the clever way that the director of the stage show introduced the Innkeeper and his wife, which had the effect of lightening the atmosphere however briefly. The original story by Hugo does have the same innkeeper and wife, where Cosette is left by her mother Fantine, but there is no humour in that part of the book unlike the musical. In my opinion the film fails in that one department.
In my Steele novels I try and introduce the human element into the stories to enhance the readers knowledge of Patrick Steele, Naomi Kobayashi and Takuo Sumisu. In the first book with his Japanese sensei it is via a trip to Osaka to meet his controlling family that breaks away from the main thrust of the tale.
However, you write and progress your stories, irrespective of genre I think adding an interlude which is seemingly innocuous, perhaps even unimportant, can give the reader a 'breather'. It has a number of valuable possibilities attached,
1. The breather I mentioned.
2. Informing the reader about aspects of the central character that will be useful later.
3. Providing added unexpected tension.
4. Shows the reader what a clever writer you are!
This is a strategy that you may already use or perhaps not, but which ever is the case, it is there and free of charge.