All this was compatible with older devices so long as there was only one authoritative timekeeper; but with urban growth and the multiplication of time signals, discrepancy brought discord and strife.

Bellevue, a fast growing city, just east of Seattle, uses a system that is gaining popularity around the intersection signals that can adjust in real time to traffic conditions.

The system as a whole has a quantized concept of time: time begins at 1 and increments every time signals propagate from one layer to the next.