Depending on where you are located, call your county or city PD for guidance, in Alabama they will tell you to call a Towing company of your choice and tell them you have cars needed moved off your property, it’s considered a private property impound. 

call the local authorities , constable, sheriff or police and inform them of the abandon viehicles and they will do what must be done, unless theyre on your private property, then you can call a towman and he can remove it for you you may have to sign an impound sheet.