  We introduce several new notions of (sectional) curvature bounds for
Lorentzian pre-length spaces: On the one hand, we provide convexity/concavity
conditions for the (modified) time separation function, and, on the other hand,
we study four-point conditions, which are suitable also for the non-intrinsic
setting. Via these concepts we are able to establish (under mild assumptions)
the equivalence of all previously known formulations of curvature bounds. In
particular, we obtain the equivalence of causal and timelike curvature bounds
as introduced in Kunzinger and S\"amann (Ann. Glob. Anal. Geom. 54(3):399-447,
2018).
