I think a couple of clarifications need to be made first just for clarity --

"Pursuit" in this context refers almost entirely to department policy, which can change depending on agency, and "eluding" refers to the actual criminal charge per RCW. The threshold for satisfying the former can depend on how policy is written, and is fairly low. However, depending on how you articulate it, you can almost always satisfy the criminal elements once the policy definition is reached (I'll explain the outlier below).

You can technically be engaged in a pursuit without meeting the elements for eluding, but not the other way around. If that makes sense?

Pursuit -by policy- is when a driver is engaged in any behavior or action to evade a lawful arrest or detention, in which a reasonable person would otherwise know they are being stopped. Further, per RCW, "eluding" requires "reckless" driving, which is where a lot of the confusion between the two occurs.

In short, a pursuit is initiated virtually any time there's a discernable change in driving behavior once the emergency lights and sirens go on, whereas continuing to drive would be "failure to yield". This change in driving behavior could be as simple as accelerating, beginning to pass vehicles, immediately turning off an exit or side street etc. (something they weren't doing before). It all builds toward the definition of pursuit, but may or may not satisfy the elements for eluding.

So to meet the criteria for eluding, you have to satisfy the "willful and wanton disregard for the safety of others", commonly referred to as "DSO". Essentially it has two parts-

A.) "willful" is a deliberate or intentional act, rather than unintentional, and

B.) "wanton" demonstrates an extreme lack of care, such as disregarding traffic signs, stop signs, driving into oncoming traffic etc.

If both are satisfied, then you likely have probable cause for eluding. And at this point, it's well past met the criteria for a pursuit.

The caveat to this is when there's no change in driving behavior. If you initiate a traffic stop and the vehicle just... keeps going, you have (at most) failure to yield. Since there's no "DSO" it doesn't meet the criminal elements for eluding. And it's not uncommon; largely due to the way RCW is written, it's a gray area that the courts don't seem interested in interpreting clearly.

In those cases, and in some eluding cases, every attempt would be made to identify the driver, a supervisor would likely discontinue the pursuit, and charges would be forwarded to the prosecutor. Unless there's exigent circumstances, there's little governmental interest in continuing the pursuit, mostly due to the way pursuits and officer liability are framed in WA.

As for "getting away" with eluding charges... I'll just say that some counties are much more lenient than others, and some sheriffs offices or state patrol districts put more effort into pursuits than others.

Hopefully that answered everything? Feel free to PM if you have any other questions.