Use and Enforcement: Washington State: Private Road and Sidewalk Easement

I am in Washington State and have a Private Road and Sidewalk Easement attached to my property. My property is the subservient property. There are 7 other houses that directly access there property via mine. One of the neighbors has been parking junked out cars (ie no tags, tarps over broken windows etc.) on my property but in the street that acts as the easement and refused to move the vehicles when asked by me politely. The filed paperwork with the county does not define accepted use of the easement but just lists the legal description. I have called the police and the county but both deny jurisdiction because it is a private road. One of my neighbors is trying to sell their home and was told by the realtor that the junked cars on the road would make it hard to sell. it does look pretyy terrible. It has also made it to where there is no room for visitors to park in the neighborhood. I am trying to resolve this without legal action. Would sending a letter to all neighbors that parking there will be considered trespassing and their cars will be towed at there expense as well as posting signs protect me from legal liability if I have their vehicles towed? Thank you in advance for any help you may be able to rovide.

Use and Enforcement: Washington State: Private Road and Sidewalk Easement