Both the KED model universe and the Milne kinematic model universes, if extrapolated to the Planck epoch, tend approximately to the Planck unit length.
At the Planck epoch the classical Schwarzschild black hole radius and the de Broglie--Compton quantum wavelength [gamma] = h/mc for Planck mass particles (maximons) turned out to be equal ones (Sapar, 1977).
Approaching the Planck epoch is therefore associated with the signature change from Lorentzian space-time to Euclidean four-dimensional space .
In LQC, which is an alternative to CDT, a gravitational second-order phase transition may explain a signature change in the Planck epoch. In the presented toy model, the universe originates just at the critical point.