  Accretion among macroscopic bodies of ~km size or larger is enhanced
significantly due to gravitational focusing. Two regimes can be distinguished.
Initially, the system experiences runaway growth, in which the gravitational
focusing factors increase, and bodies at the high-mass tail of the distribution
grow fastest. However, at some point the runaway body dynamically heats its
environment, gravitational focusing factors decrease, and runaway growth passes
into oligarchic growth. Based on the results of recent simulations, we
reconsider the runaway growth-oligarchy transition. In contrast to oligarchy,
we find that runaway growth cannot be approximated with a two component model
(of small and large bodies) and that the criterion of Ida & Makino (1993),
which is frequently adopted as the start of oligarchy, is not a sufficient
condition to signify the transition. Instead, we propose a new criterion based
on timescale arguments. We then find a larger value for the runaway
growth-oligarchy transition: from several hundreds of km in the inner disk
regions up to ~10^3 km for the outer disk. These findings are consistent with
the view that runaway growth has been responsible for the size distribution of
the present day Kuiper belt objects. Our finding furthermore outlines the
proper initial conditions at the start of the oligarchy stage.
