Cross-Talk/Interference between UART Lines on a PCB

Question

I am wondering at what distance UART lines begin to interfere with each other? And can I expect the UART lines below to function properly? The PCB board below has 6 UART lines running alongside one another (the purple traces).

Some info about the PCB below:

1. The purple traces are approximately 1mm apart 0.25mm lines. Except when red UART lines run directly above purple lines. A ground plane is in-between though.
2. 4 layer PCB top layer, inner1, inner2, and bottom are signal (red), ground, signal(purple), power planes respectively.
3. All planes are filled with a ground layer around the traces.
4. The UART lines are at 1.8V.

A close-up

Answer 1

4x spacing over a ground plane should be no problem.

I normally use a spacing of three times the trace width for normal signal traces.

Especially for UART signals that are relatively low speed there will not be an issue as most UARTS have noise rejection logic where they sample the signal three times so any coupling would be rejected anyway.

Clock and reset signals to registers are the most sensitive as any transient can permanently alter the sate of a register.

Answer 2

At 1 mm distance there will be no cross talk:

1. UART currents are really low

2. Electric and magnetic fields won't vary much in time because UART lines voltage value is constant most of the time. Current vary only when the line goes from 0 to 1 and vice versa.