PCs in games always drive too fast. So you can always throw some police in hot pursuit behind them. They'll always be ready, lurking behind a convenient billboard (or tree, or whatever), to take up the chase behind the PCs. Because a vehicular chase scene isn't a real chase scene until you have multiple cop cars (or other vehicles) slamming into buildings, other vehicles, and each other due to the shenanigans of the PCs and whoever it is they're chasing.*

* Or is chasing them, if you want to play it the other way round. Which can be fun too!

Transcript

Leia: We still have to deal with the other rider!
Luke: No, he'll lead us straight to their base.
Leia: We can't let him alert them!
Luke: So we take him out just before we get there.
[SFX]: zoooom!!
Leia: How will we know?
Trooper 3: {behind them} It's okay, there's a sign.
Luke: Um...
Trooper 4: By the way, you're going a bit too fast. It's dangerous with all these trees.
[SFX]: zoooom!!
Luke: You guys know we're enemies, right?
Trooper 3: That's a bit strong.
{beat}
[SFX]: zoooooom!!
Trooper 3: But I see your point. {starts shooting}
[SFX]: Pow! Pow!
[SFX]: Pow! Pow!
Leia: Can't we be frenemies?!